Danielle M. Dick1, Richard J. Rose1, J. Kaprio2, & R. J. Viken1
Age at menarche (AAM) correlates with differences in alcohol use among adolescent girls, with earlier maturing girls initiating alcohol use at an earlier age. The MMPI Pd Scale also correlates with substance use/abuse, with higher scores more indicative of problematic behavior. But AAM and Pd scores are associated with between-family differences (e.g., family composition, rural/urban residency), so a rigorous test of the relationship of AAM and Pd with early drinking requires a within-family analysis. We report data on AAM, the MMPI Pd Scale, and self-reported drinking from 1,902 16 year-old female twins from FinnTwin16. Significant correlations, across all 1,902 twin individuals, were found between AAM and Drinking (r = .156), and Pd and Drinking (-.323), and both AAM and Pd showed significant linear trends with drinking frequency. Nearly 3X as many early, as late, AAM girls report weekly drinking, while only half as many report infrequent drinking or abstinence. For Pd, results were more pronounced: nearly 7X as many girls with high Pd scores report weekly drinking, while only a third as many report infrequent drinking or abstinence. To test these results within twin pairs, we selected highly discordant DZ twin sisters (99 pairs discordant > 2 years for AAM, and 115 SSDZ pairs most discordant for Pd, mean intrapair difference = 10 items). Results: early maturing sisters more often reported more frequent drinking (p = .059), as did sisters with higher Pd scale scores (p = .003). Within AAM-discordant DZ pairs, there was no linear association of AAM with Pd, and, across the entire sample, AAM and Pd correlated negligibly (-.047). Twin correlations in our data indicate significant genetic variance in both AAM (rMZ = .77, rDZ = .36) and Pd Scale scores (rMZ = .60, rDZ = .34), and conventional univariate and bivariate modeling will test for genetic variance and covariance.
Address: ddick@indiana.edu, 812-855-9395 (ph), 812-855-4691 (fax)
1Department of Psychology, Indiana University, Bloomington, IN 47405-1301 2Department of Public Health, University of Helsinki, FIN-00014, Finland 3Supported by NIAAA (AA-08315, AA-00145) and the Finnish Academy of Science