We measured alcohol problems using a factor score that included ten items from the Alcohol Use Disorders Identification Test (AUDIT) [26], seven DSM-IV Alcohol Dependence criteria [27], and three additional measures related to alcohol problems (getting into fights, police involvement, and drinking to alleviate withdrawal symptoms) that were collected as part of the age 18 assessment. To increase our sample size, we also imputed age 18 alcohol problems data for the participants who completed the age 16 alcohol assessment, but not the age 18 assessment (n = 1993) using imputation software IVEware [28]. Frequency and correlation checks after imputation showed that all imputations kept similar frequency distributions and that imputed and original variables were closely correlated. The results of an exploratory factor analyses indicated one main factor (eigenvalue = 6.78) that broadly measured heavy alcohol use and problems. We then ran a confirmatory factor analysis to calculate factor scores using Mplus 6.11 [29]. All items’ factor loadings were >0.30, and the items with the greatest loadings were: frequency of heavy drinking (6 or more drinks on one occasion); drinks per
