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.