Diagnosis and classification of affective disorders: new insights from clinical and laboratory approaches.

Distinctions among affective disorders are reviewed in the light of dexamethasone non-suppression (DST) and shortened REM latency. Against the background of clinical, genetic and pharmacological information, such procedures may help to clarify biological continuities and discontinuities which need to be incorporated into the classification of affective disorders, and their differentiation from border conditions. Normal loss reactions, anxiety and dysphoric states are distinguishable from primary depression on the basis of REM latency. The melancholias, which tend in addition to be DST positive, are set apart from other primary depressions. Psychotic unipolar and bipolar depressions are classed under melancholia, because they tend to be most deviant in terms of cortisol non-suppression. Yet the fact that REM latency is abbreviated in most primary depressions, irrespective of the presence of melancholic features, argues for combining the two groups within a single class. These considerations suggest that the distinctions among affective subtypes are both categorical and dimensional.