Close friend substance use was additionally assessed from the Important People and Activities (IPA) questionnaire (Longabaugh et al., 1995). Since the IPA was administered to a subset of the COGA Prospective Study sample (210 out of 412 in the genotypic sample), analyses involving the IPA were included as secondary analyses. Participants were asked to name at least four “important people” in their lives (excluding relatives, but including siblings), and then rate the frequency of that person’s alcohol use on a 0 to 7 scale. A score was computed by the average of the frequency of alcohol use among each of the important individuals listed by the participant. Baseline data were used.
