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Citation

McMillan L & Ford A (2024) Understanding the mechanisms through which an e-cigarette intervention produced changes in smoking behaviour among people accessing homelessness services: findings from a mixed methods process evaluation. Society for the Study of Addiction (SSA), Newcastle, 13.11.2024-15.11.2024.

Abstract
Background/aims Around 80% of people experiencing homelessness smoke. Mechanisms leading to cessation in this group are not well understood. Our cluster randomised controlled trial found that e-cigarettes (ECs) were not effective for sustained 24-week abstinence although there were significant smoking reductions. An embedded process evaluation aimed to explore the mechanisms through which the intervention produced changes in smoking behaviour. Methods Mechanisms of change (MoC) (capability, opportunity, and motivation) were explored quantitatively via process measures in questionnaires and qualitatively via interviews with staff (n=16) and participants (n=32). Qualitative data was thematically analysed using deductive and inductive approaches. Quantitative measures were analysed descriptively. Data from the two approaches were combined for a detailed examination of MoC. Results Participants demonstrated high capability to use ECs. Opportunity was strengthened by social support and increases in vaping acceptability, but unstable living situations, stress, and smoking environments hindered opportunity. Motivation was enhanced by including CO readings, but negatively impacted by adverse effects. Confidence and self-efficacy to quit was driven by smoking reduction and enhanced future quitting beliefs. Conclusions An EC intervention can lead to positive behaviour change in smoking reduction by enhancing capability and motivation to use ECs among people experiencing homelessness.