Predicting Non-Adherence With Very Low Nicotine Content Cigarettes Among Adults With Serious Mental Illness Who Smoke

Reducing the nicotine content of cigarettes is a promising policy intervention to decrease cigarette dependence among people who smoke. Randomized trials support the potential efficacy of a reduced nicotine product standard for cigarettes. However, interpretation of such trials is challenged by incomplete adherence to the randomized treatment assignment, as some participants may continue to use commercial cigarettes not provided by the trial. The current study examined prevalence and predictors of non-adherence among trial participants with serious mental illness (SMI).

Adults with SMI who smoke daily and were not trying to quit (N = 58) were randomized to receive very low nicotine content (VLNC) or normal nicotine content cigarettes over 6 weeks. We investigated predictors of biologically assessed non-adherence in participants assigned to VLNC cigarettes (n = 30). Predictors included subjective responses to VLNC cigarettes, baseline nicotine dependence and dependence motives, and psychiatric symptom severity. We fit a series of linear models regressing non-adherence metrics onto covariates (gender; menthol preference) and focal predictors.

Nearly all participants (96%) were estimated to be less than completely adherent to VLNC cigarettes. Lower enjoyment ratings of respiratory tract sensations of VLNC cigarettes predicted a greater degree of non-adherence (b = -.40, SE = .14, 95% CI: -0.71, -0.10).

Less positive subjective response to smoking VLNC cigarettes was the only significant predictor of incomplete adherence among individuals with SMI, consistent with prior research in a general population sample. This suggests the potential for shared strategies to help different smoking populations adjust to a reduced nicotine product standard.

Results offer preliminary insight into potential barriers to adherence in SMI populations. Adherence might be enhanced by supplementing VLNC cigarettes with alternative sources of non-combusted nicotine, paired with educational campaigns to encourage quitting or switching to less harmful products. Future studies should replicate these analyses in a larger sample of individuals with SMI who smoke.