The subjects were interviewed using the Lifetime History of Alcohol Use and Lifetime Drug Use History surveys (Center for Education and Drug Abuse Research, 1989a, 1989b) at each follow-up evaluation to document chronological age when alcohol and cannabis were consumed for the first time. The mean age of first alcohol and cannabis use was, respectively, 178.00 months (SD = 25.03) and 191.17 months (SD = 28.64), or 14.8 and 15.9 years, respectively, after birth.
