At baseline, participants from case families averaged about 16 years of age, with those from comparison families about 1 year younger. Evidence of having initiated substance use was abundant, and more common among those from case versus comparison families, across all types of substances. Alcohol was the most commonly used substance, with about 50% of those in case, compared with about 30% of those in comparison, families reporting ever having a drink. The most common substance use disorders were Alcohol and Cannabis dependence, with higher prevalence of both among participants from case versus comparison families; 4.2% and 6.8% of case family participants, compared with 1.4% and 2% of comparison family members, met diagnostic criteria for alcohol and cannabis dependence, respectively. Likewise, prevalence estimates of non‐substance externalizing disorders (Conduct Disorder, ADHD, and ODD) were higher among participants from case families compared with their counterparts from comparison families.
