Social norms as a predictor of smoking uptake among youth: a systematic review, meta?analysis and meta?regression of prospective cohort studies

BACKGROUND AND AIMS: Social norms towards smoking are a key concept in tobacco control policy and research. However, the influence strength of different types social on youth uptake is unclear. This study aimed to examine, quantify compare evidence longitudinal associations between (initiation escalation). METHODS: Systematic review searching four databases (MEDLINE, EMBASE, PsycInfo, CINAHL) from January 1998 October 2020. Evidence synthesis via narrative review, meta-analysis pooling unadjusted only, due heterogeneity escalation outcomes) meta-regression comparing effect sizes by norm type characteristics. Studies included observational prospective cohort studies using survey methodology with aged ?24 years. Measurements descriptive (perceived behaviour) injunctive approval/disapproval smoking) among network(s) subsequent initiation or escalation. RESULTS: Thirty articles were identified. In (but not escalation) was consistently predicted two norms: parental close friend smoking. Associations other (smoking siblings, family/household, partner, peers, adults) all approval parents, friends/peers, teachers, people important you, public) less consistent inconclusive. associations, 17 (n = 27?767). Smoking following parents [Odds Ratio (OR) = 1.88, 95% Confidence Interval (CI) = 1.56-2.28], friends (OR = 2.53, CI = 1.99-3.23), siblings (OR = 2.44, CI = 1.93-3.08), family/household (OR = 1.55, CI = 1.36-1.76) adults (OR = 1.34, CI = 1.02-1.75), but peers (OR = 1.14, CI = 0.92-1.42). also norms, perceived (OR = 1.74, CI = 1.27-2.38) public (OR = 4.57, CI = 3.21-6.49), friends/peers (OR = 2.36, CI = 0.86-6.53) individual (OR = 1.24, CI = 0.98-1.58). CONCLUSIONS: this systematic (narrative meta-analysis), parents' friends' behaviour appeared be predictors initiation, more so than distal networks norms.