The link between family history and early onset alcoholism: earlier initiation of drinking or more rapid development of dependence?

OBJECTIVE: This study examines the association between early onset alcoholism and family history to determine whether family history of alcoholism is predictive of earlier initiation of drinking, more rapid onset of dependence once drinking has begun, or both.
METHOD: Using cross-sectional, retrospective data from a large, nationally representative sample of U.S. adults, discrete time proportional hazards models were used to assess the effects of family history saturation (% of alcoholic first- and second-degree relatives) on: ( 1) the risk of initiating drinking among all adults (N = 42,862; 58.4% female) and (2) the risk of progressing from initiation of drinking to onset of dependence among lifetime drinkers (n = 27,616; 50.7% male). Models were estimated for different time periods, to see if the effect of family history saturation varied over time in a manner suggestive of a stronger association with early onset dependence.
RESULTS: The positive effect of family history saturation on the risk of initiating drinking was strongest prior to age 15 and declined steadily with increasing age. It was slightly weaker for men than women. After controlling for early initiation of drinking, the direct positive effect of family history saturation on the risk of progressing to dependence increased over time and was slightly reduced among individuals who started drinking before age 18. The indirect effect of family history on the risk of developing dependence, via its effect on early drinking as a risk factor for dependence, was strongest in the interval from 3 to 9 years after initiation of drinking.
CONCLUSIONS: The association between family history and early onset alcoholism appears to be driven most clearly by family history predicting earlier initiation of drinking. The weak effect of family history on the development of dependence within the first 3 years after initiation of drinking may reflect the preponderance of developmentally limited dependence during this time period. The data are consistent with the links established between novelty seeking, impulsivity and early onset alcoholism. While supporting the possibility of genetic effects via dopaminergic and serotonergic function, these findings also suggest that environmental factors may play an important part in helping to explain the association between family history and early onset alcoholism.