Major depressive disorder: longitudinal symptomatic structure, relapse and recovery

Major depressive disorder: longitudinal symptomatic structure, relapse and recovery Major depressive disorder (MDD) is a very common, complex, chronic and often lifelong disease, which has worldwide public health importance.Until recently much of the scienti®c and clinical attention has focused on the more severe syndromal manifestation of the illness, major depressive episodes (MDE).However, detailed characterization of the course of illness between MDEs has shown that the clinical presentation of the illness is much more varied and pleomorphic than thought previously (1).For example, subsyndromal forms of the illness, labeled as `minor', `intermittent', `dysthymic', or `subthreshold' have been described, but the clinical relevance and the importance of these subthreshold conditions and their relationship to syndromal MDD has not been fully explored.Interest in this complex realm was stimulated by the early clinical studies of Akiskal et al. (2, 3) and that of Keller et al. (4), as well as the epidemiological work of Angst and Dobler-Mikola (5), and services research by Wells et al. (6).Cumulatively, these authors showed that subthreshold conditions often progressed to major episodes, that chronicity of depression was more prevalent than suspected previously, and that subthreshold symptoms were clinically relevant, being associated with signi®cant psychosocial impairment.