Reliability and validity of the symptoms of major depressive illness.

In two consecutive studies, we examined the interrater reliability and then the concurrent validity of interview ratings for individual symptoms of major depressive illness. The concurrent validity of symptoms was determined by assessing the degree to which symptoms observed or reported during an interview were observed in daily behavior. Results indicated that most signs and symptoms of major depression and melancholia can be reliably rated by clinicians during a semistructured interview. Ratings of observable symptoms (signs) assessed during the interview were valid indicators of dysfunction observed in daily behavior. Several but not all ratings based on patient report of symptoms were at variance with observation. These discordant patient-reported symptoms may have value as subjective reports but were not accurate descriptions of observed dysfunction.