The relationship between drinking and smoking in a clinical trial for smoking cessation and drinking reduction.

Heavy drinking smokers experience poorer smoking cessation outcomes. Less is known about the relationship between drinking and smoking among those who are trying to reduce or abstain from both substances. The present study used data from 115 heavy drinking smokers who completed a 12-week clinical trial comparing varenicline alone (1 mg/bid) versus varenicline (1 mg/bid) plus naltrexone (50 mg/day) for smoking cessation and drinking reduction. We tested whether drinking outcomes mediated the relationship between medication and cigarettes per smoking day (CPSD) during the active medication phase (Week 4, 8, and 12) and follow-up phase (Week 16 and 26). CPSD and drinking variables predicted respective use at subsequent time points ( p 's < .0001). Results revealed a nonsignificant mediation effect of our primary mediator drinks per drinking day (DPDD) at Week 12: 95% CI = [-1.03, .58] and Week 26: 95% CI = [-.09, .51], and our secondary mediators of percent heavy drinking days (PHDDs) and percent days abstinent (PDA) at Week 12: 95% CI = [-.14, .35] and Week 26: 95% CI = [-.15, .41]. Cross-lagged effects (e.g., Week 4 drinking predicting Week 8 smoking) were nonsignificant between DPDD and CPSD ( p 's ≥ .07), and PHDD and PDA and CPSD that met our a priori cutoff ( p 's ≥ .02). There was a significant relationship between drinking and smoking concurrently indicated by fixed error covariances (CPSD and DPDD: p < .01; CPSD and PDA p = .01). Our findings highlight an association between drinking and smoking behaviors, respectively, across the span of 6 months. (PsycInfo Database Record (c) 2021 APA, all rights reserved).