An alcohol use index (AUI) was derived from five measures: frequency of drinking occasions, average number of drinks per occasion, frequency of intoxication, and symptoms of alcohol abuse and dependence. An expanded version of the Substance Abuse Module of the Composite International Diagnostic Interview26 was used to assess alcohol abuse and dependence symptoms. The AUI was composed by setting scores on these five variables on a 0–10 scale and then averaging them. This index is essentially equivalent to a latent variable approach: a factor analysis with all five alcohol measures modeled as indicators of a single latent alcohol use variable had high factor loadings (range .81–.89 across indicators) and explained 70% of their variance. This latent alcohol use variable was very highly correlated with the AUI at all ages, ranging from .98 (age 14) to .99 (ages 17, 20, 24, and 29). However, a latent variable could not be calculated for age 11 because participants have not begun drinking and there is no variance in use. In contrast, the AUI yields a single manifest variable with a meaningful “0” point
