Long-term effects of implementation intentions on prevention of smoking uptake among adolescents: a cluster randomized controlled trial.

OBJECTIVE: To test the efficacy of implementation intentions in reducing smoking uptake in a sample of adolescents. DESIGN: Classes of adolescents (aged 11-12 years) were randomly allocated to one of four conditions: implementation intention, self-efficacy, two control conditions. An implementation intention or a self-efficacy manipulation (both formed in relation to how to refuse offers of cigarettes) was completed by intervention condition participants at 0, 4, 8, 12, 16, 20, and 24 months. MAIN OUTCOME MEASURES: Long-term smoking behavior (self-report and objective) was assessed at 48 months post-baseline. RESULTS: There were no differences between the two control conditions and the self-efficacy condition. Controlling for baseline smoking, sex, attitudes to smoking, friends and family smoking, and the multilevel nature of the data, intention-to-treat analyses indicated the implementation intention manipulation significantly reduced self-reported smoking compared to the other three conditions combined. Analyses on objectively assessed smoking (carbon monoxide breath measure) in a random subsample of participants also indicated that the implementation intention manipulation compared to the other three conditions significantly reduced smoking. CONCLUSION: Implementation intentions can reduce smoking in adolescent samples. Implications for using implementation intentions to reduce smoking in adolescents are discussed.

Direct, mediated and moderated impacts of personality variables on smoking initiation in adolescents.

Role of 'Big Five' personality traits as predictors of smoking and moderators of the intention-smoking relationship was tested. Five hundred and fifty-three adolescents (aged 11-12) completed measures of self-reported past smoking, gender, intentions to smoke, perceived behavioural control, family smoking, friends smoking at times 1 and 2 (6 months apart). At time 3, 2 years later, the same adolescents completed measures of the Big Five and self-reported smoking (a subset of 300 also provided an objective smoking measure). At time 4, two years after time 3, a sub-sample of 122 adolescents provided a self-report measure of recent smoking. Simple correlations indicated significant direct effects of conscientiousness (self-reported smoking, times 3 and 4), extraversion (time 4 smoking) and neuroticism (all smoking measures) on smoking. Logistic regression showed intention, and the interaction between conscientiousness and intention to significantly predict both self-reported and objectively assessed smoking (both at time 3) after controlling for other variables. Multiple regression showed intentions, family smoking and the interaction between conscientiousness and intention to significantly predict self-reported smoking at time 4 after controlling for other variables. The findings indicate that the impact of personality variables on smoking is through mediated (through cognitions) and moderated (conscientiousness by intention interaction) pathways.