This surprisingly strong association suggests that alcohol-related experiences in adolescence may have persistent effects on alcohol and substance use patterns, even into middle adulthood. However, the MLDA effects do not seem to be working through age of drinking initiation: although MLDA exposures did predict age of onset of regular and weekly drinking, the effect estimates for alcohol and substance use disorders were little changed in regression models that also included lifetime abstention status and age of initiation, and were similar and separately significant among subjects who had already started to drink by the age of 16 and among those who had not. Although age of onset may indeed be a causal risk factor for later substance use disorders, these results suggest that the long-term effects of MLDA exposures on harmful drinking may work through other aspects of late adolescent drinking, such as the intensity or patterning of drinking.. This ‘drinking pattern’ hypothesis is consistent with the many studies finding that more restrictive purchase ages do reduce the frequency and intensity of alcohol use among underage drinkers, even though underage drinking
