Toward the integration of classification theory and methods.

Although various criteria have been proposed for the evaluation of psychiatric classifications, there is need for an integrated paradigm. This article presents such a framework based on the principles of construct validation. Emphasis is placed on the continual interplay between theory development and empirical analyses. First, the theory formulation component involves specification of the theoretical types and their functional linkages. Then, the internal validation component entails development of an empirical typology followed by an evaluation of its reliability, coverage, homogeneity, and robustness. Finally, the external validation component evaluates predictive validity with respect to treatment outcome, clinical meaningfulness of the diagnostic categories, descriptive validity, and generalizability of the typology to other populations. This framework is used to evaluate (a) the new diagnostic system (Diagnostic and Statistical Manual of Mental Disorders-Ill) developed by the American Psychiatric Association, (b) recent classifications of psychopathology that were derived using empirical clustering methods, and (c) classifications of behavioral disorders that have an explicit theoretical basis. A key challenge for the scientific understanding of abnormal behavior is to achieve a synergism between theory formulation and empirical classification methods. The history of psychiatric classification has been marked by sporadic periods of great activity. Recently, several developments have fueled a renewed interest in classifying mental and behavioral disorders. These include publication of a new diagnostic system (Diagnostic