The study of depressive disorders using the PSE-ID-CATEGO system.

The PSE-CATEGO-ID system and its approach to the sub-classification of depression is described. The principle of sub-classification partly corresponds to the empirical relationships between symptoms on affective disorder. Comparison of CATEGO and DSM III demonstrates that major differences of classification can arise because of differences of the classificatory algorithm even though similar lists of symptoms are used. Empirical studies of the PSE-CATEGORO-ID system are described and their importance in providing evidence for a rational choice between classificatory system is emphasised.