Tag: SAD: Seasonal Affective Disorder

What is Light Therapy?

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Introduction

Light therapy – or phototherapy, classically referred to as heliotherapy – is a method recognised by scientific medicine for the treatment of various diseases. It includes exposure to outdoor daylight or specific indoor artificial light sources.

Example of light therapy for winter depression.

The care guideline for unipolar depression recommends light therapy especially for depression that follows a seasonal pattern (seasonal affective disorder). There is tentative evidence to support its use to treat depressive disorders that are not seasonally dependent. As a treatment for disorders of the skin, the second kind of light therapy, called ultraviolet light therapy, is meant to treat neurodermatitis, psoriasis, acne vulgaris, eczema and neonatal jaundice.

Brief History

Many ancient cultures practiced various forms of heliotherapy, including people of Ancient Greece, Ancient Egypt, and Ancient Rome. The Inca, Assyrian and early German settlers also worshipped the sun as a health bringing deity. Indian medical literature dating to 1500 BCE describes a treatment combining herbs with natural sunlight to treat non-pigmented skin areas. Buddhist literature from about 200 CE and 10th-century Chinese documents make similar references.

The Faroese physician Niels Finsen is believed to be the father of modern phototherapy. He developed the first artificial light source for this purpose. Finsen used short wavelength light to treat lupus vulgaris, a skin infection caused by Mycobacterium tuberculosis. He thought that the beneficial effect was due to ultraviolet light killing the bacteria, but recent studies showed that his lens and filter system did not allow such short wavelengths to pass through, leading instead to the conclusion that light of approximately 400 nanometers generated reactive oxygen that would kill the bacteria. Finsen also used red light to treat smallpox lesions. He received the Nobel Prize in Physiology or Medicine in 1903. Scientific evidence for some of his treatments is lacking, and later eradication of smallpox and development of antibiotics for tuberculosis rendered light therapy obsolete for these diseases.

From the late nineteenth century until the early 1930s, light therapy was considered an effective and mainstream medical therapy in the UK for conditions such as varicose ulcer, ‘sickly children’ and a wide range of other conditions. Controlled trials by the medical scientist Dora Colebrook, supported by the Medical Research Council, indicated that light therapy was not effective for such a wide range of conditions.

Medical Uses

Skin Conditions

Light therapy treatments for the skin usually involve exposure to ultraviolet light. The exposures can be to a small area of the skin or over the whole body surface, as in a tanning bed. The most common treatment is with narrowband UVB, which has a wavelength of approximately 311-313 nanometers. Exposure to photons (light) at these specific wavelengths enables the body to produce vitamin D. Full body phototherapy can be delivered at a doctor’s office or at home using a large high-power UVB booth. Tanning beds, however, generate mostly UVA light, and only 4% to 10% of tanning bed light is in the UVB spectrum.

Atopic Dermatitis

Light therapy is considered one of the best monotherapy treatments for atopic dermatitis (AD) when applied to patients who have not responded to traditional topical treatments. The therapy offers a wide range of options: UVA1 for acute AD, NB-UVB for chronic AD, and balneophototherapy have proven their efficacy. Patients tolerate the therapy safely but, as in any therapy, there are potential adverse effects and care must be taken in its application, particularly to children.

Psoriasis

For psoriasis, UVB phototherapy has been shown to be effective. A feature of psoriasis is localised inflammation mediated by the immune system. Ultraviolet radiation is known to suppress the immune system and reduce inflammatory responses. Light therapy for skin conditions like psoriasis usually use 313 nanometer UVB though it may use UVA (315-400 nm wavelength) or a broader spectrum UVB (280-315 nm wavelength). UVA combined with psoralen, a drug taken orally, is known as PUVA treatment. In UVB phototherapy the exposure time is very short, seconds to minutes depending on intensity of lamps and the person’s skin pigment and sensitivity.

Vitiligo

About 1% of the human population suffers from vitiligo which causes painless distinct light-coloured patches of the skin on the face, hands, and legs. Phototherapy is an effective treatment because it forces skin cells to manufacture melanin to protect the body from UV damage. Prescribed treatment is generally 3 times a week in a clinic or daily at home. About 1 month usually results in re-pigmentation in the face and neck, and 2-4 months in the hands and legs. Narrowband UVB is more suitable to the face and neck and PUVA is more effective at the hands and legs.]

Acne Vulgaris

As of 2012 evidence for light therapy and lasers in the treatment of acne vulgaris was not sufficient to recommend them. There is moderate evidence for the efficacy of blue and blue-red light therapies in treating mild acne, but most studies are of low quality. While light therapy appears to provide short-term benefit, there is a lack of long-term outcome data or data in those with severe acne.

Cancer

According to the American Cancer Society, there is some evidence that ultraviolet light therapy may be effective in helping treat certain kinds of skin cancer, and ultraviolet blood irradiation therapy is established for this application. However, alternative uses of light for cancer treatment – light box therapy and coloured light therapy – are not supported by evidence. Photodynamic therapy (often with red light) is used to treat certain superficial non-melanoma skin cancers.

Other Skin Conditions

Some types of phototherapy may be effective in the treatment of polymorphous light eruption, cutaneous T-cell lymphoma and lichen planus. Narrowband UVB between 311-313 nanometers is the most common treatment.

Wound Healing

Low level laser therapy has been studied as a potential treatment for chronic wounds, and higher-power lasers have sometimes been successfully used to close acute wounds as an alternative to stitching. However, as of 2012 and due to inconsistent results and the low quality of extant research, reviews in the scientific literature have not supported its widespread application.

Retinal Conditions

There is preliminary evidence that light therapy is an effective treatment for diabetic retinopathy and diabetic macular oedema.

Mood and Sleep Related

Seasonal Affective Disorder

The effectiveness of light therapy for treating seasonal affective disorder (SAD) may be linked to the fact that light therapy makes up for lost sunlight exposure and resets the body’s internal clock. Studies show that light therapy helps reduce the debilitating and depressive behaviours of SAD, such as excessive sleepiness and fatigue, with results lasting for at least 1 month. Light therapy is preferred over antidepressants in the treatment of SAD because it is a relatively safe and easy therapy. Two methods of light therapy, bright light and dawn simulation, have similar success rates in the treatment of SAD.

It is possible that response to light therapy for SAD could be season dependent. Morning therapy has provided the best results because light in the early morning aids in regulating the circadian rhythm. People affected by SAD have low levels of energy and have difficulty concentrating. They usually have a change in appetite and experience trouble sleeping.

A 2007 systematic review by the Swedish agency SBU found insufficient evidence that light therapy was able to alleviate symptoms of depression or seasonal affective disorder. The report recommended that: “Approximately 100 participants are required to establish whether the therapy is moderately more effective than placebo”. Although treatment in light therapy rooms was well established in Sweden, no satisfactory, controlled studies had been published on the subject. This led to the closure of a number of clinics offering light therapy in Sweden.

A Cochrane review conducted in 2019 states the evidence that light therapy’s effectiveness as a treatment for the prevention of seasonal affective disorder is limited, although the risk of adverse effects are minimal. Therefore, the decision to use light therapy should be based on a person’s preference of treatment.

Non-Seasonal Depression

Light therapy has also been suggested in the treatment of non-seasonal depression and other psychiatric mood disturbances, including major depressive disorder, bipolar disorder and postpartum depression. A meta-analysis by the Cochrane Collaboration concluded that “for patients suffering from non-seasonal depression, light therapy offers modest though promising antidepressive efficacy.” A 2008 systematic review concluded that “overall, bright light therapy is an excellent candidate for inclusion into the therapeutic inventory available for the treatment of nonseasonal depression today, as adjuvant therapy to antidepressant medication, or eventually as stand-alone treatment for specific subgroups of depressed patients.” A 2015 review found that supporting evidence for light therapy was limited due to serious methodological flaws.

A 2016 meta-analysis showed that bright light therapy appeared to be efficacious, particularly when administered for 2-5 weeks’ duration and as monotherapy.

Chronic Circadian Rhythm Sleep Disorders (CRSD)

In the management of circadian rhythm disorders such as delayed sleep phase disorder (DSPD), the timing of light exposure is critical. Light exposure administered to the eyes before or after the nadir of the core body temperature rhythm can affect the phase response curve. Use upon awakening may also be effective for non-24-hour sleep-wake disorder. Some users have reported success with lights that turn on shortly before awakening (dawn simulation). Evening use is recommended for people with advanced sleep phase disorder. Some, but not all, totally blind people whose retinae are intact, may benefit from light therapy.

Situational Circadian Rhythm Sleep Disorder (CRSD)

Light therapy has been tested for individuals with shift work sleep disorder and for jet lag.

Sleep Disorder in Parkinson’s Disease

Light therapy has been trialled in treating sleep disorders experienced by patients with Parkinson’s disease.

Sleep Disorder in Alzheimer’s Disease

Studies have shown that daytime and evening light therapy for nursing home patients with Alzheimer’s disease, who often struggle with agitation and fragmented wake/rest cycles effectively led to more consolidated sleep and an increase in circadian rhythm stability.

Neonatal Jaundice (Postnatal Jaundice)

Light therapy is used to treat cases of neonatal jaundice. Bilirubin, a yellow pigment normally formed in the liver during the breakdown of old red blood cells, cannot always be effectively cleared by a neonate’s liver causing neonatal jaundice. Accumulation of excess bilirubin can cause central nervous system damage, and so this buildup of bilirubin must be treated. Phototherapy uses the energy from light to isomerize the bilirubin and consequently transform it into compounds that the newborn can excrete via urine and stools. Bilirubin is most successful absorbing light in the blue region of the visible light spectrum, which falls between 460-490 nm. Therefore light therapy technologies that utilise these blue wavelengths are the most successful at isomerising bilirubin.

Techniques

Photodynamic Therapy

Photodynamic therapy is a form of phototherapy using nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells.

One of the treatments is using blue light with aminolevulinic acid for the treatment of actinic keratosis. This is not a U.S. FDA-approved treatment for acne vulgaris.

Light Boxes

The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness as registered by photosensitive ganglion cells in the retina. To some degree, the reverse is true for serotonin, which has been linked to mood disorders. Hence, for the purpose of manipulating melatonin levels or timing, light boxes providing very specific types of artificial illumination to the retina of the eye are effective.

Light therapy uses either a light box which emits up to 10,000 lux of light at a specified distance, much brighter than a customary lamp, or a lower intensity of specific wavelengths of light from the blue (460 nm) to the green (525 nm) areas of the visible spectrum. A 1995 study showed that green light therapy at doses of 350 lux produces melatonin suppression and phase shifts equivalent to 10,000 lux white light therapy, but another study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination, because of a possible involvement of the cones in melatonin suppression.

Child patients with external forms of tuberculosis, especially of the bones and joints, laying on beds on a terrace outside Treloar Hospital in Alton, Hampshire, England, in sunlight as part of their light therapy, ca. first half of the 20th century.

Risks and Complications

Ultraviolet

Ultraviolet light causes progressive damage to human skin and erythema even from small doses. This is mediated by genetic damage, collagen damage, as well as destruction of vitamin A and vitamin C in the skin and free radical generation. Ultraviolet light is also known to be a factor in formation of cataracts. Ultraviolet radiation exposure is strongly linked to incidence of skin cancer.

Visible Light

Optical radiation of any kind with enough intensity can cause damage to the eyes and skin including photoconjunctivitis and photokeratitis. Researchers have questioned whether limiting blue light exposure could reduce the risk of age-related macular degeneration. According to the American Academy of Ophthalmology, there is no scientific evidence showing that exposure to blue light emitting devices result in eye damage. According to Harriet Hall, blue light exposure is reported to suppress the production of melatonin, which affects our body’s circadian rhythm and can decrease sleep quality. It is reported that bright light therapy may activate the production of reproductive hormones, such as testosterone, luteinizing hormone, follicle-stimulating hormone, and estradiol.

Modern phototherapy lamps used in the treatment of seasonal affective disorder and sleep disorders either filter out or do not emit ultraviolet light and are considered safe and effective for the intended purpose, as long as photosensitising drugs are not being taken at the same time and in the absence of any existing eye conditions. Light therapy is a mood altering treatment, and just as with drug treatments, there is a possibility of triggering a manic state from a depressive state, causing anxiety and other side effects. While these side effects are usually controllable, it is recommended that patients undertake light therapy under the supervision of an experienced clinician, rather than attempting to self-medicate.

Contraindications to light therapy for seasonal affective disorder include conditions that might render the eyes more vulnerable to phototoxicity, tendency toward mania, photosensitive skin conditions, or use of a photosensitising herb (such as St. John’s wort) or medication. Patients with porphyria should avoid most forms of light therapy. Patients on certain drugs such as methotrexate or chloroquine should use caution with light therapy as there is a chance that these drugs could cause porphyria.

Side effects of light therapy for sleep phase disorders include jumpiness or jitteriness, headache, eye irritation and nausea. Some non-depressive physical complaints, such as poor vision and skin rash or irritation, may improve with light therapy.

What is the Seasonal Pattern Assessment Questionnaire?

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Introduction

The Seasonal Pattern Assessment Questionnaire, or SPAQ, is a simple, self-administered screening test for Seasonal Affective Disorder, first developed in 1984. Though some aspects of its accuracy have been questioned since then, it is widely used today, especially by SAD researchers.

Background

The SPAQ is a screening instrument for seasonal affective disorder (SAD), a recurrent major depressive disorder that typically affects its victims during the fall and winter months. It was first developed by American psychiatrist Norman E. Rosenthal and his National Institute of Mental Health colleagues in 1984, and continues to be widely used. It is a self-administered paper-and-pencil test that is freely available in the public domain. The SPAQ can be downloaded.

The questionnaire asks subjects to score the amounts of seasonal changes they have experienced in sleep, socialization, mood, weight, appetite and energy. A global score between 0 and 24 is gotten by adding up the scores on each of these items. Subjects also specify the months during which these changes are greatest and least. Subjects are also asked rate their overall seasonal impairment from “no problem” to “disabling”.

Subjects are often taught how to interpret their scores, and cautioned that a self-assessment can never substitute for a clinical evaluation. If their score on the SPAQ is high, they are advised to consult their physician.

Reliability, Validity, and Specificity

Numerous studies have been done to assess the usefulness of the test. In general, it has been found to be reliable (in that it yields consistent measurements) and valid (in that it measures what it purports to measure). It has also been found to have low specificity (in that people who have other forms of depression can score as if they have SAD). This could give misleadingly high estimates of the prevalence of SAD.

Some studies have questioned the overall validity of the SPAQ, and even the concept of SAD itself.

In spite of its shortcomings, the SPAQ is still a very popular screening tool in SAD research. This is true because of its early development, historically wide dissemination, and the absence of better-validated alternatives.

What is Seasonal Affective Disorder?

Published on by Andrew Marshall3 Comments

Introduction

Seasonal affective disorder (SAD) is a mood disorder subset in which people who have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year, most commonly in winter. Common symptoms include sleeping too much and having little to no energy, and overeating. The condition in the summer can include heightened anxiety.

In the Diagnostic and Statistical Manual of Mental Disorders DSM-IV and DSM-5, its status was changed. It is no longer classified as a unique mood disorder but is now a specifier, called “with seasonal pattern”, for recurrent major depressive disorder that occurs at a specific time of the year and fully remits otherwise. Although experts were initially sceptical, this condition is now recognised as a common disorder.

In the United States, the percentage of the population affected by SAD ranges from 1.4% of the population in Florida, to 9.9% in Alaska. SAD was formally described and named in 1984 by Norman E. Rosenthal and colleagues at the National Institute of Mental Health.

Brief History

SAD was first systematically reported and named in the early 1980s by Norman E. Rosenthal, M.D., and his associates at the National Institute of Mental Health (NIMH). Rosenthal was initially motivated by his desire to discover the cause of his own experience of depression during the dark days of the northern US winter. He theorised that the reduction in available natural light during winter was the cause. Rosenthal and his colleagues then documented the phenomenon of SAD in a placebo-controlled study utilising light therapy. A paper based on this research was published in 1984. Although Rosenthal’s ideas were initially greeted with scepticism, SAD has become well recognised, and his 1993 book, Winter Blues has become the standard introduction to the subject.

Research on SAD in the United States began in 1979 when Herb Kern, a research engineer, had also noticed that he felt depressed during the winter months. Kern suspected that scarcer light in winter was the cause and discussed the idea with scientists at the NIMH who were working on bodily rhythms. They were intrigued, and responded by devising a lightbox to treat Kern’s depression. Kern felt much better within a few days of treatments, as did other patients treated in the same way.

Signs and Symptoms

SAD is a type of major depressive disorder (MDD), and sufferers may exhibit any of the associated symptoms, such as feelings of hopelessness and worthlessness, thoughts of suicide, loss of interest in activities, withdrawal from social interaction, sleep and appetite problems, difficulty with concentrating and making decisions, decreased libido, a lack of energy, or agitation. Symptoms of winter SAD often include oversleeping or difficulty waking up in the morning, nausea, and a tendency to overeat, often with a craving for carbohydrates, which leads to weight gain. SAD is typically associated with winter depression, but springtime lethargy or other seasonal mood patterns are not uncommon. Although each individual case is different, in contrast to winter SAD, people who experience spring and summer depression may be more likely to show symptoms such as insomnia, decreased appetite and weight loss, and agitation or anxiety.

Bipolar Disorder

With seasonal pattern is a specifier for bipolar and related disorders, including bipolar I disorder and bipolar II disorder. Most people with SAD experience major depressive disorder, but as many as 20% may have a bipolar disorder. It is important to discriminate between diagnoses because there are important treatment differences. In these cases, people who have the With seasonal pattern specifier may experience a depressive episode either due to MDD or as part of bipolar disorder during the winter and remit in the summer. Around 25% of patients with bipolar disorder may present with a depressive seasonal pattern, which is associated with bipolar II disorder, rapid cycling, eating disorders, and more depressive episodes. Differences in biological sex display distinct clinical characteristics associated to seasonal pattern: males present with more Bipolar II disorder and a higher number of depressive episodes, and females with rapid cycling and eating disorders.

Cause

In many species, activity is diminished during the winter months in response to the reduction in available food, the reduction of sunlight (especially for diurnal animals) and the difficulties of surviving in cold weather. Hibernation is an extreme example, but even species that do not hibernate often exhibit changes in behaviour during the winter. Presumably, food was scarce during most of human prehistory, and a tendency toward low mood during the winter months would have been adaptive by reducing the need for calorie intake. The preponderance of women with SAD suggests that the response may also somehow regulate reproduction.

Various proximate causes have been proposed. One possibility is that SAD is related to a lack of serotonin, and serotonin polymorphisms could play a role in SAD, although this has been disputed.[20] Mice incapable of turning serotonin into N-acetylserotonin (by serotonin N-acetyltransferase) appear to express “depression-like” behaviour, and antidepressants such as fluoxetine increase the amount of the enzyme serotonin N-acetyltransferase, resulting in an antidepressant-like effect. Another theory is that the cause may be related to melatonin which is produced in dim light and darkness by the pineal gland, since there are direct connections, via the retinohypothalamic tract and the suprachiasmatic nucleus, between the retina and the pineal gland.[citation needed] Melatonin secretion is controlled by the endogenous circadian clock, but can also be suppressed by bright light.

One study looked at whether some people could be predisposed to SAD based on personality traits. Correlations between certain personality traits, higher levels of neuroticism, agreeableness, openness, and an avoidance-oriented coping style, appeared to be common in those with SAD.

Pathophysiology

Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright-light therapy. SAD is measurably present at latitudes in the Arctic region, such as northern Finland (64°00′N), where the rate of SAD is 9.5%. Cloud cover may contribute to the negative effects of SAD. There is evidence that many patients with SAD have a delay in their circadian rhythm, and that bright light treatment corrects these delays which may be responsible for the improvement in patients.

The symptoms of it mimic those of dysthymia or even major depressive disorder. There is also potential risk of suicide in some patients experiencing SAD. One study reports 6-35% of sufferers required hospitalization during one period of illness. At times, patients may not feel depressed, but rather lack energy to perform everyday activities.

Subsyndromal Seasonal Affective Disorder is a milder form of SAD experienced by an estimated 14.3% (vs. 6.1% SAD) of the US population. The blue feeling experienced by both SAD and SSAD sufferers can usually be dampened or extinguished by exercise and increased outdoor activity, particularly on sunny days, resulting in increased solar exposure. Connections between human mood, as well as energy levels, and the seasons are well documented, even in healthy individuals.

Diagnosis

According to the American Psychiatric Association DSM-IV criteria, Seasonal Affective Disorder is not regarded as a separate disorder. It is called a “course specifier” and may be applied as an added description to the pattern of major depressive episodes in patients with major depressive disorder or patients with bipolar disorder.

The “Seasonal Pattern Specifier” must meet four criteria: depressive episodes at a particular time of the year; remissions or mania/hypomania at a characteristic time of year; these patterns must have lasted two years with no non-seasonal major depressive episodes during that same period; and these seasonal depressive episodes outnumber other depressive episodes throughout the patient’s lifetime. The Mayo Clinic describes three types of SAD, each with its own set of symptoms.

Management

Treatments for classic (winter-based) seasonal affective disorder include light therapy, medication, ionized-air administration, cognitive-behavioural therapy (CBT) and carefully timed supplementation of the hormone melatonin.

Light Therapy

Photoperiod-related alterations of the duration of melatonin secretion may affect the seasonal mood cycles of SAD. This suggests that light therapy may be an effective treatment for SAD. Light therapy uses a lightbox which emits far more lumens than a customary incandescent lamp. Bright white “full spectrum” light at 10,000 lux, blue light at a wavelength of 480 nm at 2,500 lux or green (actually cyan or blue-green) light at a wavelength of 500 nm at 350 lux are used, with the first-mentioned historically preferred.

Bright light therapy is effective with the patient sitting a prescribed distance, commonly 30-60 cm, in front of the box with her/his eyes open but not staring at the light source for 30-60 minutes. A study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination. Discovering the best schedule is essential. One study has shown that up to 69% of patients find lightbox treatment inconvenient and as many as 19% stop use because of this.

Dawn simulation has also proven to be effective; in some studies, there is an 83% better response when compared to other bright light therapy. When compared in a study to negative air ionization, bright light was shown to be 57% effective vs. dawn simulation 50%. Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks. Most studies have found it effective without use year round but rather as a seasonal treatment lasting for several weeks until frequent light exposure is naturally obtained.

Light therapy can also consist of exposure to sunlight, either by spending more time outside or using a computer-controlled heliostat to reflect sunlight into the windows of a home or office. Although light therapy is the leading treatment for seasonal affective disorder, prolonged direct sunlight or artificial lights that don’t block the ultraviolet range should be avoided due to the threat of skin cancer.

The evidence base for light therapy as a preventive treatment for seasonal affective disorder is limited. The decision to use light therapy to treat people with a history of winter depression before depressive symptoms begin should be based on a persons preference of treatment.

Medication

SSRI (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD. Effective antidepressants are fluoxetine, sertraline, or paroxetine. Both fluoxetine and light therapy are 67% effective in treating SAD according to direct head-to-head trials conducted during the 2006 Can-SAD study. Subjects using the light therapy protocol showed earlier clinical improvement, generally within one week of beginning the clinical treatment. Bupropion extended-release has been shown to prevent SAD for one in four people, but has not been compared directly to other preventive options in trials.

Modafinil may be an effective and well-tolerated treatment in patients with seasonal affective disorder/winter depression.

Another explanation is that vitamin D levels are too low when people do not get enough Ultraviolet-B on their skin. An alternative to using bright lights is to take vitamin D supplements. However, studies did not show a link between vitamin D levels and depressive symptoms in elderly Chinese nor among elderly British women.

Other Treatments

Depending upon the patient, one treatment (e.g. lightbox) may be used in conjunction with another (e.g. medication).

Negative air ionisation, which involves releasing charged particles into the sleep environment, has been found effective with a 47.9% improvement if the negative ions are in sufficient density (quantity).

Physical exercise has shown to be an effective form of depression therapy, particularly when in addition to another form of treatment for SAD. One particular study noted marked effectiveness for treatment of depressive symptoms when combining regular exercise with bright light therapy. Patients exposed to exercise which had been added to their treatments in 20 minutes intervals on the aerobic bike during the day along with the same amount of time underneath the UV light were seen to make quick recovery.

Of all the psychological therapies aimed at the prevention of SAD, cognitive-behaviour therapy, typically involving thought records, activity schedules and a positive data log, has been the subject of the most empirical work, however, evidence for CBT or any of the psychological therapies aimed at preventing SAD remains inconclusive.

Epidemiology

Nordic Countries

Winter depression is a common slump in the mood of some inhabitants of most of the Nordic countries. It was first described by the 6th century Goth scholar Jordanes in his Getica wherein he described the inhabitants of Scandza (Scandinavia). Iceland, however, seems to be an exception. A study of more than 2000 people there found the prevalence of seasonal affective disorder and seasonal changes in anxiety and depression to be unexpectedly low in both sexes. The study’s authors suggested that propensity for SAD may differ due to some genetic factor within the Icelandic population. A study of Canadians of wholly Icelandic descent also showed low levels of SAD. It has more recently been suggested that this may be attributed to the large amount of fish traditionally eaten by Icelandic people, in 2007 about 90 kilograms per person per year as opposed to about 24 kg in the US and Canada, rather than to genetic predisposition; a similar anomaly is noted in Japan, where annual fish consumption in recent years averages about 60 kg per capita. Fish are high in vitamin D. Fish also contain docosahexaenoic acid (DHA), which help with a variety of neurological dysfunctions.

Other Countries

In the US, a diagnosis of SAD was first proposed by Norman E. Rosenthal, M.D. in 1984. Rosenthal wondered why he became sluggish during the winter after moving from sunny South Africa to (cloudy in winter) New York. He started experimenting increasing exposure to artificial light, and found this made a difference. In Alaska it has been established that there is a SAD rate of 8.9%, and an even greater rate of 24.9% for subsyndromal SAD.

Around 20% of Irish people are affected by SAD, according to a survey conducted in 2007. The survey also shows women are more likely to be affected by SAD than men. An estimated 3% of the population in the Netherlands suffer from winter SAD.