[The evaluation of effectiveness of scholastic programs in the prevention of consumption of tobacco, alcohol and cannabis: what do meta-analyses tell us?].

Consumption of tobacco, alcohol and illegal drugs is a major public health problem in developed countries. The aim of the study is to describe the impact and associated characteristics of preventive programs addressed at those problems in the school setting. Meta-analysis focusing on evaluations of programs focusing on smoking, alcohol and/or cannabis at the school setting are reviewed. The search was done at Cochrane Library and Medline databases of articles published between 1993 and 1999, and including as keywords programs, education, drugs prevention, prevention, smoking, alcohol, school, adolescence, teenagers, young people, evaluation, health education, effectiveness, review, meta-analysis. We found 5 meta-analysis of programs summarizing the effect of preventive programs, most of them dealing with legal and illegal drugs. However, most of the interventions reporting changes in behavior measured only smoking. More effective interventions addressed social influences, used active methodology and were implemented by teachers or peers. The importance of booster sessions, the quality of implementation and thorough evaluation is stressed. Overall, meta-analysis of evaluated programs shows a small effect, although the population impact may be relevant. Some limitations point to new areas of interest for future research.