Abstract
AIMS: To test whether drinking onset moderates genetic and environmental contributions to individual differences in the etiology of alcohol expectancies across adolescence. DESIGN: Longitudinal twin design. SETTING: Community sample from Los Angeles, CA, USA. PARTICIPANTS: A total of 1292 male and female twins, aged 11–18years, were assessed at 1 (n = 440), 2 (n = 587) or 3 (n = 265) occasions as part of the risk factors for the Antisocial Behavior Twin Study. MEASUREMENTS: Social behavioral (SB) alcohol expectancies were measured using an abbreviated version of the Social Behavioral subscale from the Alcohol Expectancy Questionnaire for adolescents (AEQ-A). Drinking onset was defined as >1 full drink of alcohol. FINDINGS: Alcohol expectancies increased over age and the increase became more rapid following onset of drinking. The importance of genetic and environmental influences on SB scores varied with age and drinking status, such that variation prior to drinking onset was attributed solely to environmental influences, whereas all post-onset variation was attributed to genetic influences. Results did not differ significantly by sex. CONCLUSION: Only environmental factors explain beliefs about the social and behavioral consequences of alcohol use prior to drinking onset,whereas genetic factors explain an increasing proportion of the variance in these beliefs after drinking onset.