Nosology of chronic mood disorders.

In attempting to assess the complex relationship of chronic depression with other conditions to which it may be a predisposition, an accompaniment, or a consequence of, a few concluding caveats may be useful. It must be recognized that chronic depression has a wide variety of different presentations and causes. Current definitions of major depressive disorder and dysthymic disorder may create a misleading distinction of what may be two aspects of the overall course of a depressive disorder. Furthermore, much of what is considered to be comorbidity of other disorders with chronic depression actually may be a complex syndrome with a common pathogenesis.