Age at initiation of alcohol use was assessed by asking, “How old were you the first time you had more than just a sip of beer, wine, or spirits?” Mean age at first drink was 16.2 years for females and 15.4 years for males. In order to account for the potential skewness in its continuous form, a categorical variable representing age at first drink was created based on the distribution of age at initiation for males and females in combination. Those falling within the lowest 20% in the age range, 14 years and younger, (15.2% of females and 28.3% of males) were labeled “early” and those in the highest 20%, 18 years or older, (25.8% of females and 15.0% of males) were labeled “late.” Average age at first drink was defined as 15-17 years (representing 59.0% of females and 56.8% of males). Lifetime alcohol dependence (AD) was defined as endorsing full DSM-IV diagnostic criteria for the disorder (i.e., 3 or more of the 7 possible symptoms clustering in a 12 month period of time). A total of 15.0% of females and 30.4% of males met AD criteria.
