Mean monthly alcohol consumption was quite low in epoch 1 (age 12–14 years) at 0.67 (S.E.=0.13) drinks per month; it increased rapidly across epoch 2 (mean=7.24, S.E.=0.55), epoch 3 (mean=38.04, S.E.=1.53) and epoch 4 (mean=39.55, S.E.=1.79), after which consumption decreased to a mean of approximately one drink per day in epoch 5 (mean=30.50, S.E.=1.50) and epoch 6 (mean=29.25, S.E.=1.96). All other statistics and analyses employed natural log-transformed versions of the consumption variables. Phenotypic correlations from one epoch to the immediately subsequent epoch were modest to high (r=0.51–0.86, see Appendix Table A1), and increased over time as the pattern of alcohol use stabilized.
