Prevalence and Risk Factors

Major depressive disorder is among the most common psychiatric syndromes affecting approximately one in four American women and one in ten American men during their lifetimes. Although the overall prevalence rates have stabilized, the average age of onset for the disorder has decidedly decreased. Numerous risk factors for depression have been identified and are listed in Table 3.3. 

Female gender Prior history of depression Family history of depression Active substance abuse Recent stressful life event Poor social supports Previous suicide attempt Postpartum period Chronic medical illness 

Patients with depression usually do not present initially to mental health professionals. Most visit their primary care physicians, complaining not of depressed mood but of other symptoms of depression. Fatigue, insomnia, loss of appetite, loss of interest in sex, muscle tension, body aches, and poor concentration are all commonly reported. These so-called masked presentations of depression may in part explain the documented failure of primary care physicians to diagnose depression reliably. This underscores the importance of considering depression in the differential diagnosis of physical complaints that appear vague or exaggerated. 

The long-term course of MDD is highly variable but in approximately half of patients evolves into a chronic, relapsing illness. Untreated, a major depressive episode typically lasts about 6-12 months before resolving spontaneously. The emotional, physical, and social toll exacted during these months of depression can be tremendous. When the illness remits, most patients are able to function at their previous level however, 20% experience only a partial remission with persistent depressive symptoms that may last months or even years. 

There is unfortunately no reliable means to predict which patients suffering from a first episode of depression will have relapses of illness. Of the patients who experience an initial major depressive episode, approximately 50-60% will have a second depressive episode. Of those, 65-75% will experience a third episode of the illness. Once a third episode has occurred, the chances of a fourth are 85-95%. Although 

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