External validating criteria for psychiatric diagnosis: their application in affective disorders.

Recent advances in biological psychiatry have provided the field with a raison d'être as a unique branch of psychological medicine. Many clinicians are understandably skeptical about the application of such biological techniques in improving the art of clinical diagnosis in psychiatry; most claims for the specificity of biological markers for a given nosological entity have not been replicated. Although much work lies ahead of us, methodological and research findings summarized in this review suggest that certain biological markers are beginning to provide external validating criteria for many psychiatric disorders, especially in the diagnosis of affective illness. Indeed, the rationale and validity of these markers rests on more solid basis than such routine "tests" as proverb interpretation, the Roschach and projective methods in general!