Differential Mechanisms of Change in Motivational Interviewing Versus Health Education for Smoking Cessation Induction

Objective: To determine if Motivational Interviewing (MI) versus health education (HE) elicited different types of client language and whether these differences were associated with outcomes in a randomized clinical trial (RCT) for cessation induction among people who smoke with low motivation to quit. Methods: A secondary data analysis was conducted using data from the MI and HE arms of a trial in which people who smoke (N = 202) with low desire to quit were randomly assigned to four sessions of MI, HE or brief advice. Mediation analyses examined two types of client language: change talk (CT) and a novel form of client speech called "learning talk" (LT). Outcomes were assessed at baseline, 3 and 6 months. Results: With HE as the reference group, MI resulted in greater CT (OR = 3.0, 95% CI: 1.7-5.5) which was associated with better outcomes (average d = .34, SD = .13) and HE resulted in greater LT (OR=.05, 95% CI:.02-.10) which was also associated with better outcomes (average d=.42, SD=.08). Indirect parallel mediation effects on quit attempts were significant for both MI-CT (OR = 1.4, 95% CI: 1.1-1.7) and HE-LT (OR=.4, 95% CI:.2-.7). Conclusions: MI and HE were both efficacious via different pathways to change, confirming the utility of MI in this RCT as well as highlighting the potential of HE based on the "5R's" for smoking cessation. These findings emphasize the value of exploring theorized mechanisms of action of interventions evaluated in RCTs.