Objective: Chronic cannabis use is maintained in part through dysregulated stress and reward response systems. Specifically, stress-related negative affect is thought to act as a salient motivator for chronic substance use. Models of addiction posit that the transition from positive to negative reinforcement motives for substance use is a key mechanism of disordered use. However, research in substance-using samples has not assessed stress-related neural processing of both positive and negative reinforcement. Method: Therefore, the present study utilized laboratory stress induction to examine how stress affects the reward positivity, an event-related potential sensitive to both positive (RewP) and negative (relief-RewP) reinforcement, in 87 cannabis users (58.10% female, M-age = 19.40) varying in cannabis use disorder (CUD) severity and, as part of larger study aims, history of traumatic brain injury (TBI). We predicted greater CUD severity would be associated with a blunted RewP and enhanced relief-RewP, particularly after stress induction, independent of TBI status. Results: Findings indicated that CUD severity was not associated with RewP/relief-RewP amplitude regardless of acute stress. Exploratory analyses revealed, however, that among those with history of TBI+, CUD severity was associated with greater stress-elicited blunting of the RewP and enhancement of the relief-RewP. Conclusion: Although initial findings contradict current allostatic models of addiction, exploratory findings suggest that history of TBI, and potentially other confounding variables related to increased risk of TBI experience, may influence the extent to which stressful experiences modulate the neurophysiology of both positive and negative reinforcement reward processing in CUD. Public Health Significance Statement The present study suggests that in people with history of TBI, greater disordered cannabis use is associated with a stress-elicited decrease in reward sensitivity to positive reinforcement, in addition to a simultaneous increase in sensitivity to negative reinforcement. Present results may inform future interventions targeting reward dysregulation in specific populations of disordered cannabis users.
