Table 2a summarizes the characteristics of each of the latent classes and Table 2b provides summary statistics for the DSM-IV criteria for each latent class. As expected, there were significantly more DSM-IV AD individuals (X2=1222.3, df=2, p<0.0001) and significantly more males (X2=66.2, df=2, p<0.0001) in the moderate and high-risk classes. The mean number of DSM-IV criteria was significantly different among the three classes (overall F(6, 1779)=2043.7, p<0.0001; p<0.0001 for each pairwise comparison), with higher scores in the high-risk class, indicating that classes reflected a continuum of severity as indexed by number of DSM-IV criteria. There was a main effect of latent class for age at regular drinking onset (overall F(6,1779)=83.0, p<0.0001; latent class p<0.0001), and a marginal effect for age (overall F(6,1779)=2394.0, p<0.0001; latent class p=0.045). The low-risk class contained no individuals meeting criteria for AD, although some individuals endorsed tolerance (30%) or drink more than intended (28%). Individuals in this class began drinking regularly at a significantly older age (19.5 years) than those in the moderate (p<0.0001) or high-risk (p<0.0001) classes. In the moderate risk class, 66% were AD,
