Age at regular alcohol use: Answer options: <11 years, 12, 13, 14, 15, 16, 17, 18 years or older, never (survey 2,3,4,8). When longitudinal data were available (also for age first cannabis): with a discrepancy of 1 or 2 years, the youngest age is selected, with a discrepancy of more than 2 years, the variable is set to missing 0–5% of cases).
