Clinical implications of "subthreshold" depressive symptoms.

There is active debate regarding whether diagnosable depression exists on a continuum with subthreshold depressive symptoms or represents a categorically distinct phenomenon. To address this question, multiple indexes of dysfunction (psychosocial difficulties, mental health treatment history, and future incidence of major depression and substance abuse/dependence) were examined as a function of the extent of depressive symptoms in 3 large community samples (adolescent, adult, and older adult; N = 3,003). Increasing levels of depressive symptoms were associated with increasing levels of psychosocial dysfunction and incidence of major depression and substance use disorders. These findings suggest that (a) the clinical significance of depressive symptoms does not depend on crossing the major depressive diagnostic threshold and (b) depression may best be conceptualized as a continuum. Limitations of the present study are discussed.