What is Citalopram?

Introduction

Citalopram, sold under the brand name Celexa among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class.

It is used to treat major depressive disorder, obsessive compulsive disorder, panic disorder, and social phobia. The antidepressant effects may take one to four weeks to occur. It is taken by mouth.

Common side effects include nausea, trouble sleeping, sexual problems, shakiness, feeling tired, and sweating. Serious side effects include an increased risk of suicide in those under the age of 25, serotonin syndrome, glaucoma, and QT prolongation. It should not be used in persons who take or have recently taken a MAO inhibitor. Antidepressant discontinuation syndrome may occur when stopped. There are concerns that use during pregnancy may harm the foetus.

Citalopram was approved for medical use in the United States in 1998. It is on the World Health Organisation’s List of Essential Medicines. It is available as a generic medication. In 2019, it was the 30th most commonly prescribed medication in the United States, with more than 21 million prescriptions.

Brief History

Citalopram was first synthesized in 1972 by chemist Klaus Bøgesø and his research group at the pharmaceutical company Lundbeck and was first marketed in 1989 in Denmark. It was first marketed in the US in 1998. The original patent expired in 2003, allowing other companies to legally produce and market generic versions.

Medical Uses

Depression

In the United States, citalopram is approved to treat major depressive disorder. Citalopram appears to have comparable efficacy and superior tolerability relative to other antidepressants. In the National Institute for Health and Clinical Excellence ranking of ten antidepressants for efficacy and cost-effectiveness, citalopram is fifth in effectiveness (after mirtazapine, escitalopram, venlafaxine, and sertraline) and fourth in cost-effectiveness. The ranking results were based on a 2009 meta-analysis by Andrea Cipriani; an update of the analysis in 2018 produced broadly similar results.

Evidence for effectiveness of citalopram for treating depression in children is uncertain.

Panic Disorder

Citalopram is licensed in the UK and other European countries for panic disorder, with or without agoraphobia.

Other

Citalopram may be used off-label to treat anxiety, and dysthymia, premenstrual dysphoric disorder, body dysmorphic disorder, and obsessive-compulsive disorder (OCD).

It appears to be as effective as fluvoxamine and paroxetine in OCD. Some data suggest the effectiveness of intravenous infusion of citalopram in resistant OCD. Citalopram is well tolerated and as effective as moclobemide in social anxiety disorder. There are studies suggesting that citalopram can be useful in reducing aggressive and impulsive behaviour. It appears to be superior to placebo for behavioural disturbances associated with dementia. It has also been used successfully for hypersexuality in early Alzheimer’s disease.

A meta-analysis, including studies with fluoxetine, paroxetine, sertraline, escitalopram, and citalopram versus placebo, showed SSRIs to be effective in reducing symptoms of premenstrual syndrome, whether taken continuously or just in the luteal phase. For alcoholism, citalopram has produced a modest reduction in alcoholic drink intake and increase in drink-free days in studies of alcoholics, possibly by decreasing desire or reducing the reward.

While on its own citalopram is less effective than amitriptyline in the prevention of migraines, in refractory cases, combination therapy may be more effective.

Citalopram and other SSRIs can be used to treat hot flashes.

A 2009 multisite randomised controlled study found no benefit and some adverse effects in autistic children from citalopram, raising doubts whether SSRIs are effective for treating repetitive behaviour in children with autism.

Some research suggests citalopram interacts with cannabinoid protein-couplings in the rat brain, and this is put forward as a potential cause of some of the drug’s antidepressant effect.

Administration

Citalopram is typically taken in one dose, either in the morning or evening. It can be taken with or without food. Its absorption does not increase when taken with food, but doing so can help prevent nausea. Nausea is often caused when the 5HT3 receptors actively absorb free serotonin, as this receptor is present within the digestive tract. The 5HT3 receptors stimulate vomiting. This side effect, if present, should subside as the body adjusts to the medication.

Citalopram is considered safe and well tolerated in the therapeutic dose range. Distinct from some other agents in its class, it exhibits linear pharmacokinetics and minimal drug interaction potential, making it a better choice for the elderly or comorbid patients.

Adverse Effects

Sexual dysfunction is often a side effect with SSRIs.

Citalopram theoretically causes side effects by increasing the concentration of serotonin in other parts of the body (e.g. the intestines). Other side effects, such as increased apathy and emotional flattening, may be caused by the decrease in dopamine release associated with increased serotonin. Citalopram is also a mild antihistamine, which may be responsible for some of its sedating properties.

Other common side effects of citalopram include drowsiness, insomnia, nausea, weight changes (usually weight gain), increase in appetite, vivid dreaming, frequent urination, dry mouth, increased sweating, trembling, diarrhoea, excessive yawning, severe tinnitus, and fatigue. Less common side effects include bruxism, vomiting, cardiac arrhythmia, blood pressure changes, dilated pupils, anxiety, mood swings, headache, hyperactivity and dizziness. Rare side effects include convulsions, hallucinations, severe allergic reactions and photosensitivity. If sedation occurs, the dose may be taken at bedtime rather than in the morning. Some data suggests citalopram may cause nightmares. Citalopram is associated with a higher risk of arrhythmia than other SSRIs.

Withdrawal symptoms can occur when this medicine is suddenly stopped, such as paraesthesia, sleeping problems (difficulty sleeping and intense dreams), feeling dizzy, agitated or anxious, nausea, vomiting, tremors, confusion, sweating, headache, diarrhoea, palpitations, changes in emotions, irritability, and eye or eyesight problems. Treatment with citalopram should be reduced gradually when treatment is finished.

Citalopram and other SSRIs can induce a mixed state, especially in those with undiagnosed bipolar disorder.  According to an article published in 2020, one of the other rare side effects of Citalopram could be triggering visual snow syndrome; which does not resolve after the discontinuation of the medicine.

Sexual Dysfunction

Some people experience persistent sexual side effects after they stop taking SSRIs. This is known as Post-SSRI Sexual Dysfunction (PSSD). Common symptoms in these cases include genital anaesthesia, erectile dysfunction, anhedonia, decreased libido, premature ejaculation, vaginal lubrication issues, and nipple insensitivity in women. The prevalence of PSSD is unknown, and there is no established treatment.

Abnormal Heart Rhythm

In August 2011, the US Food and Drug Administration (FDA) announced, “Citalopram causes dose-dependent QT interval prolongation. Citalopram should no longer be prescribed at doses greater than 40 mg per day”. A further clarification issued in March 2012, restricted the maximum dose to 20 mg for subgroups of patients, including those older than 60 years and those taking an inhibitor of cytochrome P450 2C19.7.

Endocrine Effects

As with other SSRIs, citalopram can cause an increase in serum prolactin level. Citalopram has no significant effect on insulin sensitivity in women of reproductive age and no changes in glycaemic control were seen in another trial.

Exposure in Pregnancy

Antidepressant exposure (including citalopram) during pregnancy is associated with shorter duration of gestation (by three days), increased risk of preterm delivery (by 55%), lower birth weight (by 75 g), and lower Apgar scores (by <0.4 points). Antidepressant exposure is not associated with an increased risk of spontaneous abortion. It is uncertain whether there is an increased prevalence of septal heart defects among children whose mothers were prescribed an SSRI in early pregnancy.

Interactions

Citalopram should not be taken with St John’s wort, tryptophan or 5-HTP as the resulting drug interaction could lead to serotonin syndrome. With St John’s wort, this may be caused by compounds in the plant extract reducing the efficacy of the hepatic cytochrome P450 enzymes that process citalopram. It has also been suggested that such compounds, including hypericin, hyperforin and flavonoids, could have SSRI-mimetic effects on the nervous system, although this is still subject to debate. One study found that Hypericum extracts had similar effects in treating moderate depression as citalopram, with fewer side effects.

Tryptophan and 5-HTP are precursors to serotonin. When taken with an SSRI, such as citalopram, this can lead to levels of serotonin that can be lethal. This may also be the case when SSRIs are taken with SRAs (serotonin releasing agents) such as in the case of MDMA. It is possible that SSRIs could reduce the effects associated due to an SRA, since SSRIs stop the reuptake of Serotonin by blocking SERT. This would allow less serotonin in and out of the transporters, thus decreasing the likelihood of neurotoxic effects. However, these concerns are still disputed as the exact pharmacodynamic effects of citalopram and MDMA have yet to be fully identified.[citation needed]

SSRIs, including citalopram, can increase the risk of bleeding, especially when coupled with aspirin, NSAIDs, warfarin, or other anticoagulants. Citalopram is contraindicated in individuals taking MAOIs, owing to a potential for serotonin syndrome.

Taking citalopram with omeprazole may cause higher blood levels of citalopram. This is a potentially dangerous interaction, so dosage adjustments may be needed or alternatives may be prescribed.

SSRI discontinuation syndrome has been reported when treatment is stopped. It includes sensory, gastrointestinal symptoms, dizziness, lethargy, and sleep disturbances, as well as psychological symptoms such as anxiety/agitation, irritability, and poor concentration. Electric shock-like sensations are typical for SSRI discontinuation. Tapering off citalopram therapy, as opposed to abrupt discontinuation, is recommended in order to diminish the occurrence and severity of discontinuation symptoms. Some doctors choose to switch a patient to Prozac (fluoxetine) when discontinuing citalopram as fluoxetine has a much longer half-life (i.e. stays in the body longer compared to citalopram). This may avoid many of the severe withdrawal symptoms associated with citalopram discontinuation. This can be done either by administering a single 20 mg dose of fluoxetine or by beginning on a low dosage of fluoxetine and slowly tapering down. Either of these prescriptions may be written in liquid form to allow a very slow and gradual tapering down in dosage. Alternatively, a patient wishing to stop taking citalopram may visit a compounding pharmacy where their prescription may be re-arranged into progressively smaller dosages.

Overdose

Overdosage may result in vomiting, sedation, disturbances in heart rhythm, dizziness, sweating, nausea, tremor, and rarely amnesia, confusion, coma, or convulsions.  Overdose deaths have occurred, sometimes involving other drugs, but also with citalopram as the sole agent. Citalopram and N-desmethylcitalopram may be quantified in blood or plasma to confirm a diagnosis of poisoning in hospitalised patients or to assist in a medicolegal death investigation. Blood or plasma citalopram concentrations are usually in a range of 50-400 μg/l in persons receiving the drug therapeutically, 1000-3000 μg/l in patients who survive acute overdosage and 3-30 mg/l in those who do not survive. It is the most dangerous of SSRIs in overdose.

Suicidality

In the United States, citalopram carries a boxed warning stating it may increase suicidal thinking and behaviour in those under age 24.

Stereochemistry

Citalopram has one stereocentre, to which a 4-fluoro phenyl group and an N, N-dimethyl-3-aminopropyl group bind. As a result of this chirality, the molecule exists in (two) enantiomeric forms (mirror images). They are termed S-(+)-citalopram and R-(–)-citalopram.

Citalopram is sold as a racemic mixture, consisting of 50% (R)-(−)-citalopram and 50% (S)-(+)-citalopram. Only the (S)-(+) enantiomer has the desired antidepressant effect. Lundbeck now markets the (S)-(+) enantiomer, the generic name of which is escitalopram. Whereas citalopram is supplied as the hydrobromide, escitalopram is sold as the oxalate salt (hydrooxalate). In both cases, the salt forms of the amine make these otherwise lipophilic compounds water-soluble.

Metabolism

Citalopram is metabolised in the liver mostly by CYP2C19, but also by CYP3A4 and CYP2D6. Metabolites desmethylcitalopram and didesmethylcitalopram are significantly less energetic and their contribution to the overall action of citalopram is negligible. The half-life of citalopram is about 35 hours. Approximately 80% is cleared by the liver and 20% by the kidneys. The elimination process is slower in the elderly and in patients with liver or kidney failure. With once-daily dosing, steady plasma concentrations are achieved in about a week. Potent inhibitors of CYP2C19 and 3A4 might decrease citalopram clearance. Tobacco smoke exposure was found to inhibit the biotransformation of citalopram in animals, suggesting that the elimination rate of citalopram is decreased after tobacco smoke exposure. After intragastric administration, the half-life of the racemic mixture of citalopram was increased by about 287%.

Society and Culture

Brand Names

Citalopram is sold under these brand names:

  • Akarin (Denmark, Nycomed).
  • C Pram S (India).
  • Celapram (Australia and New Zealand).
  • Celexa (US and Canada, Forest Laboratories, Inc.).
  • Celica (Australia).
  • Ciazil (Australia and New Zealand).
  • Cilate (South Africa).
  • Cilift (South Africa).
  • Cimal (South America, by Roemmers and Recalcine).
  • Cipralex (South Africa).
  • Cipram (Denmark and Turkey, H. Lundbeck A/S).
  • Cipramil (Australia, Brazil, Belgium, Chile, Finland, Germany, Netherlands, Iceland, Ireland, Israel, New Zealand, Norway, Russia, South Africa, Sweden, and the United Kingdom).
  • Cipraned, Cinapen (Greece).
  • Ciprapine (Ireland).
  • Ciprotan (Ireland).
  • Citabax, Citaxin (Poland).
  • Cital (Poland).
  • Citalec (Czech Republic and Slovakia).
  • Citalex (Iran and Serbia).
  • Citalo (Australia, Egypt, and Pakistan).
  • Citalopram (Canada, Denmark, Finland, Germany, Ireland, New Zealand, Spain, Sweden, Switzerland, United Kingdom, the US).
  • Citol (Russia).
  • Citox (Mexico).
  • Citrol (Europe and Australia).
  • Citta (Brazil).
  • Dalsan (Eastern Europe).
  • Denyl (Brazil).
  • Elopram (Italy).
  • Estar (Pakistan).
  • Humorup (Argentina).
  • Humorap (Peru, Bolivia).
  • Lopraxer (Greece).
  • Oropram (Iceland, Actavis).
  • Opra (Russia).
  • Pram (Russia).
  • Pramcit (Pakistan).
  • Procimax (Brazil).
  • Recital (Israel, Thrima Inc. for Unipharm Ltd.).
  • Sepram (Finland).
  • Seropram (various European countries, including Czech Republic).
  • Szetalo (India).
  • Talam (Europe and Australia).
  • Temperax (Argentina, Chile, and Peru).
  • Vodelax (Turkey).
  • Zentius (South America, by Roemmers and Recalcine).
  • Zetalo (India).
  • Cipratal (Kuwait, GCC).
  • Zylotex (Portugal).

European Commission Fine

On 19 June 2013, the European Commission imposed a fine of €93.8 million on the Danish pharmaceutical company Lundbeck, plus a total of €52.2 million on several generic pharmaceutical-producing companies. This was in response to Lundbeck entering an agreement with the companies to delay their sales of generic citalopram after Lundbeck’s patent on the drug had expired, thus reducing competition in breach of European antitrust law.

An Overview of the Biology of Depression

Introduction

Scientific studies have found that different brain areas show altered activity in people with major depressive disorder (MDD), and this has encouraged advocates of various theories that seek to identify a biochemical origin of the disease, as opposed to theories that emphasize psychological or situational causes.

Factors spanning these causative groups include nutritional deficiencies in magnesium, vitamin D, and tryptophan with situational origin but biological impact. Several theories concerning the biologically based cause of depression have been suggested over the years, including theories revolving around monoamine neurotransmitters, neuroplasticity, neurogenesis, inflammation and the circadian rhythm. Physical illnesses, including hypothyroidism and mitochondrial disease, can also trigger depressive symptoms.

Neural circuits implicated in depression include those involved in the generation and regulation of emotion, as well as in reward. Abnormalities are commonly found in the lateral prefrontal cortex whose putative function is generally considered to involve regulation of emotion. Regions involved in the generation of emotion and reward such as the amygdala, anterior cingulate cortex (ACC), orbitofrontal cortex (OFC), and striatum are frequently implicated as well. These regions are innervated by a monoaminergic nuclei, and tentative evidence suggests a potential role for abnormal monoaminergic activity.

Genetic Factors

Difficulty of Gene Studies

Historically, candidate gene studies have been a major focus of study. However, as the number of genes reduces the likelihood of choosing a correct candidate gene, Type I errors (false positives) are highly likely. Candidate genes studies frequently possess a number of flaws, including frequent genotyping errors and being statistically underpowered. These effects are compounded by the usual assessment of genes without regard for gene-gene interactions. These limitations are reflected in the fact that no candidate gene has reached genome-wide significance.

Gene Candidates

5-HTTLPR

The 5-HTTLPR, or serotonin transporter promoter gene’s short allele, has been associated with increased risk of depression; since the 1990s, however, results have been inconsistent. Other genes that have been linked to a gene-environment interaction include CRHR1, FKBP5 and BDNF, the first two of which are related to the stress reaction of the HPA axis, and the latter of which is involved in neurogenesis. Candidate gene analysis of 5-HTTLPR on depression was inconclusive on its effect, either alone or in combination with life stress.

A 2003 study proposed that a gene-environment interaction (GxE) may explain why life stress is a predictor for depressive episodes in some individuals, but not in others, depending on an allelic variation of the serotonin-transporter-linked promoter region (5-HTTLPR). This hypothesis was widely-discussed in both the scientific literature and popular media, where it was dubbed the “Orchid gene”, but has conclusively failed to replicate in much larger samples, and the observed effect sizes in earlier work are not consistent with the observed polygenicity of depression.

BDNF

BDNF polymorphisms have also been hypothesized to have a genetic influence, but early findings and research failed to replicate in larger samples, and the effect sizes found by earlier estimates are inconsistent with the observed polygenicity of depression.

SIRT1 and LHPP

A 2015 GWAS study in Han Chinese women positively identified two variants in intronic regions near SIRT1 and LHPP with a genome-wide significant association.

Norepinephrine Transporter Polymorphisms

Attempts to find a correlation between norepinephrine transporter polymorphisms and depression have yielded negative results.

One review identified multiple frequently studied candidate genes. The genes encoding for the 5-HTT and 5-HT2A receptor were inconsistently associated with depression and treatment response. Mixed results were found for brain-derived neurotrophic factor (BDNF) Val66Met polymorphisms. Polymorphisms in the tryptophan hydroxylase gene was found to be tentatively associated with suicidal behaviour. A meta analysis of 182 case controlled genetic studies published in 2008 found Apolipoprotein E verepsilon 2 to be protective, and GNB3 825T, MTHFR 677T, SLC6A4 44bp insertion or deletions, and SLC6A3 40 bpVNTR 9/10 genotype to confer risk.

Circadian Rhythm

Depression may be related to abnormalities in the circadian rhythm, or biological clock.

A well synchronised circadian rhythm is critical for maintaining optimal health. Adverse changes and alterations in the circadian rhythm have been associated various neurological disorders and mood disorders including depression.

Depression may be related to the same brain mechanisms that control the cycles of sleep and wakefulness.

Sleep

Sleep disturbance is the most prominent symptom in depressive patients. Studies about sleep electroencephalograms have shown characteristic changes in depression such as reductions in non-rapid eye movement sleep production, disruptions of sleep continuity and disinhibition of rapid eye movement (REM) sleep. Rapid eye movement (REM) sleep – the stage in which dreaming occurs – may be quick to arrive and intense in depressed people. REM sleep depends on decreased serotonin levels in the brain stem, and is impaired by compounds, such as antidepressants, that increase serotonergic tone in brain stem structures. Overall, the serotonergic system is least active during sleep and most active during wakefulness. Prolonged wakefulness due to sleep deprivation activates serotonergic neurons, leading to processes similar to the therapeutic effect of antidepressants, such as the selective serotonin reuptake inhibitors (SSRIs). Depressed individuals can exhibit a significant lift in mood after a night of sleep deprivation. SSRIs may directly depend on the increase of central serotonergic neurotransmission for their therapeutic effect, the same system that impacts cycles of sleep and wakefulness.

Light Therapy

Research on the effects of light therapy on seasonal affective disorder suggests that light deprivation is related to decreased activity in the serotonergic system and to abnormalities in the sleep cycle, particularly insomnia. Exposure to light also targets the serotonergic system, providing more support for the important role this system may play in depression. Sleep deprivation and light therapy both target the same brain neurotransmitter system and brain areas as antidepressant drugs, and are now used clinically to treat depression. Light therapy, sleep deprivation and sleep time displacement (sleep phase advance therapy) are being used in combination quickly to interrupt a deep depression in people who are hospitalised for MDD.

Increased and decreased sleep length appears to be a risk factor for depression. People with MDD sometimes show diurnal and seasonal variation of symptom severity, even in non-seasonal depression. Diurnal mood improvement was associated with activity of dorsal neural networks. Increased mean core temperature was also observed. One hypothesis proposed that depression was a result of a phase shift.

Daytime light exposure correlates with decreased serotonin transporter activity, which may underlie the seasonality of some depression.

Monoamines

Monoamines are neurotransmitters that include serotonin, dopamine, norepinephrine, and epinephrine.

Illustration of the major elements in a prototypical synapse. Synapses are gaps between nerve cells. These cells convert their electrical impulses into bursts of chemical relayers, called neurotransmitters, which travel across the synapses to receptors on adjacent cells, triggering electrical impulses to travel down the latter cells.

Monoamine Hypothesis of Depression

Many antidepressant drugs acutely increase synaptic levels of the monoamine neurotransmitter, serotonin, but they may also enhance the levels of norepinephrine and dopamine. The observation of this efficacy led to the monoamine hypothesis of depression, which postulates that the deficit of certain neurotransmitters is responsible for depression, and even that certain neurotransmitters are linked to specific symptoms. Normal serotonin levels have been linked to mood and behaviour regulation, sleep, and digestion; norepinephrine to the fight-or-flight response; and dopamine to movement, pleasure, and motivation. Some have also proposed the relationship between monoamines and phenotypes such as serotonin in sleep and suicide, norepinephrine in dysphoria, fatigue, apathy, cognitive dysfunction, and dopamine in loss of motivation and psychomotor symptoms.[31] The main limitation for the monoamine hypothesis of depression is the therapeutic lag between initiation of antidepressant treatment and perceived improvement of symptoms. One explanation for this therapeutic lag is that the initial increase in synaptic serotonin is only temporary, as firing of serotonergic neurons in the dorsal raphe adapt via the activity of 5-HT1A autoreceptors. The therapeutic effect of antidepressants is thought to arise from autoreceptor desensitization over a period of time, eventually elevating firing of serotonergic neurons.

Serotonin

Initial studies of serotonin in depression examined peripheral measures such as the serotonin metabolite 5-Hydroxyindoleacetic acid (5-HIAA) and platelet binding. The results were generally inconsistent, and may not generalise to the central nervous system. However evidence from receptor binding studies and pharmacological challenges provide some evidence for dysfunction of serotonin neurotransmission in depression. Serotonin may indirectly influence mood by altering emotional processing biases that are seen at both the cognitive/behavioural and neural level. Pharmacologically reducing serotonin synthesis, and pharmacologically enhancing synaptic serotonin can produce and attenuate negative affective biases, respectively. These emotional processing biases may explain the therapeutic gap.

Dopamine

While various abnormalities have been observed in dopaminergic systems, results have been inconsistent. People with MDD have an increased reward response to dextroamphetamine compared to controls, and it has been suggested that this results from hypersensitivity of dopaminergic pathways due to natural hypoactivity. While polymorphisms of the D4 and D3 receptor have been implicated in depression, associations have not been consistently replicated. Similar inconsistency has been found in post-mortem studies, but various dopamine receptor agonists show promise in treating MDD. There is some evidence that there is decreased nigrostriatal pathway activity in people with melancholic depression (psychomotor retardation). Further supporting the role of dopamine in depression is the consistent finding of decreased cerebrospinal fluid and jugular metabolites of dopamine, as well as post mortem findings of altered Dopamine receptor D3 and dopamine transporter expression. Studies in rodents have supported a potential mechanism involving stress-induced dysfunction of dopaminergic systems.

Monoamine receptors affect phospholipase C and adenylyl cyclase inside of the cell. Green arrows means stimulation and red arrows inhibition. Serotonin receptors are blue, norepinephrine orange, and dopamine yellow. Phospholipase C and adenylyl cyclase start a signalling cascade which turn on or off genes in the cell. Sufficient ATP from mitochondria is required for these downstream signalling events. The 5HT-3 receptor is associated with gastrointestinal adverse effects and has no relationship to the other monoamine receptors.

Catecholamines

A number of lines of evidence indicative of decreased adrenergic activity in depression have been reported. Findings include the decreased activity of tyrosine hydroxylase, decreased size of the locus coeruleus, increased alpha 2 adrenergic receptor density, and decreased alpha 1 adrenergic receptor density. Furthermore, norepinephrine transporter knockout in mice models increases their tolerance to stress, implicating norepinephrine in depression.

One method used to study the role of monoamines is monoamine depletion. Depletion of tryptophan (the precursor of serotonin), tyrosine and phenylalanine (precursors to dopamine) does result in decreased mood in those with a predisposition to depression, but not in persons lacking the predisposition. On the other hand, inhibition of dopamine and norepinephrine synthesis with alpha-methyl-para-tyrosine does not consistently result in decreased mood.

Monoamine Oxidase

An offshoot of the monoamine hypothesis suggests that monoamine oxidase A (MAO-A), an enzyme which metabolises monoamines, may be overly active in depressed people. This would, in turn, cause the lowered levels of monoamines. This hypothesis received support from a PET study, which found significantly elevated activity of MAO-A in the brain of some depressed people. In genetic studies, the alterations of MAO-A-related genes have not been consistently associated with depression. Contrary to the assumptions of the monoamine hypothesis, lowered but not heightened activity of MAO-A was associated with depressive symptoms in adolescents. This association was observed only in maltreated youth, indicating that both biological (MAO genes) and psychological (maltreatment) factors are important in the development of depressive disorders. In addition, some evidence indicates that disrupted information processing within neural networks, rather than changes in chemical balance, might underlie depression.

Limitations

Since the 1990s, research has uncovered multiple limitations of the monoamine hypothesis, and its inadequacy has been criticised within the psychiatric community. For one thing, serotonin system dysfunction cannot be the sole cause of depression. Not all patients treated with antidepressants show improvements despite the usually rapid increase in synaptic serotonin. If significant mood improvements do occur, this is often not for at least two to four weeks. One possible explanation for this lag is that the neurotransmitter activity enhancement is the result of auto receptor desensitization, which can take weeks. Intensive investigation has failed to find convincing evidence of a primary dysfunction of a specific monoamine system in people with MDD. The antidepressants that do not act through the monoamine system, such as tianeptine and opipramol, have been known for a long time. There have also been inconsistent findings with regard to levels of serum 5-HIAA, a metabolite of serotonin. Experiments with pharmacological agents that cause depletion of monoamines have shown that this depletion does not cause depression in healthy people. Another problem that presents is that drugs that deplete monoamines may actually have antidepressant properties. Further, some have argued that depression may be marked by a hyperserotonergic state. Already limited, the monoamine hypothesis has been further oversimplified when presented to the general public.

Receptor Binding

As of 2012, efforts to determine differences in neurotransmitter receptor expression or for function in the brains of people with MDD using positron emission tomography (PET) had shown inconsistent results. Using the PET imaging technology and reagents available as of 2012, it appeared that the D1 receptor may be under-expressed in the striatum of people with MDD. 5-HT1A receptor binding literature is inconsistent; however, it leans towards a general decrease in the mesiotemporal cortex. 5-HT2A receptor binding appears to be unregulated in people with MDD. Results from studies on 5-HTT binding are variable, but tend to indicate higher levels in people with MDD. Results with D2/D3 receptor binding studies are too inconsistent to draw any conclusions. Evidence supports increased MAO activity in people with MDD, and it may even be a trait marker (not changed by response to treatment). Muscarinic receptor binding appears to be increased in depression, and, given ligand binding dynamics, suggests increased cholinergic activity.

Four meta analyses on receptor binding in depression have been performed, two on serotonin transporter (5-HTT), one on 5-HT1A, and another on dopamine transporter (DAT). One meta analysis on 5-HTT reported that binding was reduced in the midbrain and amygdala, with the former correlating with greater age, and the latter correlating with depression severity. Another meta-analysis on 5-HTT including both post-mortem and in vivo receptor binding studies reported that while in vivo studies found reduced 5-HTT in the striatum, amygdala and midbrain, post mortem studies found no significant associations. 5-HT1A was found to be reduced in the anterior cingulate cortex, mesiotemporal lobe, insula, and hippocampus, but not in the amygdala or occipital lobe. The most commonly used 5-HT1A ligands are not displaced by endogenous serotonin, indicating that receptor density or affinity is reduced. Dopamine transporter binding is not changed in depression.

Emotional Processing and Neural Circuits

Emotional Bias

People with MDD show a number of biases in emotional processing, such as a tendency to rate happy faces more negatively, and a tendency to allocate more attentional resources to sad expressions. Depressed people also have impaired recognition of happy, angry, disgusted, fearful and surprised, but not sad faces. Functional neuroimaging has demonstrated hyperactivity of various brain regions in response to negative emotional stimuli, and hypoactivity in response to positive stimuli. One meta analysis reported that depressed subjects showed decreased activity in the left dorsolateral prefrontal cortex and increased activity in the amygdala in response to negative stimuli. Another meta analysis reported elevated hippocampus and thalamus activity in a subgroup of depressed subjects who were medication naïve, not elderly, and had no comorbidities. The therapeutic lag of antidepressants has been suggested to be a result of antidepressants modifying emotional processing leading to mood changes. This is supported by the observation that both acute and sub-chronic SSRI administration increases response to positive faces. Antidepressant treatment appears to reverse mood congruent biases in limbic, prefrontal, and fusiform areas. dlPFC response is enhanced and amygdala response is attenuated during processing of negative emotions, the former or which is thought to reflect increased top down regulation. The fusiform gyrus and other visual processing areas respond more strongly to positive stimuli with antidepressant treatment, which is thought to reflect the a positive processing bias. These effects do not appear to be unique to serotonergic or noradrenergic antidepressants, but also occur in other forms of treatment such as deep brain stimulation.

Neural Circuits

One meta analysis of functional neuroimaging in depression observed a pattern of abnormal neural activity hypothesized to reflect an emotional processing bias. Relative to controls, people with MDD showed hyperactivity of circuits in the salience network (SN), composed of the pulvinar nuclei, the insula, and the dorsal anterior cingulate cortex (dACC), as well as decreased activity in regulatory circuits composed of the striatum and dlPFC.

A neuroanatomical model called the limbic-cortical model has been proposed to explain early biological findings in depression. The model attempts to relate specific symptoms of depression to neurological abnormalities. Elevated resting amygdala activity was proposed to underlie rumination, as stimulation of the amygdala has been reported to be associated with the intrusive recall of negative memories. The ACC was divided into pregenual (pgACC) and subgenual regions (sgACC), with the former being electrophysiologically associated with fear, and the latter being metabolically implicated in sadness in healthy subjects. Hyperactivity of the lateral orbitofrontal and insular regions, along with abnormalities in lateral prefrontal regions was suggested to underlie maladaptive emotional responses, given the regions roles in reward learning. This model and another termed “the cortical striatal model”, which focused more on abnormalities in the cortico-basal ganglia-thalamo-cortical loop, have been supported by recent literature. Reduced striatal activity, elevated OFC activity, and elevated sgACC activity were all findings consistent with the proposed models. However, amygdala activity was reported to be decreased, contrary to the limbic-cortical model. Furthermore, only lateral prefrontal regions were modulated by treatment, indicating that prefrontal areas are state markers (i.e. dependent upon mood), while subcortical abnormalities are trait markers (i.e. reflect a susceptibility).

Reward

While depression severity as a whole is not correlated with a blunted neural response to reward, anhedonia is directly correlated to reduced activity in the reward system. The study of reward in depression is limited by heterogeneity in the definition and conceptualisations of reward and anhedonia. Anhedonia is broadly defined as a reduced ability to feel pleasure, but questionnaires and clinical assessments rarely distinguish between motivational “wanting” and consummatory “liking”. While a number of studies suggest that depressed subjects rate positive stimuli less positively and as less arousing, a number of studies fail to find a difference. Furthermore, response to natural rewards such as sucrose does not appear to be attenuated. General affective blunting may explain “anhedonic” symptoms in depression, as meta analysis of both positive and negative stimuli reveal reduced rating of intensity. As anhedonia is a prominent symptom of depression, direct comparison of depressed with healthy subjects reveals increased activation of the subgenual anterior cingulate cortex (sgACC), and reduced activation of the ventral striatum, and in particular the nucleus accumbens (NAcc) in response to positive stimuli. Although the finding of reduced NAcc activity during reward paradigms is fairly consistent, the NAcc is made up of a functionally diverse range of neurons, and reduced blood-oxygen-level dependent (BOLD) signal in this region could indicate a variety of things including reduced afferent activity or reduced inhibitory output. Nevertheless, these regions are important in reward processing, and dysfunction of them in depression is thought to underlie anhedonia. Residual anhedonia that is not well targeted by serotonergic antidepressants is hypothesized to result from inhibition of dopamine release by activation of 5-HT2C receptors in the striatum. The response to reward in the medial orbitofrontal cortex (OFC) is attenuated in depression, while lateral OFC response is enhanced to punishment. The lateral OFC shows sustained response to absence of reward or punishment, and it is thought to be necessary for modifying behaviour in response to changing contingencies. Hypersensitivity in the lOFC may lead to depression by producing a similar effect to learned helplessness in animals.

Elevated response in the sgACC is a consistent finding in neuroimaging studies using a number of paradigms including reward related tasks. Treatment is also associated with attenuated activity in the sgACC, and inhibition of neurons in the rodent homologue of the sgACC, the infralimbic cortex (IL), produces an antidepressant effect. Hyperactivity of the sgACC has been hypothesized to lead to depression via attenuating the somatic response to reward or positive stimuli. Contrary to studies of functional magnetic resonance imaging response in the sgACC during tasks, resting metabolism is reduced in the sgACC. However, this is only apparent when correcting for the prominent reduction in sgACC volume associated with depression; structural abnormalities are evident at a cellular level, as neuropathological studies report reduced sgACC cell markers. The model of depression proposed from these findings by Drevets et al. suggests that reduced sgACC activity results in enhanced sympathetic nervous system activity and blunted HPA axis feedback. Activity in the sgACC may also not be causal in depression, as the authors of one review that examined neuroimaging in depressed subjects during emotional regulation hypothesized that the pattern of elevated sgACC activity reflected increased need to modulate automatic emotional responses in depression. More extensive sgACC and general prefrontal recruitment during positive emotional processing was associated with blunted subcortical response to positive emotions, and subject anhedonia. This was interpreted by the authors to reflect a downregulation of positive emotions by the excessive recruitment of the prefrontal cortex.

Neuroanatomy

While a number of neuroimaging findings are consistently reported in people with major depressive disorder, the heterogeneity of depressed populations presents difficulties interpreting these findings. For example, averaging across populations may hide certain subgroup related findings; while reduced dlPFC activity is reported in depression, a subgroup may present with elevated dlPFC activity. Averaging may also yield statistically significant findings, such as reduced hippocampal volumes, that are actually present in a subgroup of subjects. Due to these issues and others, including the longitudinal consistency of depression, most neural models are likely inapplicable to all depression.

Structural Neuroimaging

Meta analyses performed using seed-based d mapping have reported grey matter reductions in a number of frontal regions. One meta analysis of early onset general depression reported grey matter reductions in the bilateral anterior cingulate cortex (ACC) and dorsomedial prefrontal cortex (dmPFC). One meta analysis on first episode depression observed distinct patterns of grey matter reductions in medication free, and combined populations; medication free depression was associated with reductions in the right dorsolateral prefrontal cortex, right amygdala, and right inferior temporal gyrus; analysis on a combination of medication free and medicated depression found reductions in the left insula, right supplementary motor area, and right middle temporal gyrus. Another review distinguishing medicated and medication free populations, albeit not restricted to people with their first episode of MDD, found reductions in the combined population in the bilateral superior, right middle, and left inferior frontal gyrus, along with the bilateral parahippocampus. Increases in thalamic and ACC grey matter was reported in the medication free and medicated populations respectively. A meta analysis performed using “activation likelihood estimate” reported reductions in the paracingulate cortex, dACC and amygdala.

GMV reductions in MDD and BD.

Using statistical parametric mapping, one meta analysis replicated previous findings of reduced grey matter in the ACC, medial prefrontal cortex, inferior frontal gyrus, hippocampus and thalamus; however reductions in the OFC and ventromedial prefrontal cortex grey matter were also reported.

Two studies on depression from the ENIGMA consortium have been published, one on cortical thickness, and the other on subcortical volume. Reduced cortical thickness was reported in the bilateral OFC, ACC, insula, middle temporal gyri, fusiform gyri, and posterior cingulate cortices, while surface area deficits were found in medial occipital, inferior parietal, orbitofrontal and precentral regions. Subcortical abnormalities, including reductions in hippocampus and amygdala volumes, which were especially pronounced in early onset depression.

Multiple meta analysis have been performed on studies assessing white matter integrity using fractional anisotropy (FA). Reduced FA has been reported in the corpus callosum (CC) in both first episode medication naïve, and general major depressive populations. The extent of CC reductions differs from study to study. People with MDD who have not taken antidepressants before have been reported to have reductions only in the body of the CC and only in the genu of the CC. On the other hand, general MDD samples have been reported to have reductions in the body of the CC, the body and genu of the CC, and only the genu of the CC. Reductions of FA have also been reported in the anterior limb of the internal capsule (ALIC) and superior longitudinal fasciculus.

Functional Neuroimaging

Studies of resting state activity have utilised a number of indicators of resting state activity, including regional homogeneity (ReHO), amplitude of low frequency fluctuations (ALFF), fractional amplitude of low frequency fluctuations (fALFF), arterial spin labelling (ASL), and positron emission tomography measures of regional cerebral blood flow or metabolism.

MDD is associated with reduced FA in the ALIC and genu/body of the CC.

Studies using ALFF and fALFF have reported elevations in ACC activity, with the former primarily reporting more ventral findings, and the latter more dorsal findings. A conjunction analysis of ALFF and CBF studies converged on the left insula, with previously untreated people having increased insula activity. Elevated caudate CBF was also reported A meta analysis combining multiple indicators of resting activity reported elevated anterior cingulate, striatal, and thalamic activity and reduced left insula, post-central gyrus and fusiform gyrus activity. An activation likelihood estimate (ALE) meta analysis of PET/SPECT resting state studies reported reduced activity in the left insula, pregenual and dorsal anterior cingulate cortex and elevated activity in the thalamus, caudate, anterior hippocampus and amygdala. Compared to the ALE meta analysis of PET/SPECT studies, a study using multi-kernel density analysis reported hyperactivity only in the pulvinar nuclei of the thalamus.

Brain Regions

Research on the brains of people with MDD usually shows disturbed patterns of interaction between multiple parts of the brain. Several areas of the brain are implicated in studies seeking to more fully understand the biology of depression:

Subgenual Cingulate

Studies have shown that Brodmann area 25, also known as subgenual cingulate, is metabolically overactive in treatment-resistant depression. This region is extremely rich in serotonin transporters and is considered as a governor for a vast network involving areas like hypothalamus and brain stem, which influences changes in appetite and sleep; the amygdala and insula, which affect the mood and anxiety; the hippocampus, which plays an important role in memory formation; and some parts of the frontal cortex responsible for self-esteem. Thus disturbances in this area or a smaller than normal size of this area contributes to depression. Deep brain stimulation has been targeted to this region in order to reduce its activity in people with treatment resistant depression.

Prefrontal Cortex

One review reported hypoactivity in the prefrontal cortex of those with depression compared to controls. The prefrontal cortex is involved in emotional processing and regulation, and dysfunction of this process may be involved in the aetiology of depression. One study on antidepressant treatment found an increase in PFC activity in response to administration of antidepressants. One meta analysis published in 2012 found that areas of the prefrontal cortex were hypoactive in response to negative stimuli in people with MDD. One study suggested that areas of the prefrontal cortex are part of a network of regions including dorsal and pregenual cingulate, bilateral middle frontal gyrus, insula and superior temporal gyrus that appear to be hypoactive in people with MDD. However the authors cautioned that the exclusion criteria, lack of consistency and small samples limit results.

Amygdala

The amygdala, a structure involved in emotional processing appears to be hyperactive in those with major depressive disorder. The amygdala in unmedicated depressed persons tended to be smaller than in those that were medicated, however aggregate data shows no difference between depressed and healthy persons. During emotional processing tasks right amygdala is more active than the left, however there is no differences during cognitive tasks, and at rest only the left amygdala appears to be more hyperactive. One study, however, found no difference in amygdala activity during emotional processing tasks.

Hippocampus

Atrophy of the hippocampus has been observed during depression, consistent with animal models of stress and neurogenesis.

Stress can cause depression and depression-like symptoms through monoaminergic changes in several key brain regions as well as suppression in hippocampal neurogenesis. This leads to alteration in emotion and cognition related brain regions as well as HPA axis dysfunction. Through the dysfunction, the effects of stress can be exacerbated including its effects on 5-HT. Furthermore, some of these effects are reversed by antidepressant action, which may act by increasing hippocampal neurogenesis. This leads to a restoration in HPA activity and stress reactivity, thus restoring the deleterious effects induced by stress on 5-HT.

The hypothalamic-pituitary-adrenal axis is a chain of endocrine structures that are activated during the body’s response to stressors of various sorts. The HPA axis involves three structure, the hypothalamus which release CRH that stimulates the pituitary gland to release ACTH which stimulates the adrenal glands to release cortisol. Cortisol has a negative feedback effect on the pituitary gland and hypothalamus. In people with MDD this often shows increased activation in depressed people, but the mechanism behind this is not yet known. Increased basal cortisol levels and abnormal response to dexamethasone challenges have been observed in people with MDD. Early life stress has been hypothesized as a potential cause of HPA dysfunction. HPA axis regulation may be examined through a dexamethasone suppression tests, which tests the feedback mechanisms. Non-suppression of dexamethasone is a common finding in depression, but is not consistent enough to be used as a diagnostic tool. HPA axis changes may be responsible for some of the changes such as decreased bone mineral density and increased weight found in people with MDD. One drug, ketoconazole, currently under development has shown promise in treating MDD.

Hippocampal Neurogenesis

Reduced hippocampal neurogenesis leads to a reduction in hippocampal volume. A genetically smaller hippocampus has been linked to a reduced ability to process psychological trauma and external stress, and subsequent predisposition to psychological illness. Depression without familial risk or childhood trauma has been linked to a normal hippocampal volume but localised dysfunction.

Animal Models

A number of animal models exist for depression, but they are limited in that depression involves primarily subjective emotional changes. However, some of these changes are reflected in physiology and behaviour, the latter of which is the target of many animal models. These models are generally assessed according to four facets of validity; the reflection of the core symptoms in the model; the predictive validity of the model; the validity of the model with regard to human characteristics of aetiology; and the biological plausibility.

Different models for inducing depressive behaviours have been utilised; neuroanatomical manipulations such as olfactory bulbectomy or circuit specific manipulations with optogenetics; genetic models such as 5-HT1A knockout or selectively bred animals; models involving environmental manipulation associated with depression in humans, including chronic mild stress, early life stress and learned helplessness. The validity of these models in producing depressive behaviours may be assessed with a number of behavioural tests. Anhedonia and motivational deficits may, for example, be assessed via examining an animal’s level of engagement with rewarding stimuli such as sucrose or intracranial self-stimulation. Anxious and irritable symptoms may be assessed with exploratory behaviour in the presence of a stressful or novelty environment, such as the open field test, novelty suppressed feeding, or the elevated plus-maze. Fatigue, psychomotor poverty, and agitation may be assessed with locomotor activity, grooming activity, and open field tests.

Animal models possess a number of limitations due to the nature of depression. Some core symptoms of depression, such as rumination, low self-esteem, guilt, and depressed mood cannot be assessed in animals as they require subjective reporting. From an evolutionary standpoint, the behaviour correlates of defeats of loss are thought to be an adaptive response to prevent further loss. Therefore, attempts to model depression that seeks to induce defeat or despair may actually reflect adaption and not disease. Furthermore, while depression and anxiety are frequently comorbid, dissociation of the two in animal models is difficult to achieve. Pharmacological assessment of validity is frequently disconnected from clinical pharmacotherapeutics in that most screening tests assess acute effects, while antidepressants normally take a few weeks to work in humans.

Neurocircuits

Regions involved in reward are common targets of manipulation in animal models of depression, including the nucleus accumbens (NAc), ventral tegmental area (VTA), ventral pallidum (VP), lateral habenula (LHb) and medial prefrontal cortex (mPFC). Tentative fMRI studies in humans demonstrate elevated LHb activity in depression. The lateral habenula projects to the RMTg to drive inhibition of dopamine neurons in the VTA during omission of reward. In animal models of depression, elevated activity has been reported in LHb neurons that project to the ventral tegmental area (ostensibly reducing dopamine release). The LHb also projects to aversion reactive mPFC neurons, which may provide an indirect mechanism for producing depressive behaviours. Learned helplessness induced potentiation of LHb synapses are reversed by antidepressant treatment, providing predictive validity. A number of inputs to the LHb have been implicated in producing depressive behaviours. Silencing GABAergic projections from the NAc to the LHb reduces conditioned place preference induced in social aggression, and activation of these terminals induces CPP. Ventral pallidum firing is also elevated by stress induced depression, an effect that is pharmacologically valid, and silencing of these neurons alleviates behavioural correlates of depression. Tentative in vivo evidence from people with MDD suggests abnormalities in dopamine signalling. This led to early studies investigating VTA activity and manipulations in animal models of depression. Massive destruction of VTA neurons enhances depressive behaviours, while VTA neurons reduce firing in response to chronic stress. However, more recent specific manipulations of the VTA produce varying results, with the specific animal model, duration of VTA manipulation, method of VTA manipulation, and subregion of VTA manipulation all potentially leading to differential outcomes. Stress and social defeat induced depressive symptoms, including anhedonia, are associated with potentiation of excitatory inputs to Dopamine D2 receptor-expressing medium spiny neurons (D2-MSNs) and depression of excitatory inputs to Dopamine D1 receptor-expressing medium spiny neurons (D1-MSNs). Optogenetic excitation of D1-MSNs alleviates depressive symptoms and is rewarding, while the same with D2-MSNs enhances depressive symptoms. Excitation of glutaminergic inputs from the ventral hippocampus reduces social interactions, and enhancing these projections produces susceptibility to stress-induced depression. Manipulations of different regions of the mPFC can produce and attenuate depressive behaviours. For example, inhibiting mPFC neurons specifically in the intralimbic cortex attenuates depressive behaviours. The conflicting findings associated with mPFC stimulation, when compared to the relatively specific findings in the infralimbic cortex, suggest that the prelimbic cortex and infralimbic cortex may mediate opposing effects. mPFC projections to the raphe nuclei are largely GABAergic and inhibit the firing of serotonergic neurons. Specific activation of these regions reduce immobility in the forced swim test but do not affect open field or forced swim behaviour. Inhibition of the raphe shifts the behavioural phenotype of uncontrolled stress to a phenotype closer to that of controlled stress.

Altered Neuroplasticity

Recent studies have called attention to the role of altered neuroplasticity in depression. A review found a convergence of three phenomena:

  • Chronic stress reduces synaptic and dendritic plasticity;
  • Depressed subjects show evidence of impaired neuroplasticity (e.g. shortening and reduced complexity of dendritic trees); and
  • Anti-depressant medications may enhance neuroplasticity at both a molecular and dendritic level.

The conclusion is that disrupted neuroplasticity is an underlying feature of depression, and is reversed by antidepressants.

Blood levels of BDNF in people with MDD increase significantly with antidepressant treatment and correlate with decrease in symptoms. Post mortem studies and rat models demonstrate decreased neuronal density in the prefrontal cortex thickness in people with MDD. Rat models demonstrate histological changes consistent with MRI findings in humans, however studies on neurogenesis in humans are limited. Antidepressants appear to reverse the changes in neurogenesis in both animal models and humans.

Inflammation

Various reviews have found that general inflammation may play a role in depression. One meta analysis of cytokines in people with MDD found increased levels of pro-inflammatory IL-6 and TNF-a levels relative to controls. The first theories came about when it was noticed that interferon therapy caused depression in a large number of people receiving it. Meta analysis on cytokine levels in people with MDD have demonstrated increased levels of IL-1, IL-6, C-reactive protein, but not IL-10. Increased numbers of T-Cells presenting activation markers, levels of neopterin, IFN gamma, sTNFR, and IL-2 receptors have been observed in depression. Various sources of inflammation in depressive illness have been hypothesized and include trauma, sleep problems, diet, smoking and obesity. Cytokines, by manipulating neurotransmitters, are involved in the generation of sickness behaviour, which shares some overlap with the symptoms of depression. Neurotransmitters hypothesized to be affected include dopamine and serotonin, which are common targets for antidepressant drugs. Induction of indolamine-2,3 dioxygenease by cytokines has been proposed as a mechanism by which immune dysfunction causes depression. One review found normalization of cytokine levels after successful treatment of depression. A meta analysis published in 2014 found the use of anti-inflammatory drugs such as NSAIDs and investigational cytokine inhibitors reduced depressive symptoms. Exercise can act as a stressor, decreasing the levels of IL-6 and TNF-a and increasing those of IL-10, an anti-inflammatory cytokine.

Inflammation is also intimately linked with metabolic processes in humans. For example, low levels of Vitamin D have been associated with greater risk for depression. The role of metabolic biomarkers in depression is an active research area. Recent work has explored the potential relationship between plasma sterols and depressive symptom severity.

Oxidative Stress

A marker of DNA oxidation, 8-Oxo-2′-deoxyguanosine, has been found to be increased in both the plasma and urine of people with MDD. This along with the finding of increased F2-isoprostanes levels found in blood, urine and cerebrospinal fluid indicate increased damage to lipids and DNA in people with MDD. Studies with 8-Oxo-2′ Deoxyguanosine varied by methods of measurement and type of depression, but F2-Isoprostane level was consistent across depression types. Authors suggested lifestyle factors, dysregulation of the HPA axis, immune system and autonomics nervous system as possible causes. Another meta-analysis found similar results with regards to oxidative damage products as well as decreased oxidative capacity. Oxidative DNA damage may play a role in MDD.

Mitochondrial Dysfunction:

Increased markers of oxidative stress relative to controls have been found in people with MDD. These markers include high levels of RNS and ROS which have been shown to influence chronic inflammation, damaging the electron transport chain and biochemical cascades in mitochondria. This lowers the activity of enzymes in the respiratory chain resulting in mitochondrial dysfunction. The brain is a highly energy-consuming and has little capacity to store glucose as glycogen and so depends greatly on mitochondria. Mitochondrial dysfunction has been linked to the dampened neuroplasticity observed in depressed brains.

Large-Scale Brain Network Theory

Instead of studying one brain region, studying large scale brain networks is another approach to understanding psychiatric and neurological disorders, supported by recent research that has shown that multiple brain regions are involved in these disorders. Understanding the disruptions in these networks may provide important insights into interventions for treating these disorders. Recent work suggests that at least three large-scale brain networks are important in psychopathology.

Central Executive Network

The central executive network is made up of fronto-parietal regions, including dorsolateral prefrontal cortex and lateral posterior parietal cortex. This network is involved in high level cognitive functions such as maintaining and using information in working memory, problem solving, and decision making. Deficiencies in this network are common in most major psychiatric and neurological disorders, including depression. Because this network is crucial for everyday life activities, those who are depressed can show impairment in basic activities like test taking and being decisive.

Default Mode Network

The default mode network includes hubs in the prefrontal cortex and posterior cingulate, with other prominent regions of the network in the medial temporal lobe and angular gyrus. The default mode network is usually active during mind-wandering and thinking about social situations. In contrast, during specific tasks probed in cognitive science (for example, simple attention tasks), the default network is often deactivated. Research has shown that regions in the default mode network (including medial prefrontal cortex and posterior cingulate) show greater activity when depressed participants ruminate (that is, when they engage in repetitive self-focused thinking) than when typical, healthy participants ruminate. People with MDD also show increased connectivity between the default mode network and the subgenual cingulate and the adjoining ventromedial prefrontal cortex in comparison to healthy individuals, individuals with dementia or with autism. Numerous studies suggest that the subgenual cingulate plays an important role in the dysfunction that characterizes major depression. The increased activation in the default mode network during rumination and the atypical connectivity between core default mode regions and the subgenual cingulate may underlie the tendency for depressed individual to get “stuck” in the negative, self-focused thoughts that often characterise depression. However, further research is needed to gain a precise understanding of how these network interactions map to specific symptoms of depression.

Salience Network

The salience network is a cingulate-frontal operculum network that includes core nodes in the anterior cingulate and anterior insula. A salience network is a large-scale brain network involved in detecting and orienting the most pertinent of the external stimuli and internal events being presented. Individuals who have a tendency to experience negative emotional states (scoring high on measures of neuroticism) show an increase in the right anterior insula during decision-making, even if the decision has already been made. This atypically high activity in the right anterior insula is thought to contribute to the experience of negative and worrisome feelings. In MDD, anxiety is often a part of the emotional state that characterises depression.

What is Physical Dependence?

Introduction

Physical dependence is a physical condition caused by chronic use of a tolerance-forming drug, in which abrupt or gradual drug withdrawal causes unpleasant physical symptoms.

Physical dependence can develop from low-dose therapeutic use of certain medications such as benzodiazepines, opioids, antiepileptics and antidepressants, as well as the recreational misuse of drugs such as alcohol, opioids and benzodiazepines. The higher the dose used, the greater the duration of use, and the earlier age use began are predictive of worsened physical dependence and thus more severe withdrawal syndromes.

Acute withdrawal syndromes can last days, weeks or months. Protracted withdrawal syndrome, also known as post-acute-withdrawal syndrome or “PAWS”, is a low-grade continuation of some of the symptoms of acute withdrawal, typically in a remitting-relapsing pattern, often resulting in relapse and prolonged disability of a degree to preclude the possibility of lawful employment. Protracted withdrawal syndrome can last for months, years, or depending on individual factors, indefinitely. Protracted withdrawal syndrome is noted to be most often caused by benzodiazepines. To dispel the popular mis-association with addiction, physical dependence to medications is sometimes compared to dependence on insulin by persons with diabetes.

Symptoms

Physical dependence can manifest itself in the appearance of both physical and psychological symptoms which are caused by physiological adaptions in the central nervous system and the brain due to chronic exposure to a substance. Symptoms which may be experienced during withdrawal or reduction in dosage include increased heart rate and/or blood pressure, sweating, and tremors.[9] More serious withdrawal symptoms such as confusion, seizures, and visual hallucinations indicate a serious emergency and the need for immediate medical care.

Sedative hypnotic drugs such as alcohol, benzodiazepines, and barbiturates are the only commonly available substances that can be fatal in withdrawal due to their propensity to induce withdrawal convulsions. Abrupt withdrawal from other drugs, such as opioids can cause an extremely painful withdrawal that is very rarely fatal in patients of general good health and with medical treatment, but is more often fatal in patients with weakened cardiovascular systems; toxicity is generally caused by the often-extreme increases in heart rate and blood pressure (which can be treated with clonidine), or due to arrhythmia due to electrolyte imbalance caused by the inability to eat, and constant diarrhoea and vomiting (which can be treated with loperamide and ondansetron respectively) associated with acute opioid withdrawal, especially in longer-acting substances where the diarrhoea and emesis can continue unabated for weeks, although life-threatening complications are extremely rare, and nearly non-existent with proper medical management.

Treatment

Treatment for physical dependence depends upon the drug being withdrawn and often includes administration of another drug, especially for substances that can be dangerous when abruptly discontinued or when previous attempts have failed. Physical dependence is usually managed by a slow dose reduction over a period of weeks, months or sometimes longer depending on the drug, dose and the individual. A physical dependence on alcohol is often managed with a cross tolerant drug, such as long acting benzodiazepines to manage the alcohol withdrawal symptoms.

Drugs That Cause Physical Dependence

  • All µ-opioids with any (even slight) agonist effect, such as (partial list) morphine, heroin, codeine, oxycodone, buprenorphine, nalbuphine, methadone, and fentanyl, but not agonists specific to non-µ opioid receptors, such as salvinorin A (a k-opioid agonist), nor opioid antagonists or inverse agonists, such as naltrexone (a universal opioid inverse agonist).
  • All GABA agonists and positive allosteric modulators of both the GABA-A ionotropic receptor and GABA-B metabotropic receptor subunits, including (partial list):
  • Nicotine (tobacco) (cf. nicotine withdrawal).
  • Gabapentinoids such as gabapentin (Neurontin), pregabalin (Lyrica), and phenibut (Noofen), which are inhibitors of α2δ subunit-containing VDCCs.
  • Antiepileptic drugs such as valproate, lamotrigine, tiagabine, vigabatrin, carbamazepine and oxcarbazepine, and topiramate.
  • Antipsychotic drugs such as clozapine, risperidone, olanzapine, haloperidol, thioridazine, etc.
  • Commonly prescribed antidepressants such as the selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) (cf. SSRI/SNRI withdrawal syndrome).
  • Blood pressure medications, including beta blockers such as propanolol and alpha-adrenergic agonists such as clonidine.
  • Androgenic-anabolic steroids.
  • Glucocorticoids.

Rebound Syndrome

Refer to Rebound Effect.

A wide range of drugs whilst not causing a true physical dependence can still cause withdrawal symptoms or rebound effects during dosage reduction or especially abrupt or rapid withdrawal. These can include caffeine, stimulants, steroidal drugs and antiparkinsonian drugs. It is debated whether the entire antipsychotic drug class causes true physical dependency, a subset, or if none do. But, if discontinued too rapidly, it could cause an acute withdrawal syndrome. When talking about illicit drugs rebound withdrawal, especially with stimulants, it is sometimes referred to as “coming down” or “crashing”.

Some drugs, like anticonvulsants and antidepressants, describe the drug category and not the mechanism. The individual agents and drug classes in the anticonvulsant drug category act at many different receptors and it is not possible to generalise their potential for physical dependence or incidence or severity of rebound syndrome as a group so they must be looked at individually. Anticonvulsants as a group however are known to cause tolerance to the anti-seizure effect. SSRI drugs, which have an important use as antidepressants, engender a discontinuation syndrome that manifests with physical side effects; e.g. there have been case reports of a discontinuation syndrome with venlafaxine (Effexor).

What is Reduced Effect Display?

Introduction

Reduced affect display, sometimes referred to as emotional blunting, is a condition of reduced emotional reactivity in an individual.

It manifests as a failure to express feelings (affect display) either verbally or nonverbally, especially when talking about issues that would normally be expected to engage the emotions. Expressive gestures are rare and there is little animation in facial expression or vocal inflection. Reduced affect can be symptomatic of autism, schizophrenia, depression, posttraumatic stress disorder, depersonalisation disorder, schizoid personality disorder or brain damage. It may also be a side effect of certain medications (e.g. antipsychotics and antidepressants).

Reduced affect should be distinguished from apathy and anhedonia, which explicitly refer to a lack of emotion, whereas reduced affect is a lack of emotional expression (affect display) regardless of whether emotion (underlying affect) is actually reduced or not.

Types

Constricted Affect

A restricted or constricted affect is a reduction in an individual’s expressive range and the intensity of emotional responses.

Blunted and Flat Affect

Blunted affect is a lack of affect more severe than restricted or constricted affect, but less severe than flat or flattened affect. “The difference between flat and blunted affect is in degree. A person with flat affect has no or nearly no emotional expression. They may not react at all to circumstances that usually evoke strong emotions in others. A person with blunted affect, on the other hand, has a significantly reduced intensity in emotional expression”.

Shallow Affect

Shallow affect has equivalent meaning to blunted affect. Factor 1 of the Psychopathy Checklist identifies shallow affect as a common attribute of psychopathy.

Brain structures

Individuals with schizophrenia with blunted affect show different regional brain activity in fMRI scans when presented with emotional stimuli compared to individuals with schizophrenia without blunted affect. Individuals with schizophrenia without blunted affect show activation in the following brain areas when shown emotionally negative pictures: midbrain, pons, anterior cingulate cortex, insula, ventrolateral orbitofrontal cortex, anterior temporal pole, amygdala, medial prefrontal cortex, and extrastriate visual cortex. Individuals with schizophrenia with blunted affect show activation in the following brain regions when shown emotionally negative pictures: midbrain, pons, anterior temporal pole, and extrastriate visual cortex.

Limbic Structures

Individuals with schizophrenia with flat affect show decreased activation in the limbic system when viewing emotional stimuli. In individuals with schizophrenia with blunted affect neural processes begin in the occipitotemporal region of the brain and go through the ventral visual pathway and the limbic structures until they reach the inferior frontal areas. Damage to the amygdala of adult rhesus macaques early in life can permanently alter affective processing. Lesioning the amygdala causes blunted affect responses to both positive and negative stimuli. This effect is irreversible in the rhesus macaques; neonatal damage produces the same effect as damage that occurs later in life. The macaques’ brain cannot compensate for early amygdala damage even though significant neuronal growth may occur. There is some evidence that blunted affect symptoms in schizophrenia patients are not a result of just amygdala responsiveness, but a result of the amygdala not being integrated with other areas of the brain associated with emotional processing, particularly in amygdala-prefrontal cortex coupling. Damage in the limbic region prevents the amygdala from correctly interpreting emotional stimuli in individuals with schizophrenia by compromising the link between the amygdala and other brain regions associated with emotion.

Brainstem

Parts of the brainstem are responsible for passive emotional coping strategies that are characterised by disengagement or withdrawal from the external environment (quiescence, immobility, hyporeactivity), similar to what is seen in blunted affect. Individuals with schizophrenia with blunted affect show activation of the brainstem during fMRI scans, particularly the right medulla and the left pons, when shown “sad” film excerpts. The bilateral midbrain is also activated in individuals with schizophrenia diagnosed with blunted affect. Activation of the midbrain is thought to be related to autonomic responses associated with perceptual processing of emotional stimuli. This region usually becomes activated in diverse emotional states. When the connectivity between the midbrain and the medial prefrontal cortex is compromised in individuals with schizophrenia with blunted affect an absence of emotional reaction to external stimuli results.

Prefrontal Cortex

Individuals with schizophrenia, as well as patients being successfully reconditioned with quetiapine for blunted affect, show activation of the prefrontal cortex (PFC). Failure to activate the PFC is possibly involved in impaired emotional processing in individuals with schizophrenia with blunted affect. The mesial PFC is activated in aver individuals in response to external emotional stimuli. This structure possibly receives information from the limbic structures to regulate emotional experiences and behaviour. Individuals being reconditioned with quetiapine, who show reduced symptoms, show activation in other areas of the PFC as well, including the right medial prefrontal gyrus and the left orbitofrontal gyrus.

Anterior Cingulate Cortex

A positive correlation has been found between activation of the anterior cingulate cortex and the reported magnitude of sad feelings evoked by viewing sad film excerpts. The rostral subdivision of this region is possibly involved in detecting emotional signals. This region is different in individuals with schizophrenia with blunted affect.

Diagnoses

Schizophrenia

Flat and blunted affect is a defining characteristic in the presentation of schizophrenia. To reiterate, these individuals have a decrease in observed vocal and facial expression as well as the use of gestures. One study of flat affect in schizophrenia found that “flat affect was more common in men, and was associated with worse current quality of life” as well as having “an adverse effect on course of illness”.

The study also reported a “dissociation between reported experience of emotion and its display” – supporting the suggestion made elsewhere that “blunted affect, including flattened facial expressiveness and lack of vocal inflection … often disguises an individual’s true feelings.” Thus, feelings may merely be unexpressed, rather than totally lacking. On the other hand, “a lack of emotions which is due not to mere repression but to a real loss of contact with the objective world gives the observer a specific impression of ‘queerness’ … the remainders of emotions or the substitutes for emotions usually refer to rage and aggressiveness”. In the most extreme cases, there is a complete “dissociation from affective states”. To further support this idea, a study examining emotion dysregulation found that individuals with schizophrenia could not exaggerate their emotional expression as healthy controls could. Participants were asked to express whatever emotions they had during a clip of a film, and the participants with schizophrenia showed deficits in behavioural expression of their emotions.

There is still some debate regarding the source of flat affect in schizophrenia. However, some literature indicates abnormalities in the dorsal executive and ventral affective systems; it is argued that dorsal hypoactivation and ventral hyperactivation may be the source of flat affect. Further, the authors found deficits in the mirror neuron system may also contribute to flat affect in that the deficits may cause disruptions in the control of facial expression.

Another study found that when speaking, individuals with schizophrenia with flat affect demonstrate less inflection than normal controls and appear to be less fluent. Normal subjects appear to express themselves using more complex syntax, whereas flat affect subjects speak with fewer words, and fewer words per sentence. Flat affect individuals’ use of context-appropriate words in both sad and happy narratives are similar to that of controls. It is very likely that flat affect is a result of deficits in motor expression as opposed to emotional processing. The moods of display are compromised, but subjective, autonomic, and contextual aspects of emotion are left intact.

Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) was previously known to cause negative feelings, such as depressed mood, re-experiencing and hyperarousal. However, recently, psychologists have started to focus their attention on the blunted affects and also the decrease in feeling and expressing positive emotions in PTSD patients. Blunted affect, or emotional numbness, is considered one of the consequences of PTSD because it causes a diminished interest in activities that produce pleasure (anhedonia) and produces feelings of detachment from others, restricted emotional expression and a reduced tendency to express emotions behaviourally. Blunted affect is often seen in veterans as a consequence of the psychological stressful experiences that caused PTSD. Blunted affect is a response to PTSD, it is considered one of the central symptoms in post-traumatic stress disorders and it is often seen in veterans who served in combat zones. In PTSD, blunted affect can be considered a psychological response to PTSD as a way to combat overwhelming anxiety that the patients feel. In blunted affect, there are abnormalities in circuits that also include the prefrontal cortex.

Assessment

In making assessments of mood and affect the clinician is cautioned that “it is important to keep in mind that demonstrative expression can be influenced by cultural differences, medication, or situational factors”; while the layperson is warned to beware of applying the criterion lightly to “friends, otherwise [he or she] is likely to make false judgments, in view of the prevalence of schizoid and cyclothymic personalities in our ‘normal’ population, and our [US] tendency to psychological hypochondriasis”.

R.D. Laing in particular stressed that “such ‘clinical’ categories as schizoid, autistic, ‘impoverished’ affect … all presuppose that there are reliable, valid impersonal criteria for making attributions about the other person’s relation to [his or her] actions. There are no such reliable or valid criteria”.

Differential Diagnosis

Blunted affect is very similar to anhedonia, which is the decrease or cessation of all feelings of pleasure (which thus affects enjoyment, happiness, fun, interest, and satisfaction). In the case of anhedonia, emotions relating to pleasure will not be expressed as much or at all because they are literally not experienced or are decreased. Both blunted affect and anhedonia are considered negative symptoms of schizophrenia, meaning that they are indicative of a lack of something. There are some other negative symptoms of schizophrenia which include avolition, alogia and catatonic behaviour.

Closely related is alexithymia – a condition describing people who “lack words for their feelings. They seem to lack feelings altogether, although this may actually be because of their inability to express emotion rather than from an absence of emotion altogether”. Alexithymic patients however can provide clues via assessment presentation which may be indicative of emotional arousal.

“If the amygdala is severed from the rest of the brain, the result is a striking inability to gauge the emotional significance of events; this condition is sometimes called ‘affective blindness'”. In some cases, blunted affect can fade, but there is no conclusive evidence of why this can occur.

What is an Atypical Antidepressant?

Introduction

An atypical antidepressant is any antidepressant medication that acts in a manner that is different from that of most other antidepressants.

Refer to Second-Generation Antidepressant, Tricyclic Antidepressant, and Tetracyclic Antidepressant.

Background

Atypical antidepressants include agomelatine, bupropion, mianserin, mirtazapine, nefazodone, opipramol, tianeptine, and trazodone. The agents vilazodone and vortioxetine are partly atypical. Typical antidepressants include the SSRIs, SNRIs, TCAs, and MAOIs, which act mainly by increasing the levels of the monoamine neurotransmitters serotonin and/or norepinephrine. Among TCAs, trimipramine is an atypical agent in that it appears not to do this. In August 2020, Esketamine (JNJ-54135419) was approved by the US Food and Drug Administration (FDA) for the treatment for treatment-resistant depression with the added indication for the short-term treatment of suicidal thoughts.

Buprenorphine/Samidorphan (ALKS-5461) is an antidepressant with a novel mechanism of action which is under development and is considered an atypical antidepressant. They act faster than available antidepressants.

What is a Second-Generation Antidepressant?

Introduction

The second-generation antidepressants are a class of antidepressants characterised primarily by the era of their introduction, approximately coinciding with the 1970s and 1980s, rather than by their chemical structure or by their pharmacological effect. As a consequence, there is some controversy over which treatments actually belong in this class.

Refer to Atypical Antidepressant, Tricyclic Antidepressant, and Tetracyclic Antidepressant.

The term “third generation antidepressant” is sometimes used to refer to newer antidepressants, from the 1990s and 2000s, often selective serotonin reuptake inhibitors (SSRIs) such as; fluoxetine (Prozac), paroxetine (Paxil) and sertraline (Zoloft), as well as some non-SSRI antidepressants such as mirtazapine, nefazodone, venlafaxine, duloxetine and reboxetine. However, this usage is not universal.

Examples

This list is not exhaustive, and different sources vary upon which items should be considered second-generation.

  • Amineptine.
  • Amoxapine.
  • Bupropion.
  • Iprindole.
  • Maprotiline.
  • Medifoxamine.
  • Mianserin.
  • Nomifensine.
  • Tianeptine.
  • Trazodone.
  • Venlafaxine.
  • Viloxazine.

An Overview of the Treatment of Bipolar Disorder

Introduction

The emphasis of the treatment of bipolar disorder is on effective management of the long-term course of the illness, which can involve treatment of emergent symptoms.

Treatment methods include pharmacological and psychological techniques.

Principles

The primary treatment for bipolar disorder consists of medications called mood stabilisers, which are used to prevent or control episodes of mania or depression. Medications from several classes have mood stabilising activity. Many individuals may require a combination of medication to achieve full remission of symptoms. As it is impossible to predict which medication will work best for a particular individual, it may take some trial and error to find the best medication or combination for a specific patient. Psychotherapy also has a role in the treatment of bipolar disorder. The goal of treatment is not to cure the disorder but rather to control the symptoms and the course of the disorder. Generally speaking, maintenance treatment of bipolar disorder continues long after symptom control has been achieved.

Following diagnostic evaluation, the treating clinician must determine the optimal treatment setting in order to ensure the patient’s safety. Assessment of suicide risk is key, as the rate of suicide completion among those with bipolar disorder may be as high as 10-15%. Hospitalisation should be considered in patients whose judgement is significantly impaired by their illness, and those who have not responded to outpatient treatment; this may need to be done on an involuntary basis. Treatment setting should regularly be re-evaluated to ensure that it is optimal for the patient’s needs.

Mood Stabilisers

Lithium Salts

Lithium salts have been used for centuries as a first-line treatment for bipolar disorder. In ancient times, doctors would send their mentally ill patients to drink from “alkali springs” as a treatment. Although they were not aware of it, they were actually prescribing lithium, which was present in high concentration within the waters. The therapeutic effect of lithium salts appears to be entirely due to the lithium ion, Li+.

Its exact mechanism of action is uncertain, although there are several possibilities such as inhibition of inositol monophosphatase, modulation of G proteins or regulation of gene expression for growth factors and neuronal plasticity. There is strong evidence for its effectiveness in acute treatment and prevention of recurrence of mania. It can also be effective in bipolar depression, although the evidence is not as strong. It is also effective in reducing the risk of suicide in patients with mood disorders.

Potential side effects from lithium include gastrointestinal upset, tremor, sedation, excessive thirst, frequent urination, cognitive problems, impaired motor coordination, hair loss, and acne. Excessive levels of lithium can be harmful to the kidneys, and increase the risk of side effects in general. As a result, kidney function and blood levels of lithium are monitored in patients being treated with lithium. Therapeutic plasma levels of lithium range from 0.5 to 1.5 mEq/L, with levels of 0.8 or higher being desirable in acute mania.

Lithium levels should be above 0.6 mEq/L to reduce both manic and depressive episodes in patients. A recent review concludes that the standard lithium serum level should be 0.60-0.80 mmol/L with optional reduction to 0.40-0.60 mmol/L in case of good response but poor tolerance or an increase to 0.80-1.00 mmol/L in case of insufficient response and good tolerance.

Monitoring is generally more frequent when lithium is being initiated, and the frequency can be decreased once a patient is stabilised on a given dose. Thyroid hormones should also be monitored periodically, as lithium can increase the risk of hypothyroidism.

Anticonvulsants

A number of anti-convulsant drugs are used as mood stabilisers, and the suspected mechanism is related to the theory that mania can “kindle” further mania, similar to the kindling model of seizures. Valproic acid, or valproate, was one of the first anti-convulsants tested for use in bipolar disorder. It has proven to be effective for treating acute mania. The mania prevention and antidepressant effects of valproic acid have not been well demonstrated. Valproic acid is less effective than lithium at preventing and treating depressive episodes.

Carbamazepine was the first anti-convulsant shown to be effective for treating bipolar mania. It has not been extensively studied in bipolar depression. It is generally considered a second-line agent due to its side effect profile. Lamotrigine is considered a first-line agent for the treatment of bipolar depression. It is effective in preventing the recurrence of both mania and depression, but it has not proved useful in treating acute mania.

Zonisamide (trade name Zonegran), another anti-convulsant, also may show promise in treating bipolar depression. Various other anti-convulsants have been tested in bipolar disorder, but there is little evidence of their effectiveness. Other anti-convulsants effective in some cases and being studied closer include phenytoin, levetiracetam, pregabalin and valnoctamide.

Each anti-convulsant agent has a unique side-effect profile. Valproic acid can frequently cause sedation or gastrointestinal upset, which can be minimised by giving the related drug divalproex, which is available in an enteric-coated tablet. These side effects tend to disappear over time. According to studies conducted in Finland in patients with epilepsy, valproate may increase testosterone levels in teenage girls and produce polycystic ovary syndrome in women who began taking the medication before age 20. Increased testosterone can lead to polycystic ovary syndrome with irregular or absent menses, obesity, and abnormal growth of hair. Therefore, young female patients taking valproate should be monitored carefully by a physician. Excessive levels of valproate can lead to impaired liver function, and liver enzymes and serum valproate level, with a target of 50–125 µg/L, should be monitored periodically.

Side effects of carbamazepine include blurred vision, double vision, ataxia, weight gain, nausea, and fatigue, as well as some rare but serious side effects such as blood dyscrasias, pancreatitis, exfoliative dermatitis, and hepatic failure. Monitoring of liver enzymes, platelets, and blood cell counts are recommended.

Lamotrigine generally has minimal side effects, but the dose must be increased slowly to avoid rashes, including exfoliative dermatitis.

Atypical Antipsychotic Drugs

Antipsychotics work best in the manic phase of bipolar disorder. Second-generation or atypical antipsychotics (including aripiprazole, olanzapine, quetiapine, paliperidone, risperidone, and ziprasidone) have emerged as effective mood stabilisers. The evidence for this is fairly recent, as in 2003 the American Psychiatric Press noted that atypical anti-psychotics should be used as adjuncts to other anti-manic drugs because their mood stabilising properties had not been well established. The mechanism is not well known, but may be related to effects on glutamate activity. Several studies have shown atypical antipsychotics to be effective both as single-agent and adjunctive treatments. Antidepressant effectiveness varies, which may be related to different serotonergic and dopaminergic receptor binding profiles. Quetiapine and the combination of olanzapine and fluoxetine have both demonstrated effectiveness in bipolar depression.

In light of recent evidence, olanzapine (Zyprexa) has been US Food and Drug Administration (FDA) approved as an effective monotherapy for the maintenance of bipolar disorder. A head-to-head randomised control trial (RCT) in 2005 has also shown olanzapine monotherapy to be just as effective and safe as lithium in prophylaxis.

The atypical antipsychotics differ somewhat in side effect profiles, but most have some risk of sedation, weight gain, and extrapyramidal symptoms (including tremor, stiffness, and restlessness). They may also increase the risk of metabolic syndrome, so metabolic monitoring should be performed regularly, including checks of serum cholesterol, triglycerides, and glucose, weight, blood pressure, and waist circumference. Taking antipsychotics for long periods or at high doses can also cause tardive dyskinesia – a sometimes incurable neurological disorder resulting in involuntary, repetitive body movements. The risk of tardive dyskinesia appears to be lower in second-generation antipsychotics than in first-generation antipsychotics but as with first-generation drugs, increases with time spent on medications and in older patients.

New Treatments

A variety of other agents have been tried in bipolar disorder, including benzodiazepines, calcium channel blockers, L-methylfolate, and thyroid hormone. Modafinil (Provigil) and Pramipexole (Mirapex) have been suggested for treating cognitive dysfunction associated with bipolar depression, but evidence supporting their use is quite limited. In addition riluzole, a glutamatergic drug used in ALS has been studied as an adjunct or monotherapy treatment in bipolar depression, with mixed and inconsistent results. The selective oestrogen receptor modulator medication tamoxifen has shown rapid and robust efficacy treating acute mania in bipolar patients. This action is likely due not to tamoxifen’s oestrogen-modulating properties, but due to its secondary action as an inhibitor of protein Kinase C.

Cognitive Effects of Mood Stabilisers

Bipolar patients taking antipsychotics have lower scores on tests of memory and full-scale IQ than patients taking other mood stabilisers. Use of both typical and atypical antipsychotics is associated with risk of cognitive impairment, but the risk is higher for antipsychotics with more sedating effects.

Among bipolar patients taking anticonvulsants, those on lamotrigine have a better cognitive profile than those on carbamazepine, valproate, topiramate, and zonisamide.

Although decreased verbal memory and slowed psychomotor speed are common side effects of lithium use these side effects usually disappear after discontinuation of lithium. Lithium may be protective of cognitive function in the long term since it promotes neurogenesis in the hippocampus and increases grey matter volume in the prefrontal cortex.

Antidepressants

Antidepressants should only be used with caution in bipolar disorder, as they may not be effective and may even induce mania. They should not be used alone, but may be considered as an adjunct to lithium.

A recent large-scale study found that severe depression in patients with bipolar disorder responds no better to a combination of antidepressant medications and mood stabilisers than it does to mood stabilisers alone and that antidepressant use does not hasten the emergence of manic symptoms in patients with bipolar disorder.

The concurrent use of an antidepressant and a mood stabiliser, instead of mood stabiliser monotherapy, may lower the risk of further bipolar depressive episodes in patients whose most recent depressive episode has been resolved. However, some studies have also found that antidepressants pose a risk of inducing hypomania or mania, sometimes in individuals with no prior history of mania. Saint John’s Wort, although a naturally occurring compound, is thought to function in a fashion similar to man-made antidepressants, and so unsurprisingly, there are reports that suggest that it can also induce mania. For these reasons, some psychiatrists are hesitant to prescribe antidepressants for the treatment of bipolar disorder unless mood stabilisers have failed to have an effect, however, others feel that antidepressants still have an important role to play in treatment of bipolar disorder.

Side effects vary greatly among different classes of antidepressants.

Antidepressants are helpful in preventing suicides in people suffering from bipolar disorder when they go in for the depressive phase.

NMDA-Receptor Antagonists

In a double-blind, placebo-controlled, proof-of-concept study, researchers administered an N-methyl-d-aspartate-receptor antagonist (ketamine) to 18 patients already on treatment with lithium (10 patients) or valproate (8 patients) for bipolar depression. From 40 minutes following intravenous injection of ketamine hydrochloride (0.5 mg/kg), the researchers observed significant improvements in depressive symptoms, as measured by standard tools, that were maintained for up to 3 days, an effect not observed in subjects who received the placebo. Five subjects dropped out of the ketamine study; of these, four were taking valproate and one was being treated with lithium. One patient showed signs of hypomania following ketamine administration and two experienced low mood. This study demonstrates a rapid-onset antidepressant effect of ketamine in a small group of patients with bipolar depression. The authors acknowledged the study’s limitations, including the dissociative disturbances in patients receiving ketamine that could have compromised the study blinding, and they emphasised the need for further research.

A more recent double-blind, placebo-controlled study by the same group found that ketamine treatment resulted in a similarly rapid alleviation of suicidal ideation in 15 patients with bipolar depression.

Ketamine is used as a dissociative anaesthetic, and is a Class C substance in the United Kingdom; as such, it should only be used under the direction of a health professional.

Dopamine Agonists

In a single controlled study of twenty one patients, the dopamine D3 receptor agonist pramipexole was found to be highly effective in the treatment of bipolar depression. Treatment was initiated at 0.125 mg t.i.d. and increased at a rate of 0.125 mg t.i.d. to a limit of 4.5 mg qd until the patients’ condition satisfactorily responded to the medication or they could not abide the side effects. The final average dosage was 1.7 mg ± .90 mg qd. The incidence of hypomania in the treatment group was no greater than in the control group.

Psychotherapy

Certain types of psychotherapy, used in combination with medication, may provide some benefit in the treatment of bipolar disorders. Psychoeducation has been shown to be effective in improving patients’ compliance with their lithium treatment. Evidence of the efficacy of family therapy is not adequate to support unrestricted recommendation of its use. There is “fair support” for the utility of cognitive therapy. Evidence for the efficacy of other psychotherapies is absent or weak, often not being performed under randomised and controlled conditions. Well-designed studies have found interpersonal and social rhythm therapy to be effective.

Although medication and psychotherapy cannot cure the illness, therapy can often be valuable in helping to address the effects of disruptive manic or depressive episodes that have hurt a patient’s career, relationships or self-esteem. Therapy is available not only from psychiatrists but from social workers, psychologists and other licensed counsellors.

Jungian Therapy

Jungian authors have likened the mania and depression of bipolar disorder to the Jungian archetypes ‘puer’ and ‘senex’. The puer archetype is defined by the behaviours of spontaneity, impulsiveness, enthusiasm or mania and is symbolised by characters such as Peter Pan or the Greek god Hermes. The senex archetype is defined by behaviours of order, systematic thought, caution, and depression and is symbolised by characters such as the Roman god Saturn or the Greek god Kronos. Jungians conceptualise the puer and senex as a coexistent bipolarity appearing in human behaviour and imagination, but in neurotic manifestations appears as extreme oscillations and as unipolar manifestations. In the case of the split puer-senex bipolarity the therapeutic task is to bring the puer and senex back into correlation by working with the patient’s mental imagery.”

Lifestyle Changes

Sufficient Sleep

If sleeping is disturbed, the symptoms can occur. Sleep disruption may actually exacerbate the mental illness state. Those who do not get enough sleep at night, sleep late and wake up late, or go to sleep with some disturbance (e.g. music or charging devices) have a greater chance of having the symptoms and, in addition, depression. It is highly advised to not sleep too late and to get enough high quality sleep.

Self-Management and Self-Awareness

Understanding the symptoms, when they occur and ways to control them using appropriate medications and psychotherapy has given many people diagnosed with bipolar disorder a chance at a better life. Prodrome symptom detection has been shown to be used effectively to anticipate onset of manic episodes and requires high degree of understanding of one’s illness. Because the offset of the symptoms is often gradual, recognising even subtle mood changes and activity levels is important in avoiding a relapse. Maintaining a mood chart is a specific method used by patients and doctors to identify mood, environmental and activity triggers.

Stress Reduction

Forms of stress may include having too much to do, too much complexity and conflicting demands among others. There are also stresses that come from the absence of elements such as human contact, a sense of achievement, constructive creative outlets, and occasions or circumstances that will naturally elicit positive emotions. Stress reduction will involve reducing things that cause anxiety and increasing those that generate happiness. It is not enough to just reduce the anxiety.

Co-Morbid Substance Use Disorder

Co-occurring substance misuse disorders, which are extremely common in bipolar patients can cause a significant worsening of bipolar symptomatology and can cause the emergence of affective symptoms. The treatment options and recommendations for substance use disorders is wide but may include certain pharmacological and nonpharmacological treatment options.

Other Treatments

Omega-3 Fatty Acids

Omega-3 fatty acids may also be used as a treatment for bipolar disorder, particularly as a supplement to medication. An initial clinical trial by Stoll et al. (1999) produced positive results. However, since 1999 attempts to confirm this finding of beneficial effects of omega-3 fatty acids in several larger double-blind clinical trials have produced inconclusive results. It was hypothesized that the therapeutic ingredient in omega-3 fatty acid preparations is eicosapentaenoic acid (EPA) and that supplements should be high in this compound to be beneficial. A 2008 Cochrane systematic review found limited evidence to support the use of Omega-3 fatty acids to improve depression but not mania as an adjunct treatment for bipolar disorder.

Omega-3 fatty acids may be found in fish, fish oils, algae, and to a lesser degree in other foods such as flaxseed, flaxseed oil and walnuts. Although the benefits of Omega-3 fatty acids remain debated, they are readily available at drugstores and supermarkets, relatively inexpensive, and have few known side effects (All of these oils, however, have the capacity to exacerbate GERD (gastroesophageal reflux disease) – food sources may be a good alternative in such cases).

Exercise

Exercise has also been shown to have antidepressant effects.

Electroconvulsive Therapy

Electroconvulsive therapy (ECT) may have some effectiveness in mixed mania states, and good effectiveness in bipolar depression, particularly in the presence of psychosis. It may also be useful in the treatment of severe mania that is non-responsive to medications.

The most frequent side effects of ECT include memory impairment, headaches, and muscle aches. In some instances, ECT can produce significant and long-lasting cognitive impairment, including anterograde amnesia, and retrograde amnesia.

Ketogenic Diet

Because many of the medications that are effective in treating epilepsy are also effective as mood stabilizers, it has been suggested that the ketogenic diet – used for treating paediatric epilepsy – could have mood stabilising effects. Ketogenic diets are diets that are high in fat and low in carbohydrates, and force the body to use fat for energy instead of sugars from carbohydrates. This causes a metabolic response similar to that seen in the body during fasting. This idea has not been tested by clinical research, and until recently, was entirely hypothetical. Recently, however, two case studies have been described where ketogenic diets were used to treat bipolar II. In each case, the patients found that the ketogenic diet was more effective for treating their disorder than medication and were able to discontinue the use of medication. The key to efficacy appears to be ketosis (a metabolic state characterised by elevated levels of ketone bodies in the blood or urine), which can be achieved either with a classic high-fat ketogenic diet, or with a low-carbohydrate diet similar to the induction phase of the Atkins Diet. The mechanism of action is not well understood. It is unclear whether the benefits of the diet produce a lasting improvement in symptoms (as is sometimes the case in treatment for epilepsy) or whether the diet would need to be continued indefinitely to maintain symptom remission.

The Role of Cannabinoids

Acute cannabis intoxication transiently produces perceptual distortions, psychotic symptoms and reduction in cognitive abilities in healthy persons and in severe mental disorder, and may impair the ability to safely operate a motor vehicle.

Cannabis use is common in bipolar disorder, and is a risk factor for a more severe course of the disease by increasing frequency and duration of episodes. It is also reported to reduce age at onset.

Alternative Medicine

Several studies have suggested that omega-3 fatty acids may have beneficial effects on depressive symptoms, but not manic symptoms. However, only a few small studies of variable quality have been published and there is not enough evidence to draw any firm conclusions.

What is Seproxetine?

Introduction

Seproxetine, also known as (S)-norfluoxetine, is a selective serotonin reuptake inhibitor (SSRI).

Background

It is the S enantiomer of norfluoxetine, the main active metabolite of the widely used antidepressant fluoxetine; but little is known about its pharmacological actions. Seproxetine was being investigated by Eli Lilly and Company as an antidepressant; however, cardiac side effects were discovered and development was discontinued.

What is Desvenlafaxine?

Introduction

Desvenlafaxine, sold under the brand name Pristiq among others, is a medication used to treat depression.

It is recommended that the need for further treatment be occasionally reassessed. It may be less effective than its parent compound venlafaxine, although some studies have found comparable efficacy. It is an antidepressant of the serotonin-norepinephrine reuptake inhibitor (SNRI) class and is taken by mouth.

Common side effects include dizziness, trouble sleeping, increased sweating, constipation, sleepiness, anxiety, and sexual problems. Serious side effects may include suicide in those under the age of 25, serotonin syndrome, bleeding, mania, and high blood pressure. A withdrawal syndrome may occur if the dose is rapidly decreased. It is unclear if use during pregnancy or breastfeeding is safe.

Desvenlafaxine was approved for medical use in the United States in 2008. In Europe its application for use was denied in 2009. In 2017, it was the 235th most commonly prescribed medication in the United States, with more than two million prescriptions.

Medical Uses

Desvenlafaxine is primarily used as a treatment for major depressive disorder. Use has only been studied up to 8 weeks. It may be less effective than venlafaxine, although some studies have found comparable efficacy with a lower rate of nausea.

Doses of 50-400 mg/day appear effective for major depressive disorder, although no additional benefit was demonstrated at doses greater than 50 mg/day, and adverse events and discontinuations were more frequent at higher doses.

Desvenlafaxine improves the HAM-D17 score and measures of well being such as the Sheehan Disability Scale (SDS) and 5-item World Health Organisation Well-Being Index (WHO-5).

Adverse Effects

Frequency of adverse effects:

  • Very common adverse effects include:
    • Nausea.
    • Headache.
    • Dizziness.
    • Dry mouth.
    • Hyperhidrosis.
    • Diarrhoea.
    • Insomnia.
    • Constipation.
    • Fatigue.
  • Common adverse effects include:
    • Tremor.
    • Blurred vision.
    • Mydriasis.
    • Decreased appetite.
    • Sexual dysfunction.
    • Insomnia.
    • Anxiety.
    • Elevated cholesterol and triglycerides.
    • Proteinuria.
    • Vertigo.
    • Feeling jittery.
    • Asthenia.
    • Nervousness.
    • Hot flush.
    • Irritability.
    • Abnormal dreams.
    • Urinary hesitation.
    • Yawning.
    • Rash.
  • Uncommon adverse effects include:
  • Rare adverse effects include:
    • Hyponatraemia (low blood sodium).
    • Seizures.
    • Extrapyramidal side effects.
    • Hallucinations.
    • Angioedema.
    • Photosensitivity reaction.
    • Stevens-Johnson syndrome.
  • Common however unknown intensity of adverse effects include:
    • Abnormal bleeding (gastrointestinal bleeds).
    • Narrow-angle glaucoma.
    • Mania.
    • Interstitial lung disease.
    • Eosinophilic pneumonia.
    • Hypertension.
    • Suicidal behaviour and thoughts.
    • Serotonin syndrome.

Pharmacology

Desvenlafaxine is a synthetic form of the isolated major active metabolite of venlafaxine, and is categorised as a serotonin-norepinephrine reuptake inhibitor (SNRI). When most normal metabolisers take venlafaxine, approximately 70% of the dose is metabolised into desvenlafaxine, so the effects of the two drugs are expected to be very similar. It works by blocking the “reuptake” transporters for key neurotransmitters affecting mood, thereby leaving more active neurotransmitters in the synapse. The neurotransmitters affected are serotonin (5-hydroxytryptamine) and norepinephrine (noradrenaline). It is approximately 10 times more potent at inhibiting serotonin uptake than norepinephrine uptake.

Approval Status

United States

Wyeth announced on 23 January 2007 that it received an approvable letter from the Food and Drug Administration (FDA) for desvenlafaxine. Final approval to sell the drug was contingent on a number of things, including:

  • A satisfactory FDA inspection of Wyeth’s Guayama, Puerto Rico facility, where the drug is to be manufactured;
  • Several postmarketing surveillance commitments, and follow-up studies on low-dose use, relapse, and use in children;
  • Clarity by Wyeth around the company’s product education plan for physicians and patients;
  • Approval of desvenlafaxine’s proprietary name, Pristiq.

The FDA approved the drug for antidepressant use in February 2008, and was to be available in US pharmacies in May 2008.

In March 2017, the generic form of the drug was made available in the US.

Canada

On 04 February 2009, Health Canada approved use of desvenlafaxine for treatment of depression.

European Union

In 2009, an application to market desvenlafaxine for major depressive disorder in the European Union was declined. In 2012, Pfizer received authorization in Spain to market desvenlafaxine for the disorder but it is not being sold.

Australia

Desvenlafaxine is classified as a schedule 4 (prescription only) drug in Australia. It was listed on the PBS (Pharmaceutical Benefits Scheme) in 2008 for the treatment of major depressive disorders.