Genetic influences on quantity of alcohol consumed by adolescents and young adults.

Objective: To examine genetic and environmental influences on drinking in a nationally representative study of genetically informative adolescents followed into young adulthood.

Method: The average quantity of alcohol used per drinking episode during the past year was analyzed in 4432 youth assessed during adolescence (mean age of 16) and then 1 and 6 years later. The variance of quantity of alcohol consumed was decomposed into three components: additive genetic (a2), shared environmental (c2), non-shared environmental (e2). Four candidate genes were tested for association.

Results: Wave 1 a2-0.52e2-0.48, Wave 2 a2-0.28e2-0.72, Wave 3 a2-0.30e2-0.70. Genetic correlations between Waves 1 and 2 were 0.85, Waves 1 and 3 were 0.34. The DAT1 440 allele was associated at Wave 1 (p=0.007). DRD2 TaqI A1/A2 was associated at Wave 3 (p=0.007). DRD4 and 5HTT were not associated. The DAT1 and DRD2 polymorphisms accounted for 3.1% and 2.0% of the variation, respectively.

Conclusion: Genetic influence on drinking behavior was common in adolescents longitudinally assessed 1 year apart, but was less correlated between these adolescents and their assessment as young adults at a subsequent time point. Polymorphisms in genes of the dopaminergic system appear to influence variation in drinking behavior.