Familial influences on alcohol use in adolescent female twins: testing for genetic and environmental interactions.

OBJECTIVE: Both genetic and common environmental influences contribute to twin associations for substance use; however, twin concordance rates may vary by environmental setting, indicating the presence of genetic-environmental interactions. The present study examined whether measures of family adaptability and cohesion may moderate the genetic influence on risk for alcohol use among female adolescents.
METHOD: We examined such interactions through the application of log-linear models using data from the Virginia Twin Study of Adolescent Behavioral Development, a longitudinal study with extensive home interviews of adolescent (8-17 year old) female twins (386 monozygotic [MZ] pairs, 185 dizygotic [DZ] pairs) and their parents.
RESULTS: Twin concordance for alcohol use varied by average twin/parent reports of parental closeness. Differences between MZ-DZ correlations for alcohol use in families with low parental closeness, for example, were 0.97 and 0.67 (p < .001), respectively, compared with 0.79 and 0.73 (p = .24) for high parental closeness families. In addition, differences in twin concordance regardless of zygosity were found with greater twin similarities for alcohol use in strict families compared with leniently disciplined families, suggesting that the twin association interacts with common environmental influences on alcohol use.
CONCLUSIONS: These results indicate that the genetic effects on adolescent alcohol use interact with the measured family environment and that the heritability of alcohol use may vary according to quality of the parental relationship. If confirmed, prevention programs may benefit from this knowledge, tailoring their intervention to quality of parental relationship.