Time-Varying Treatment Effects: The Role of Anhedonia in Smoking Quit Attempts

Introduction. Recent studies suggest that anhedonia, the inability to experience pleasure from typically enjoyable activities, may play a key role in smoking cessation attempts (Cook et al., in press; Leventhal et al., 2013). This relatively understudied construct may be key to more successful quit attempts. In this study, we analyzed ecological momentary assessments (EMA) from a smoking cessation trial to (1) study the course of anhedonia and its association with craving and negative affect during the critical two-week period following quitting smoking, and (2) estimate the time-varying effect of smoking cessation therapies, both with and without bupropion, on these dynamic processes.

Methods. Data were from 1123 adults (58% female) from a randomized controlled trial of smoking cessation therapies. Participants were assigned to one of 6 conditions, coded placebo (N=131), bupropion (alone or with nicotine lozenge; N=402), and nicotine replacement therapy only (lozenge, patch, both; N=590). Participants were prompted to complete EMA assessments on mood and craving 4 times per day and anhedonia daily for two weeks after quitting, resulting in 25,141 assessments. We used time-varying effect models to examine mean anhedonia and its associations with other withdrawal symptoms as a function of time and treatment group.

Results. Preliminary results indicate that the placebo group had an elevated mean level of anhedonia immediately after quitting, which fell to levels similar to the treatment groups after Day 7. Nicotine replacement therapies were effective at reducing anhedonia early in the quit attempt. The time-varying association between craving and anhedonia was complex and varied across treatment groups. For the placebo and bupropion groups, these constructs were positively associated between Days 1-7 but thereafter not significant. For the nicotine replacement group, however, craving and anhedonia were not associated at any time. The positive association between negative affect and anhedonia was modest but stable over time throughout the study period for both active treatment groups, however for the placebo group this association was quite strong during Days 1-6 but non-significant thereafter.

Discussion. Understanding the time-varying associations of anhedonia with other dimensions of nicotine withdrawal may help researchers better understand processes contributing to smoking relapse, and may guide the development of intervention approaches that adapt in real time with the changing needs of individuals. Novel analytic approaches now exist to enable researchers to empirically investigate how treatment effects unfold as a nonparametric function of time – operating directly on an outcome such as anhedonia, as well as on associations between key constructs.