Depression is highly prevalent. Community surveys in 14 countries have estimated that the lifetime prevalence of unipolar depressive disorders is 12 percent . In patients with general medical illnesses such as diabetes or coronary heart disease, the prevalence of major depression is estimated at 10 to 20 percent .
In addition, disability due to depression is common. The World Health Organization ranks unipolar major depression as the 11th greatest cause of disability and mortality in the world, among 291 diseases and causes of injury . In the United States, major depression ranks second among all diseases and injuries as a cause of disability, and dysthymia ranks 20th .
Major depression is also highly recurrent. Following recovery from one episode, the estimated rate of recurrence over two years is greater than 40 percent; after two episodes, the risk of recurrence within five years is approximately 75 percent .
This topic reviews the efficacy of standard therapies for the initial treatment of depression in primary care patients and in patients with general medical illnesses. The choice of therapy for the initial treatment of depression and the general evidence of efficacy of standard therapies are discussed separately, as are the general principles and prognosis for the initial treatment of depression, and the evidence for therapies that are not typically used. Continuation and maintenance treatment of major depression, the treatment of resistant depression and refractory depression, and the clinical manifestations and diagnosis of depression are also discussed elsewhere.
●(See "Unipolar major depression in adults: Choosing initial treatment".)