Cohabitation with a smoker and efficacy of cessation programmes: the mediating role of the theory of planned behaviour

Objective The present research sought to examine whether cohabitation with a smoker undermines smoking cessation among people engaged in a cessation programme and whether the components of the Theory of Planned Behaviour (TPB) act as mediating mechanisms. Design A prospective longitudinal study with online questionnaires was conducted among smokers living in Switzerland who enrolled in a 6-months smoking cessation programme. Main outcome measures Cohabitation with a smoker and the TPB constructs were assessed 10 days after the start of the programme (T1; N = 820). Smoking abstinence was measured at T1, and at 3-months (T2; N = 624) and 6-months follow-ups (T3; N = 354). Results Results showed that living with a smoker decreased the odds that smokers remained abstinent throughout the cessation programme. Furthermore, we found that cohabitation was negatively associated with subjective norm. Afterwards, subjective norm predicted intention to maintain smoking cessation, which, in turn, predicted smoking abstinence. Such mediation effects persisted at each time point. Conclusion The present research provided evidence that living with other smokers at home can lead to greater risks of relapsing among people engaged in a cessation programme. We discussed the role of smoking-related norms in the efficacy of cessation interventions. Supplemental data for this article is available online at https://doi.org/10.1080/08870446.2022.2041638 .