| Muilenburg JL et al. 2008 [47] | Southeastern USA 6 Public schools in 2006 | Cross-sectional | Part of National youth tobacco survey 990 boys 1071 girls | Ordered logit regression |
| Murnghan DA et al. 2007 [48] | Prince Edward Island, Canada, 10 English high schools from 1999-2001 | Cross-sectional | Not stated 3965 boys and girls | Multilevel logistic regression |
| Poulin CC et al. 2007 [49] | Atlantic province (Nova Scotia, New Brunswick, Prince Edward Island, Newfoundland & Labrador, Secondary schools in 2002 | Cross-sectional | Single stage cluster sample stratified by grade and either health regional or school district 6403 boys 6368 girls | Two level random effect model, Sensitivity analysis was performed using multinomial logistic regression |
| Ridout F et al. 2008 [50] | Hampshire and Central London, 12 Secondary schools. Data collection year not mentioned. | Cross-sectional | Convenience sampling 912 boys 853 girls | Chi-squared, logistic regression adjusted for clustering |
| Rodriguze D et al. 2007 [51] | USA, 5 Public schools. Data collected in 2003. | Longitudinal study over 4 years | Not stated 496 boys 467 girls | SEM, CFA |
| Schnohr CW et al. 2009 [52] | Denmark, Sweden, Norway, Finland, and UK secondary schools 2001-2002 | Cross-sectional | Data derived from a project (The health behaviour in school children) 20,399 boys and girls | Binary logistic regression analysis stratified by country |
| Sinha DN et al. 2007 [53] | India (North, Eastern, Western, North East), 179 schools in 2006 | Cross-sectional | Two stage cluster sampling Schools and classes selected randomly. All students selected within classes 12086 boys and girls | Logistic regression for clustered data |
| Sinha DN et al. 2008 [54] | India, 6 regions: North, South, East, West, Central & North East, 2003: 818 schools 2006:179 schools, | Cross-sectional | Two stage cluster sampling Schools selected proportional to number of students, and classes selected randomly. All students interviewed from selected classes 2003: 68,077 boys and girls 2006: 12,086 boys and girls | Logistic regression for correlated data |
| Thrasher JF et al. 2008 [55] | Mexico,18 Public & private schools in 2006 | Cross-sectional | Proportional sampling strategy to randomly select schools & classes 3874 boys and girls | Multilevel adjusted logistic regression model, SEM |
| Wen X et al. 2007 [56] | Huang pu and Guangzhou, China, 6 Secondary schools in 2004 | Cross-sectional | Cluster sampling of schools 2021 boys 1850 girls | Logistic regression |
| Wen X et al. 2008 [57] | Guangzhou, China, 3 Public schools, 1 Factory school 2 General paid private schools in 2004 | Cross-sectional | Multistage sampling with stratification by school type 3957 boys and girls and 2870 parents of these students | Chi-squared & Kruskal Wallis |