Hser, Y. I., Grella, C. E., Collins, C., and Teruya, C. (2003).  Drug use initiation and conduct disorder among adolescents in drug treatment.  Journal of Adolescence, 26(3), 331-345.

Abstract:  This study investigated effects of drug-use initiation and conduct disorder (CD) among 1031 adolescents who participated in the Drug Abuse Treatment Outcomes Studies for Adolescents (DATOS-A) sponsored by the National Institute on Drug Abuse (NIDA).  The mean age of first drug use was 12.7 (S.D.=2.2), 570/0 met DSM-III-R criteria for CD, and earlier initiators were more likely to have CD.  About 78% of the adolescents with CD reported that their first CD symptom occurred prior to drug-use initiation.  The proportions of adolescents who had prior treatment were similar (about 28%) across all groups, but earlier initiators reported a greater number of treatment episodes and younger ages at their first treatment.  Conduct disordered adolescents revealed greater problems prior to DATOS-A treatment, but they appeared to be more motivated and ready for treatment.  Although adolescents with CD still showed worse outcomes after treatment, the impact of CD appeared to lessen when pretreatment differences were controlled.  To a lesser extent, adolescents who began using drugs at earlier ages had greater alcohol and drug use and other problems at intake, but their treatment outcomes appeared to be similar to later initiators.  There were few significant interaction effects of initiation and CD.  Findings from this study highlight the importance of better understanding the progression of drug use, treatment utilization, and psychiatric comorbidity among adolescents with substance abuse problems.