Depression is one of the most common mental health conditions globally, affecting over 280 million people. It is also one of the most underdiagnosed because many people do not recognize that their physical symptoms — chronic fatigue, pain, sleep disturbance — may be manifestations of depression rather than separate medical conditions.
Core symptoms recognized by the DSM-5 diagnostic criteria include: persistent depressed mood most of the day, nearly every day; significantly diminished interest or pleasure in most activities (anhedonia); changes in appetite or weight (loss or gain of > 5% body weight in a month); insomnia or hypersomnia; psychomotor agitation or retardation; fatigue or loss of energy; feelings of worthlessness or excessive guilt; difficulty concentrating or making decisions; and recurrent thoughts of death or suicidal ideation. Five or more symptoms present for at least two weeks constitutes a major depressive episode.
Physical symptoms of depression are often prominent and may mask the mood disorder: medically unexplained pain (headaches, back pain, gastrointestinal complaints), extreme fatigue, changes in appetite and weight, and disrupted sleep. Somatic symptoms of depression are particularly common in cultures where expression of emotional distress is less accepted.
Highly effective treatments include: cognitive behavioral therapy (CBT) — with strong evidence for mild to moderate depression; antidepressant medications (SSRIs are first-line, typically showing effect after 2–4 weeks); combined therapy (medication + CBT outperforms either alone in moderate to severe depression); exercise (shown to reduce depression symptoms as effectively as antidepressants in mild to moderate cases); and for severe or treatment-resistant depression, electroconvulsive therapy (ECT) or transcranial magnetic stimulation (TMS).
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