There has been inconsistency in the genetic model associated with GABRA2 in different studies and in different age groups (Dick, Bierut et al. 2006); accordingly, we coded the genotypes so as to not assume a specific genetic model. In these analyses, we found a greater jump in drunkenness during the transition from adolescence to adulthood among individuals carrying 0 copies of the minor allele, with no difference observed among individuals heterozygous or homozygous for the minor allele. This is the same genetic model (risk associated with carrying 0 copies of the minor allele, alternately referred to as two copies of the major allele) that was associated with elevated alcohol problems in our previous cross-sectional studies of adults. In other words, the genotype originally associated with adult alcohol dependence in the parental generation of COGA is the same genotype associated with the sharper increase in drunkenness from 18 to 19 found among these prospectively followed children of COGA families.
