Four intervention studies (n=9,356) were included: three cluster RCTs (4, 8 and 12 intervention schools and 4, 8 and 14 control schools, respectively) and one quasi-experimental study with a matched control group (9 intervention schools and 3 control schools). The number of students per treatment group ranged from 366 to 2,221. Attrition rates ranged from 10 to 49%.
Two observational studies (7,164 students) measured school-level exposures using stratified random sampling . Seven observational studies (32,327 students) measured individual-level school-related exposures.
This abstract focuses on the intervention studies and studies assessing school-level associations.
Compared with the control group, one study reported a reduction in the rate of increase in a combined measure of alcohol, tobacco and cannabis use for boys exposed to the intervention; one study reported a significant reduction in the rate of increase in the use of drugs other than cannabis among boys, but not girls, exposed to the intervention; and one study reported a non significant reduction in cannabis use in the previous 6 months among young people exposed to the intervention. The study evaluating the implementation of new school rules reported no effect on the number of students using cannabis in intervention schools compared with control schools.
Observational studies reporting on school-level associations.
One study reported a significant association (after adjustment for confounders) between school-level rates of drug use at age 13 to 15 and reported disengagement and poor teacher-student relationships. The other study reported no association between policies about school uniform and drug use.
Observational studies reporting on individual-level associations.
Studies generally found associations between disengagement from school and poor teacher-student relationships and subsequent drug use.