Aim To examine self-efficacy and program exposure as possible mediators observed treatment effects for a web-based tobacco cessation intervention.
Design The ChewFree trial used a two-arm design to compare tobacco abstinence at both the 3- and 6-month follow-up for participants randomized to either an enhanced intervention condition or a basic information-only control condition.
Setting Internet in US and Canada.
Participants Our secondary analyses focused upon 402 participants who visited the web-based program at least once, whose baseline self-efficacy rating showed room for improvement, who reported that they were still using tobacco at the 6-week assessment, and for whom both 3- and 6-month follow-up data were available.
Intervention An enhanced web-based behavioral smokeless tobacco cessation intervention delivered program content using text, interactive activities, testimonial videos and an ask-an-expert forum and a peer forum. The basic control condition delivered tobacco cessation content using static text only.
Measurements Change in self-efficacy and program exposure from baseline to 6 weeks were tested as simple and multiple mediators on the effect of treatment condition on point-prevalence tobacco abstinence measured at 3- and 6-month follow-up.
Findings While both participant self-efficacy and program exposure satisfied the requirements for simple mediation, only self-efficacy emerged as a mediator when we used the more robust test of multiple mediation.
Conclusions Results confirm the importance of self-efficacy change as a probable underlying mechanism in a successful web-based behavioral intervention. While program exposure was found to be a simple mediator of tobacco abstinence, it failed to emerge as a mediator when tested with self-efficacy change in a multiple mediator test suggesting that self-efficacy and program exposure share a complex, possibly reciprocal relationship with the tobacco abstinence outcome. Our results underscore the utility of searching for mediators in research on web-based interventions.