Prevalence and clinical course of depression: a review.

Depression is one of the leading causes of disease worldwide. Historically conceived as either a disease of the mind or of the brain, treatment options followed this aetiology. Current diagnostic assessment of depression is based on descriptions of symptoms, their presence and magnitude over time. Epidemiological studies demonstrate that depressive disorders are highly prevalent: displaying high rates of lifetime incidence, early age onset, high chronicity, and role impairment. These studies have deepened our understanding of the course of depression; remission, recovery, relapse and recurrence. An illustration of recovery rates has begun to demonstrate the complexity of the nature and course of depression. The majority recovers; however, recovery may not be permanent and future episodes carry the threat of chronicity. A key variable influencing rates of recovery, relapse, and recurrence is the presence of medical or psychiatric comorbid illnesses. The review considers the literature on Major Depression beginning with a brief historical overview, its classification, and a synthesis of the current knowledge regarding prevalence and course.