Impact of a 2-year multimodal intervention for disruptive 6-year-olds on substance use in adolescence: randomised controlled trial.

Background: Adolescent substance use is associated with both earlier childhood behavioural problems and serious lifetime addiction problems later in life.
Aims: To examine whether, and through which mechanisms, targeting risk factors in early childhood prevents substance use across adolescence.
Method: Disruptive kindergarten boys (n = 172) living in Montreal were randomly allocated to a preventive intervention and a control condition. The intervention was delivered over 2 years (7-9 years of age) with two main components: (a) social and problem-solving skills training for the boys; and (b) training for parents on effective child-rearing skills.
Results: Adolescent substance use, up to 8 years post-intervention, was reduced in those who received the intervention (d = 0.48-0.70). Of most interest, the intervention effects were explained partly by reductions in impulsivity, antisocial behaviour and affiliation with less deviant peers during pre-adolescence (11-13 years).
Conclusions: Adolescent substance use may be indirectly prevented by selectively targeting childhood risk factors that disrupt the developmental cascade of adolescent risk factors for substance use.