[School-based cannabis prevention: Results of a cluster-randomised trial].

Acluster-randomised trial was conducted in five German federal states to evaluate the results of a school-based cannabis prevention unit. A total of 55 schools were randomly assigned to the intervention group, i.e. participation in a two-hour cannabis prevention workshop conducted by drug prevention specialists in grades 8 and 9, or to a control group with a waiting list. The knowledge, attitudes, intentions and behaviour of the young people in relation to cannabis were measured at the start of the study and six months later. 2,669 pupils(50.8% girls, average age=14.12 years) made up the sample. Effects of the intervention on the students' knowledge (adjusted regression coefficient=0.26 [0.15-0.38], p<0.001) and on the expected negative consequences of cannabis use in adolescents (adjusted regression coefficient=0.15 [0.04-0.25], p=0.006) were found. Both increased significantly more in the intervention group compared to the control group. There were no effects on other attitude-related variables, intentions or behaviour. A very short school-based workshop for grade 8 and 9 students improved their knowledge of and critical attitudes towards cannabis use, but had no effect on their future intentions and cannabis use.