Affective and Neural Correlates of Nicotine and Cannabis Co-Use in Young Adulthood

Co-use of tobacco and cannabis is increasingly prevalent and is associated with greater risks compared to use of either substance alone. Co-use rates are elevated in young adulthood, but factors that maintain co-use in this age group are less well known. Individual differences in positive affect response to drug use and neural reward reactivity are important predictors of drug use maintenance and potential problematic use patterns, and prior research suggests these affective and neural correlates are related. Research is needed to characterize these two important factors in drug use maintenance in young adults who co-use nicotine and cannabis to further understand vulnerability for problematic use patterns in this population. A subset of young adults enrolled in an observational study utilizing Ecological Momentary Assessment (EMA) to assess the context and subjective experience of cannabis and nicotine co-use were recruited to participate in the current study, where they completed a task to measure neural reward reactivity during electroencephalogram (EEG). Current study aims included: 1) Examine subjective positive affect across cannabis-only, tobacco-only, and co-use times on EMA, 2) Examine relationships between EMA-assessed positive affect and reward reactivity, 3) Determine whether levels of cannabis and nicotine use moderate the relationship between neural reward reactivity and EMA-assessed positive affect. Results suggest that positive affect was elevated at cannabis use and co-use times, relative to non-use times, but not consistently at nicotine-only times. Greater positive affect following co-use was significantly predictive of greater neural reactivity to non-drug rewards. Rates of nicotine and cannabis use were not significant moderators. Overall, current findings suggest that in a young adult co-use population, greater positive reinforcement in the moments following co-use is significantly related to greater neural sensitivity to non-drug rewards when not using drugs. These findings potentially point to why certain individuals are vulnerable to maintaining co-use despite known associated risks.