Brain reward function in young people with cannabis use disorder: A functional magnetic resonance imaging study

Background and Aims: Cannabis use disorder (CUD) affects ~50 million people globally. Neuroscientific theories suggest that a blunted neural response to non-drug rewards is a hallmark of substance use disorders; however, this remains untested in CUD. The current study tested whether brain reward system responses to the anticipation and feedback of monetary rewards differed in people with CUD and controls. Design: Observational study using functional magnetic resonance imaging (fMRI). Setting: Participants were recruited from universities and the community in Wollongong, Australia. Participants: Sixty-four individuals with CUD (20 female) and 28 controls (9 female), aged 18–32 years. Measurements: Participants completed a monetary incentive delay task during fMRI. We compared blood-oxygen-level-dependent responses during reward anticipation and reward feedback between the CUD and control groups using hypothesis-driven region of interest analyses in brain areas implicated in reward pathways (i.e., orbitofrontal cortex, cingulum, insula, putamen, dorsal caudate, ventral striatum) and data-driven whole-brain analyses, controlling for age, sex, alcohol use, and depressive symptoms. Correlations tested associations between beta values from regions showing statistically significant group differences and severity of cannabis use measured with the Cannabis Use Disorder Identification Test (CUDIT), as well as other cannabis use and mental health measures. Findings: In whole-brain analyses, the CUD group showed statistically significantly greater left medial/superior frontal activity during reward anticipation compared with the control group (p < 0.001). Activity in this region was not associated with CUDIT scores or any other cannabis use or mental health variables. All region of interest analyses were statistically non-significant (all p > 0.05). Conclusions: People with cannabis use disorder do not appear to show evidence of a hypoactive reward system on the Monetary Incentive Delay task compared with controls. There may be differences in non-reward regions, but these appear unrelated to cannabis use severity.