A meta-analysis of 23 programs found interactive school-based prevention programs produced a small but significant reduction in middle school cannabis use, with teacher-led programs being most effective.
Read this if you are a parent, educator, or policy maker interested in whether school drug prevention programs actually reduce teen cannabis use.
Teacher-delivered interactive programs were the most effective at reducing cannabis use
What the researchers found
This meta-analysis evaluated whether interactive (skill-building, participant-focused) drug prevention programs in middle schools reduced cannabis use among 12-14 year olds in North America.
Across 21 studies measuring cannabis use, the pooled effect size was small but statistically significant (d = -0.07, p < 0.01), favoring the prevention programs. This means interactive programs produced a modest reduction in cannabis use compared to control conditions.
However, the programs did not significantly affect intention to use cannabis (3 studies) or refusal skills (3 studies), suggesting the behavioral change in cannabis use occurred through mechanisms other than changing attitudes or building refusal abilities.
A key moderator finding was that teacher-delivered programs were significantly more effective (d = -0.08, p = 0.02) than programs delivered by other types of instructors. This suggests that the relationship between students and their regular teachers may enhance program effectiveness.
Why it matters
Schools invest substantial resources in drug prevention programs but the evidence for their effectiveness is often unclear. This meta-analysis provides quantitative evidence that interactive programs work, albeit modestly, and identifies teacher delivery as a key success factor.
The numbers in context
30 studies, 23 independent samples. Cannabis use effect: d = -0.07 (p < 0.01). Intention to use: not significant (k=3). Refusal skills: not significant (k=3). Teacher-delivered programs: d = -0.08 (p = 0.02).
How the study worked
Meta-analysis of 30 studies (23 independent samples) from January 1998 to March 2014. Included randomized and quasi-experimental evaluations of interactive school-based prevention programs for ages 12-14 in North American middle schools. Effect sizes (Cohen's d) calculated for cannabis use, intention to use, and refusal skills. Random effects models used.
What this study cannot tell us
The effect size, while significant, is small. The small number of studies measuring intention to use and refusal skills limits conclusions about mechanisms. Publication bias could inflate the estimated effect. The review covers programs through 2014 and may not reflect newer approaches.
How to read the evidence
Meta-analysis of randomized and quasi-experimental studies with clear methodology and moderator analyses. Strong evidence for a small effect.
When this study was published
Published in 2017, covering studies from 1998 to 2014.
The bigger picture
The small effect size is typical of universal prevention programs and should be interpreted in context. Even small reductions in cannabis use across entire school populations translate to meaningful numbers of adolescents who do not initiate use. The teacher-delivery finding has practical implications for how schools implement prevention curricula.
Questions still open
- What specific components of interactive programs drive the effect? Would longer or more intensive programs produce larger effects? Why do teacher-delivered programs work better, and can this insight improve non-teacher-delivered programs?
Common questions
Do school drug prevention programs work for cannabis?
What type of prevention program works best?
Read the original research
A Meta-analysis of the Effectiveness of Interactive Middle School Cannabis Prevention Programs.
Prevention science : the official journal of the Society for Prevention Research, 18(1), 50-60
Citation
Lize, Steven E; Iachini, Aidyn L; Tang, Weizhou; Tucker, Joshua; Seay, Kristen D; Clone, Stephanie; DeHart, Dana; Browne, Teri. (2017). A Meta-analysis of the Effectiveness of Interactive Middle School Cannabis Prevention Programs.. Prevention science : the official journal of the Society for Prevention Research, 18(1), 50-60. https://doi.org/10.1007/s11121-016-0723-7
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