Subclinical externalizing behavior, impulsivity-related traits, parental monitoring, and perceived peer substance use data came from prospective participants' first assessment of these constructs [adolescents: age = 14.44 years (SD = 1.78; range 12-17 years), n = 248 (54% male); young adults: age= 19.86 years (SD = 1.41; range 18-24 years), n = 207, (47% male)]. We note that parental monitoring and peer substance use data were available for adolescent prospective participants only. Owing to the longitudinal design of the Prospective Study, prospective participants have completed the externalizing disorders psychiatric interview multiple times. We used data from the interview where they endorsed the greatest number of alcohol dependence criteria to create the externalizing disorder composite, and we note that the mean ages at which these groups completed their psychiatric interviews were 16.74 (SD = 1.87) and 21.63 (SD = 2.95), respectively. Our scientific rationale for using externalizing disorder data from a single interview (versus calculating average scores across multiple assessments) was that in a high-risk sample such as COGA we wanted to measure individuals' greatest expression of their predisposition to the externalizing disorder (i.e., alcohol dependence) on which the sample was originally ascertained.
