In general, linkage found in the current study was stronger when the dataset maximised data collected at a younger age, as was the case for peaks on 1p and 6p for Quantity × Frequency. This supported the proposal that the trend for heavier drinking among younger individuals could enhance linkage for consumption. However, peaks found on 3q (Quantity) and 5q (Frequency) were maximal for the dataset maximising data collected at an older age. These results suggest that factors under genetic control, which influence drinking habits, may change as people age, although previous analyses suggest that heritability itself is stable over periods of approximately 5 to 10 years (Hansell et al., 2008). Nonetheless, our earlier analyses also showed consumption to be less heritable in a younger versus older cohort (23–39 years vs. 28–90 years), consistent with other findings (Carmelli et al., 1993), and consistent with the view that environmental and genetic influences on consumption may change over time.
