Study designs of evaluations included in the review
Studies of at least a quasi-experimental design comparing an intervention with a control group were eligible for inclusion. The unit of assignment in the included studies was schools, classrooms, Boys and Girls Clubs of America, communities, school districts and individuals. About half of the included studies used some type of matching or blocking to minimise baseline non equivalence.
Specific interventions included in the review
Studies using at least one school-based or community-based intervention were eligible for inclusion. All but one of the included studies used a school-based programme.
All studies included programmes addressing social influences to smoke and the development of skills to resist these pressures. Other programme elements included life skills training, factual information, public commitment and a community component. The programmes were delivered by a variety of personnel such as classroom teachers, research staff, health educators and peer leaders. The number of regular sessions varied widely (range: 5 to 384; median and mode 10), as did the length of the programme (range: 2 weeks to 8 years). Some programmes included booster sessions, which ranged from one session over 2 days to 15 sessions over 2 years.
Participants included in the review
Studies of adolescents who were aged less than 21 years at baseline were eligible for inclusion. Most of the included studies recruited 7th grade students, aged 12 to 13 years. Over the duration of the studies, the students ranged in age from 8 to 28 years. Generally, about half of the sample were female and most of the studies were conducted in predominantly white populations.
Outcomes assessed in the review
Studies that assessed the incidence or prevalence of tobacco use after at least 2 years for adolescents aged 12 to 15 years and 16 to 19 years were eligible for inclusion. The review also assessed the use of other drugs such as alcohol and marijuana. The included studies evaluated drug use using self-report questionnaires of lifetime or recent use and/or biochemical validation, or the bogus pipeline method. The duration of follow-up ranged from 24 months to 15 years.
How were decisions on the relevance of primary studies made?
The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.