The classification of depressive disorders. II. A review of historical and physiological classification studies.

A review of recent classification studies of depressive disorders based on historical data and physiological indices was made. It was found that historical variables, such as age of onset and family background, are potentially useful to distinguish depressive subgroups, although these groupings did not differentiate consistently unipolar from bipolar depressives. While the physiological indices do not support the present psychiatric nosology, single physical signs were found to differentiate subgroups within the effective disorders. The implications of these findings for a different research model were discussed.