Julia D. Grant1, Kathleen K. Bucholz1, Pamela A. F. Madden1, Wendy, S. Slutske2, & Andrew C. Heath 1.
Peer substance use is one of the best predictors of adolescent alcohol and drug use. However, little attention has been paid to how an adolescent becomes involved with peers who drink alcohol, smoke, or use other illicit drugs. In the present analyses, we explored two issues surrounding peer substance use: what is the extent of genetic influence on and what adolescent characteristics are predictive of having peers who use illicit substances. Using data from the Missouri Adolescent Female Twin Study, we examined adolescents' responses to questions about whether their friends drank alcohol (did any friends, did most friends, and did their close friends), smoked cigarettes (same questions as with alcohol), had tried marijuana, or had tried other drugs. Data from 414 twin pairs (MZ=249; DZ=165), with a mean age of 18.2 years, were included. For all variables, polychoric correlations were consistent with substantial shared environmental influence: MZ correlations ranged from .66 to .88; DZ correlations ranged from .54 to .84. Logistic regression analyses were used to assess the significance of genetic effects and to examine which adolescent characteristics were predictive of having peers who had tried illicit substances. Although the MZ twins tended to have somewhat larger odds ratios than the DZ twins (consistent with the hypothesis of a genetic influence), in no case was the difference statistically significant. Additional logistic regression analyses indicated that conduct problems were the adolescent characteristic most likely to predict peer substance use. Furthermore, for depression (DSM-iv) and having older peers, if at least one member of the twin pair met the criterion then the pair was at increased risk for having peers who had used illicit substances.
Address: Department of Psychiatry, Washington University School of Medicine, 40 N., Kingshighway, Suite 1, St. Louis, MO 63108, Phone: (314) 286-2299, Fax: (314) 286-2213, Email: julie@matlock.wustl.edu
1Department of Psychiatry, Washington University School of Medicine, 40 N. Kingshighway, Suite 1, St. Louis, MO 63108 2University of Missouri, Columbia, MO 3Supported by AA09022, AA07728, DA07261, DA00272.