Psychological mediators of bupropion sustained-release treatment for smoking cessation

Abstract

Aim: The study aimed to test simultaneously our understanding of the effects of bupropion sustained-release (SR) treatment on putative mediators and our understanding of determinants of post-quit abstinence, including withdrawal distress, cigarette craving, positive affect and subjective reactions to cigarettes smoked during a lapse. The specificity of bupropion SR effects was also tested in exploratory analyses.

Design: Data from a randomized, placebo-controlled clinical trial of bupropion SR were submitted to mediation analyses.

Setting: Center for Tobacco Research and Intervention, Madison, WI, USA.

Participants: A total of 403 adult, daily smokers without contraindications to bupropion SR use.

Intervention: Participants were assigned randomly to receive a 9-week course of bupropion SR or placebo pill and to receive eight brief individual counseling sessions or no counseling.

Measurements: Ecological momentary assessment ratings of smoking behavior and putative mediators were collected pre- and post-quit.

Findings: Results of structural equation and hierarchical linear models did not support the hypothesis that bupropion SR treatment improves short-term abstinence by reducing withdrawal distress or affecting the subjective effects of a lapse cigarette, but provided partial support for mediation by cigarette craving reduction and enhanced positive affect. Bupropion SR effects on point-prevalence abstinence at 1 month post-quit were also mediated partially by enhanced motivation to quit and self-efficacy.

Conclusions: Results provided some support for models of bupropion SR treatment and relapse and suggested that motivational processes may partially account for bupropion SR efficacy.

Figure 1

Structural model applied to evening report data. Treatment condition (0=placebo, 1=bupropion SR) was included as a predictor of latent “Run-up Average,” “Post-quit Intercept,” (quit day level) and “Post-quit Slope” (change in level over 1 week) variables. Direct (c′) and indirect (a and b) paths linked treatment to the one-month point-prevalence outcome (1=abstinent in past 7 days, 0=any smoking in past 7 days). One baseline covariate (gender) is included for illustration purposes.

Figure 2

Estimated growth in candidate mediators of bupropion SR effects derived from HLM multilevel models of withdrawal distress, cigarette craving, and positive affect. Intercept and linear slope variables were estimated separately in each assessment epoch. The baseline intercept was set to 11:59 PM on Day -8 and the slope was estimated between Days -14 and -8. The treatment run-up intercept was set to 11:59 PM on Day -1 and the run-up slope was estimated between days -7 and 0. The post-quit intercept was set to 12:00 AM on the quit day (Day 0) and the post-quit slope was estimated between days 0 and 6.