Background: Smoking rates in adolescents are rising in some countries. Helping young people to avoid starting smoking is a widely endorsed goal of public health, but there is uncertainty about how to do this. Schools provide a route for communicating with a large proportion of young people, and school-based programmes for smoking prevention have been widely developed and evaluated.
Objectives: To review all randomized controlled trials of behavioural interventions in schools to prevent children (aged 5 to12) and adolescents (aged 13 to18) starting smoking.
Search strategy: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) and the Cochrane Tobacco Addiction Group's Specialized Register, MEDLINE, EMBASE, PsyclNFO, ERIC, CINAHL, Health Star, Dissertation Abstracts and studies identified in the bibliographies of articles. Individual MEDLINE searches were made for 133 authors who had undertaken randomized controlled trials in this area.
Selection criteria: Types of studies: those in which individual students, classes, schools, or school districts were randomized to the intervention or control groups and followed for at least six months.
Types of participants: Children (aged 5 to12) or adolescents (aged 13 to18) in school settings. Types of interventions: Classroom programmes or curricula, including those with associated family and community interventions, intended to deter use of tobacco. We included programmes or curricula that provided information, those that used social influences approaches, those that taught generic social competence, and those that included interventions beyond the school into the community. We included programmes with a drug or alcohol focus if outcomes for tobacco use were reported. Types of outcome measures: Prevalence of non-smoking at follow up among those not smoking at baseline. We did not require biochemical validation of self-reported tobacco use for study inclusion.
Data collection and analysis: We assessed whether identified citations were randomized controlled trials. We assessed the quality of design and execution, and abstracted outcome data. Because of the marked heterogeneity of design and outcomes, we computed pooled estimates only for those trials that could be analyzed together and for which statistical data were available. We predominantly synthesized the data using narrative systematic review. We grouped studies by intervention method (information; social competence; social influences; combined social influences/social competence; multi-modal programmes). Within each group, we placed them into three categories (low, medium and high risk of bias) according to validity using quality criteria for reported study design.
Main results: Of the 94 randomized controlled trials identified, we classified 23 as category one (most valid). There was one category one study of information-giving and two of teaching social comeptence. There were thirteen category one studies of social influences interventions. Of these, nine found some positive effect of intervention on smoking prevalence, and four failed to detect an effect on smoking prevalence. The largest and most rigorous study, the Hutchinson Smoking Prevention Project, found no long-term effect of an intensive eight-year programme on smoking behaviour. There were three category one RCTs of combined social influences and social competence interventions: one provided significant results and one only for instruction by health educators compared to self-instruction. There was a lack of high quality evidence about the effectiveness of combinations of social influences and social competence approaches. There was one category one study providing data on social influences compared with information giving. There were four category one studies of multi-modal approaches but they provided limited evidence about the effectiveness of multi-modal approaches including community initiatives.
Authors' conclusions: There is one rigorous test of the effects of information-giving about smoking. There are well-conducted randomized controlled trials to test the effects of social influences interventions: in half of the group of best quality studies those in the intervention group smoke less than those in the control, but many studies failed to detect an effect of the intervention. There are only three high quality RCTs which test the effectiveness of combinations of social influences and social competence interventions, and four which test multi-modal interventions; half showed significant positive results.