In the COGA adolescent and young adult study, 2,580 individuals with a first interview age of 12 to 22 were genotyped for the ADH1B rs1229984 variant, and participants for the analyses were drawn from this group (Figure 1). Focusing on European and African American subjects and excluding individuals with missing or unreliable data left 2,410 individuals (entire sample described in Table 1). The samples used for the primary analyses of first intoxication and first DSM-5 symptom consisted of 1,550 ever-drinkers before age 18 (also described in Table 1). Ever-drinkers were targeted because the ADH1B variant is only expected to exhibit a protective effect in response to alcohol consumption. Because the peer drinking variable examined the age-range of 12-17, the primary analyses focused on events that occurred during this time.
