Feelings of sadness, hopelessness, and a loss of interest in life, combined with a sense of reduced emotional well-being. Symptoms vary with the severity of the depression. It may cause loss of appetite, difficulty in sleeping, tiredness, loss of interest in social activities, concentration problems, and, sometimes, anxiety. The severely depressed may have thoughts of suicide and feelings of worthlessness. Hallucinations or delusions may occur in extreme cases. Often, there is no single obvious cause. It may be triggered by physical illnesses (such as a viral infection), hormonal disorders (such as hypothyroidism), or hormonal changes after childbirth (see postnatal depression). Some drugs, such as oral contraceptives, may contribute. Inheritance may play a part. Some people become depressed in winter (see seasonal affective disorder syndrome). Aside from these causes, social and psychological factors may play a part. Treatment usually includes a form of psychological treatment, such as cognitive–behavioural therapy or counselling and/or antidepressant drugs. Antidepressant drugs are usually effective over a period of time. ECT (electroconvulsive therapy) is infrequently used for treating severely depressed people who have not responded to other treatments.


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