Study limitations are noted. As with all substance abuse studies, information is vulnerable to self-report bias and biological tests or informant reports were not obtained. However, since self-reported substance use tends to be accurate in the absence of sanctions (Magura et al., 1987), and since the patients reported a high prevalence of the SUD criteria, we doubt that self-report bias influenced the results. In addition, all clinical settings were located in the greater New York metropolitan area. Studies with greater geographic distribution would also be important. For example, if the NIDA Clinical Trials Network could adopt standard assessment of all the DSM-5 SUD criteria among participants in all trials, then a great deal of important research could be conducted with the resulting data. Strengths of our study included reliable assessments administered in a standardized way by experienced clinicians, a relatively large sample in which four substances could be examined, and state-of-the-art statistical procedures.
