Mood disorders in the general population represent an important and worldwide public health problem.

There are now credible empirical data to support the conclusions that depressive disorders are among the most common diseases that human beings experience, with approximately 11.3% of all adults afflicted by these disorders during any one year. In comparison to common medical illnesses, such as diabetes, hypertension, lung diseases, etc., depression is associated with significantly greater physical limitations, more dysfunction in ability to perform one's social and occupational role and with increased bed days and poorer estimation of personal health. The disability associated with depression is compounded and extended by the fact that depressive disorders have a high tendency toward recurrence, relapse and chronicity. Thus, not only are patients acutely disabled from acute episodes of major depression or dysthymia, but they tend to be disabled for significant segments of their lifetimes by the lifelong nature of the clinical course of the mood disorders. Further, the scientific evidence now available indicates that even subsyndromal symptomatic and minor depressions are associated with significant disability and dysfunction as well. Finally, the accumulation of high prevalence, the significant disability and the lifelong nature of depressive disorders results in a palpable impact on all of the national economies throughout the world. It can be confidently concluded that depressive disorders are among the most common, disabling and costly of any of the diseases in the health care spectrum and represent significant, serious public health problems.