A Mediation Analysis of Motivational, Reduction, and Usual Care Interventions for Smokers Who Are Not Ready to Quit

We recently conducted a large randomized controlled trial (RCT) (N = 560) that failed to replicate our initial RCT's findings that brief motivational and reduction interventions increased quit attempts (QA) and point-prevalence abstinence (PPA) in smokers not ready to quit. The present study aimed to test why our interventions were ineffective.

A secondary analysis of a 3-arm RCT tested (1) whether telephone-based motivational or reduction interventions changed the following hypothesized mediators more than usual care: cigarettes per day (CPD), dependence, pros of smoking, cons of smoking, self-efficacy, or intention to quit; (2) whether changes in these hypothesized mediators predicted QAs and PPA at a 6-month follow-up, and (3) whether the interventions affected QAs and PPA via the hypothesized mediators.

In comparison to usual care, the motivational intervention did not significantly influence the hypothesized mediators. The reduction intervention resulted in a significantly greater decrease in CPD and pros of smoking and increase in self-efficacy and intention to quit than usual care. Decreases in CPD and dependence and increases in self-efficacy and intention to quit were associated with increased QAs. The reduction intervention's influence on QAs was mediated by decreases in CPD and increases in self-efficacy and intention to quit. Findings regarding PPA were similar.

Our failure to replicate may be due, in part, to the fact that, compared to usual care, (1) the motivational intervention had no effect on the hypothesized mediators, and (2) the reduction intervention had a statistically significant but clinically insignificant effect on the hypothesized mediators.

This study demonstrates that mediation analysis may be useful to understand why an intervention is not more effective than usual care. We identified reductions in CPD and dependence and increases in self-efficacy and intention to quit as predictors of quitting. Further research should focus on developing more effective interventions to target these constructs, and cause clinically significant changes among smokers who are not ready to quit.