Perceived Medication Assignment during a Placebo-Controlled Laboratory Study of Varenicline: Temporal Associations of Treatment Expectancies with Smoking-Related Outcomes

Expectancies regarding treatment assignment may influence outcomes in placebo-controlled trials above and beyond actual treatment assignment. For smoking pharmacotherapies, guessing enrollment in the active medication treatment is associated with higher abstinence rates. However, placebo-controlled trials of smoking pharmacotherapies rarely assess perceived treatment assignment and those that do only collect this information after reaching full dosage. To determine the temporal relationship between treatment expectancies and smoking-related variables, we assessed the impact of treatment guess during a placebo-controlled laboratory study of varenicline on measures of craving, smoking reward, and smoking reinforcement. We hypothesized that treatment guess at mid-titration would influence smoking-related measures at full dosage, above and beyond actual medication effects. We also explored factors related to guess stability and differences in blind fidelity between mid-drug titration and full dosage. Eighty-eight participants completed laboratory assessments at baseline, mid-titration, and full dosage that involved self-report and behavioral measures of tonic craving, cue-provoked craving, smoking reward, and smoking reinforcement. Participants guessed treatment assignment at mid-titration and full dosage. Generalized linear models confirmed that, beyond actual treatment assignment, treatment guess improved model fit for both self-report and behavioral smoking-related measures. Further, accuracy of treatment guess improved from titration to full dosage, and specific demographic factors (e.g., gender, race) were associated with type of treatment guess and guess stability across time. These results reinforce the importance of assessing perceived treatment assignment repeatedly during placebo-controlled trials and suggest that treatment expectancies during titration can affect outcomes once full dosage has been reached.