Problems in the classification of affective disorders.

Some of the concepts which have figured prominently in recent studies of the classification of affective disorders are examined. The include the "primary-secondary", the "bipolar--unipolar" and the depression/anxiety dichotomy. The problems posed by these three principles are closely entwined with one another. Inconsistencies in diagnosis will arise from the application of these principles until a broad consensus has been achieved regarding the nature of the relationship between "vital" or "endogenous" depression and other disorders of affect. Allocation into one of these two broad categories has to be made prior to all other diagnostic decisions within the field on affective disorder. Hence differences in the classification and nomenclature of emotional illness between the United States and European countries will cause groups of patients comprising "unipolar", "primary" and "secondary" disorders to differ in composition until divergent viewpoints have been resolved. There is a hierarchial order implicit in the Kraepelinian system of classification which should be made more explicit; it would foster standardisation and consistency in diagnostic practice. But the order of precedence should be regarded as a set of hypotheses rather than fixed rules. Some recent observations regarding schizo-affective and schizomanic disorders have refused one of these hypotheses and so refined knowledge.