Average levels of alcohol use and heavy drinking increased from age 17 to age 24 and then decreased. Friends' alcohol use decreased throughout adulthood (Table 2). Correlations between alcohol use and heavy drinking within each wave ranged from .47 to .79 (all p<.001), with lower correlations at older ages. At each wave, friends' alcohol use was positively related to own alcohol use and heavy drinking (r = .18 to .45, all p<.001). DRD4 was not correlated with alcohol use, heavy drinking, or friends' alcohol use at any wave.
