behavior from early adolescence to adulthood, while 17% of the sample showed consistent elevated levels of externalizing behavior that persisted into adulthood. The individuals showing this pattern of persistently high externalizing behavior were significantly more likely to carry the variant of GABRA2 that was originally associated with increased risk for adult alcohol dependence in the COGA sample13 (though we note that there is inconsistency as to the risk allele across studies).39 Our findings extend the association with GABRA2 to a nonselected community-based sample, confirm broad-based involvement in general externalizing behavior, and demonstrate that this gene is associated not only cross-sectionally with behavioral outcome, but with different trajectories of behavior extending from adolescence to young adulthood.
