In Dutch samples of treated heroin addicts, high prevalences of a heterogeneous psychiatric co-morbidity can be found with regard to Diagnostic and Statistical Manual (third edition) (DSM-III) classifications, Zung Depression Inventory, and sum scores of a 90-item Symptom Checklist (SCL-90). A high-threshold (N = 87) and a low-threshold (N = 116) program are compared with regard to psychopathology and severity of psychopathology. A consecutive admissions design was used. More than 50% of the respondents suffered from a lifetime DSM-III Axis I disorder (70% with antisocial personality disorder included), and 40% were still suffering from one of the disorders in the year preceding the interview. Schizophrenia was diagnosed five times as much as in normal population samples (5%). The most frequently diagnosed disorders were recurrent major depression, phobic disorders, alcohol abuse and dependence, dysthymic disorder, and antisocial personality disorder. The prevalences of DSM-III disorders, the total number of symptoms, and the score on the Zung Depression Inventory and 90-item Symptom Checklist were all significantly higher in treatment-seeking drug addicts entering the high-threshold program. Within each program, three clinically meaningful subgroups can be distinguished: one group with DSM-III Axis I lifetime or current psychopathology and/or antisocial personality disorder, one with antisocial Personality disorder only, and one with neither DSM-III psychopathology nor antisocial personality disorder. Possibly, self-selection results in patients with more serious conditions entering more treatment-oriented facilities. Odds ratios show that schizophrenia and mood disorders and especially associated on a lifetime and current basis.
