the scales for hyperactivity-impulsivity, aggression, and inattention may be used to form a factor for externalizing problem behaviors (Pulkkinen et al., 1999). For our analysis, we utilized the scale for hyperactivity-impulsivity (‘impulsivity’ below). Further, the SSAGA provided diagnoses and symptom counts for alcohol abuse and dependence; the number of alcohol dependence symptoms was used instead of the full diagnosis, as the latter was rare at this age. Finally, parental education was assessed for mothers and fathers, with categories ranging from compulsory schooling only to tertiary education. The highest education of either parent was used as a covariate. A more detailed description of the potential confounders is shown in the Supplement 1.
