Under the best-fitting model, heritable influences accounted for a substantial proportion of the variance in the timing of first alcohol use (36%) and an even larger proportion of the variance in AD status (53%). There was also a considerable degree of overlap in these genetic factors (rA1-A2 = 0.59; CI: 0.45-0.80). The timing of alcohol use initiation was attributable in small part to shared environmental factors (15%), but there was no evidence that shared environment played a role in the development of AD.
