Empirical validation of diagnostic similarities from a structural perspective.

In an effort to establish definitive patterns of patient variables for the diagnostic categories used by psychiatry, this study investigated the similarity between diagnostic classes as perceived by psychiatrists when evaluating patients from their own caseloads. A grid method was used to evaluate the diagnostic process. Thirteen psychiatrists rated their own patients on the constructs generated from their own personal dimensions. An overall analysis of the data demonstrated that patients within a diagnostic category were seen as more similar to one another than were patients from different diagnostic categories. Similarities between diagnostic classes showed that neurotic/situational maladjustment, personality disorder/alcoholic, and psychotic/alcoholic were the most similar pairs of unlike diagnoses. Examination of the process of diagnosis showed the functional similarity between some diagnostic classes. Specific areas of diagnostic similarity were present in a system that produced overall diagnostic clarity. Implications for the use of the grid method in psychiatric training were discussed.