A cluster-randomised controlled trial 3 in Australia included 2 105 adolescents (cohort of grade 7 students followed-up in grade 10; 2014; aged 15-16 years). The intervention invovlved strengthening individual (eg, problem solving) and environmental (eg, caring relationships at school) resilience protective factors of adolescents. No significant differences were found between intervention and control students for any primary (ever tobacco: OR 1.25, 95% CI 0.92 to 1.68, p=0.14; recent tobacco: OR 1.39, 95% CI 0.84 to 2.31, p=0.19; recent ever alcohol: OR 1.11, 95% CI 0.83 to 1.48, p=0.46; alcohol: OR 1.13, 95% CI 0.78 to 1.62, p=0.51; 'risk' alcohol: OR 0.98, 95% CI 0.70 to 1.36, p=0.89) or secondary outcomes (marijuana: OR 1.12, 95% CI 0.74 to 1.68, p=0.57; other illicit substance: OR 1.19, 95% CI 0.67 to 2.10, p=0.54; individual protective factors: MD=0, 95% CI -0.07 to 0.06, p=0.89; environmental protective factors: MD: -0.02, 95% CI -0.09 to 0.06, p=0.65).
A randomized clustered trial 4 with two intervention conditions (i.e. e-learning and integral) included a total of 3 784 students of 23 Dutch secondary schools. Main effect analyses showed no programme effects on incidences of alcohol consumption (life-time prevalence: e-learning condition: P = 0.549; integral condition: P = 0.351; 1-month prevalence: e-learning condition: P = 0.288; integral condition: B = 0.445), tobacco consumption (life-time prevalence: e-learning condition: P = 0.444; integral condition: P = 0.119; 1-month prevalence: e-learning condition: P = 0.746; integral condition: P = 0.093), or marijuana consumption (life-time prevalence: e-learning condition: P = 0.732; integral condition: P = 0.214).
A Cochrane review [Abstract] 1 included 17 studies (9 cluster randomised studies with 253 clusters and 8 individually randomised studies with 1 230 participants). Four types of intervention were evaluated: motivational interviewing or brief intervention, education or skills training, family interventions and multi-component community interventions. Many studies had methodological drawbacks, especially high levels of loss to follow-up. One study of motivational interviewing suggested that this intervention was beneficial on cannabis use. Three family interventions (Focus on Families, Iowa Strengthening Families Program and Preparing for the Drug-Free Years), each evaluated in only one study, suggested that they may be beneficial in preventing cannabis use. The studies of multi component community interventions did not find any strong effects on drug use outcomes, and the two studies of education and skills training did not find any differences between the intervention and control groups.
A systematic review 2 including 71 studies was abstracted in DARE. The majority of studies identified were evaluations of interventions introduced in schools and targeting alcohol, tobacco and marijuana simultaneously. The outcome measure was drug-using behaviour. Weighted mean effect size was 0.037 (p<0.002) for school-based interventions up to 1 year (11 studies), and 0.018 (p=0.016) for school-based studies lasting 2 years or longer (10 studies). Fail safe N was 944 for meta-analysis of studies with 1 year follow-up and 192 for meta-analysis of studies with >= 2 years follow-up.
Comment: The quality of evidence is downgraded by study limitations (particularly loss to follow-up) and heterogeneity of interventions.
Primary/Secondary Keywords