Substance abuse/mental illness: diagnostic issues.

"Dual diagnoses" of substance abuse and mental illness disorders are common both in psychiatric and substance abuse treatment settings. Recent studies have demonstrated that specific diagnostic categories of mental illness have implications for treatment outcomes of dually disordered patients, but a diagnostic standard has not emerged. The present study compared lay-administered DIS diagnoses with clinical diagnoses of patients in a state hospital treatment program for "dual diagnoses" patients. Categories of DIS diagnoses showed weak association with categories of clinical diagnoses. Several frequent DIS diagnoses were not made clinically and vice versa. Implications for choice of diagnostic instruments to use with this patient population are discussed, as is the potential value of structured assessments in supplementing clinical data.