Using a more stringent definition of early use (use prior to age 17) also did not alter the results. When the 176 early-using (before age 17) “cases” were compared to their later/never-using cotwins, the early users were at significantly increased risk of stimulant use, hallucinogen/PCP use, use of any illegal drug other than cannabis, and alcohol dependence (ORs: 2.18-3.30). Only alcohol dependence remained significant when the 130 early-users were compared to their later-using cotwins (OR=2.13).
