Depression - in psychiatry, a symptom of mood disorder characterized by intense feelings of loss, sadness, hopelessness, failure, and rejection. The two major types of mood disorder are unipolar disorder, also called major depression, and bipolar disorder, whose sufferers are termed manic-depressive (see manic-depressive disorder). Other types of depression are recognized, with characteristics similar to the major mood disorders, but not as severe: they are adjustment disorder with depression, dysthymic disorder, and cyclothymic disorder.

Close to 20% of Americans are likely to suffer major depression at some time, and women tend to be more susceptible to the disorder than men. Major depression is likely to interfere significantly with everyday activity, with symptoms including insomnia, irritability, weight loss, and a lack of interest in outside events. The disorder may last several months or longer—and may recur—but it is generally reversible in the short run.

Bipolar disorder is much rarer, affecting only about 1% of the U.S. population; women and men tend to be equally susceptible. Its sufferers alternate between states of depression—similar to that which is experienced in unipolar disorder—and mania, which is characterized by intense euphoria and frenetic activity. Bipolar disorders are often interspersed with periods of relatively normal behavior, which may last for long periods of time between episodes of depression or mania. Manic-depressives have an extremely high rate of suicide, and episodes of the disorder tend to recur.

Medical evidence suggests that depressive states may be connected to deficiencies in the neurotransmitters norepinephrine and serotonin. Drug therapy includes various antidepressants that act on the flow of neurotransmitters and lithium for bipolar disorder (antidepressants can cause mania when used to treat depression in bipolar patients). There also has been success with electroconvulsive therapy (ECT) for major depression.

In recent years, theorists have argued that many depressed individuals depend upon others for their self-esteem, and that the loss of one of these emotional supports often precipitates a depressive reaction. A number of psychologists contend instead that depression is a result of learned helplessness, which occurs when a person determines through experience that his actions are useless in making positive changes. Other theorists have shown that genetic factors play a major role in depression.

See L. Wolpert, Malignant Madness (2000).

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