Objectives: Assess effectiveness of mentoring to prevent adolescent alcohol/drug use.

Conclusions: All four RCTs were in the US, and included “deprived” and mostly minority adolescents. Participants were young (in two studies age 12, and in two others 9-16). All students at baseline were non-users of alcohol and drugs. Two RCTs found mentoring reduced the rate of initiation of alcohol, and one of drug usage. The ability of the interventions to be effective was limited by the low rates of commencing alcohol and drug use during the intervention period in two studies (the use of marijuana in one study increased to 1% in the experimental and to 1.6% in the control group, and in another study drug usage rose to 6% in the experimental and 11% in the control group). However, in a third study there was scope for the intervention to have an effect as alcohol use rose to 19% in the experimental and 27% in the control group. The studies assessed structured programmes and not informal mentors.