Causes of Mood Disorders

Mood disorders are sometimes called affective disorders. Affect (emphasis on the first syllable) means emotional state as revealed through facial expressions and gestures.

Sadness and joy are part of the normal experience of everyday life and differ from the depression and mania that characterise mood disorders.

Sadness is a natural response to loss, defeat, disappointment, trauma, or catastrophe.

Grief or bereavement is the most common of the normal reactions to a loss or separation, such as the death of a loved one, divorce, or romantic disappointment.

Usually, bereavement and loss do not cause persistent, incapacitating depression except in people predisposed to mood disorders.

Causes of Depression

The exact cause of depression is unclear, but a number of factors may make depression more likely.

Risk factors include

  • A family tendency (heredity);
  • Emotionally distressing events, particularly those involving a loss;
  • Female sex, possibly involving changes in hormone levels;
  • Certain physical disorders; and
  • Side effects of certain drugs.

Depression does not reflect a weakness of character and may not reflect a personality disorder, childhood trauma, or poor parenting. Social class, race, and culture do not appear to affect the chance that individuals will experience depression during their lifetime.

Genetic factors contribute to depression in about half the individuals who have it. For example, depression is more common among first-degree relatives (particularly in an identical twin) of individuals with depression. Genetic factors can affect the function of substances that help nerve cells communicate (neurotransmitters). Serotonin, dopamine, and norepinephrine are neurotransmitters that may be involved in depression.

Women are more likely than men to experience depression, although the reasons are not entirely clear. Of physical factors, hormones are the ones most involved. Changes in hormone levels can cause mood changes shortly before menstruation (as part of premenstrual syndrome), during pregnancy, and after childbirth. Some women become depressed during pregnancy or during the first 4 weeks after giving birth (called baby blues or, if the depression is more serious, postpartum depression). Abnormal thyroid function, which is fairly common among women, may also be a factor.

Depression may occur with or be caused by a number of physical disorders and factors. Physical disorders may cause depression directly (as when a thyroid disorder affects hormone levels) or indirectly (as when rheumatoid arthritis causes pain and disability). Often, a physical disorder both directly and indirectly causes depression. For example, AIDS may cause depression directly if the human immunodeficiency virus (HIV), which causes AIDS, damages the brain. AIDS may cause depression indirectly by having an overall negative effect on the individual’s life. Many individuals report feeling sadder in late autumn and winter and blame this tendency on the shortening of daylight hours and colder temperatures. However, in some individuals, such sadness is severe enough to be considered a type of depression (called seasonal affective disorder).

The use of some prescription drugs, such as some beta-blockers (used to treat high blood pressure), can cause depression. For unknown reasons, corticosteroids often cause depression when the body produces them in large amounts as part of a disorder (as in Cushing syndrome), but when they are given as a drug, they tend to cause hypomania (a less severe form of mania) or, rarely, mania. Sometimes stopping a drug can cause temporary depression.

A number of mental health disorders can predispose an individual to depression. They include certain anxiety disorders, alcoholism, other substance use disorders, and schizophrenia. Individuals who have had depression are more likely to have it again.

Emotionally distressing events, such as loss of a loved one, can sometimes trigger depression, but usually only in people who predisposed to depression, such as those who have family members with depression. However, depression may arise or worsen without any apparent or significant life stresses.

Causes of Bipolar Disorder

The exact cause of bipolar disorder is not known.

Heredity is thought to be involved in the development of bipolar disorder. Also, certain substances the body produces, such as the neurotransmitters norepinephrine or serotonin, may not be regulated normally (Neurotransmitters are substances that nerve cells use to communicate.).

Bipolar disorder sometimes begins after a stressful event, or such an event triggers another episode. However, no cause-and-effect relationship has been proved.

The symptoms of bipolar disorder – depression and mania – can occur in certain disorders, such as high levels of thyroid hormone (hyperthyroidism).

Also, episodes may be triggered by drugs, such as cocaine and amphetamines.

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