We note that two different structured instruments were used in establishing diagnosis, the SCID (two versions, for DSM-III-R and for DSM-IV) and the SSADDA. Strong cross-system agreement for substance use disorders as defined by DSM-III-R, DSM-IV and ICD-10 (the International Classification of Diseases, version 10) has been reported (39). Moreover, the SSADDA can yield reliable DSM-IV diagnoses for a variety of psychiatric disorders, including alcohol and drug dependence (26,40). Therefore, it is unlikely that multiple measures applied in this study led to significant phenotypic heterogeneities.
