Dr Martine Skumlien is a Research Associate in the Addictions Policy Research Unit at King’s College London. Her work focuses on evaluating and shaping drug and addictions policy, with a particular interest in harm reduction. She completed her PhD in Psychiatry at the University of Cambridge, investigating how cannabis use influences motivation and reward processing in the brain. She has also conducted mixed-methods research on drug checking and the detection of novel psychoactive substances at the University of Bath. Most recently, she was awarded a British Academy fellowship to explore interventions that encourage safer cannabis use and harm reduction behaviours.

Abstract

Brain reward function in young people with cannabis use disorder: An fMRI study

Cannabis use disorder (CUD) affects ~50 million people globally. Several prominent neuroscientific theories suggest that addiction is associated with blunted reward system responses to non-drug rewards. Previous empirical studies have found attenuated reward anticipation activity in some behavioural and substance use disorders, but this remains untested in CUD. The current study aimed to test whether CUD is associated with altered brain reward processing. Sixty-six individuals with CUD and 29 controls completed a Monetary Incentive Delay task during fMRI. Reward function was compared between groups in region-of-interest analyses in key brain reward regions (orbitofrontal cortex, cingulum, insula, putamen, dorsal caudate, ventral striatum) and a whole-brain analysis, controlling for age, gender, alcohol use, and depressive symptoms. Follow-up correlations were performed between clusters with a significant group difference and behavioural variables. The CUD group showed significantly greater left medial/superior frontal activity while anticipating monetary reward > anticipating neutral reward. This did not correlate with behavioural variables, including cannabis use metrics, motivation-related measures, alcohol use, tobacco use, or task reaction times. There were no differences during reward feedback or in region-of-interest analyses. The current study suggests that CUD may be associated with changes in the prefrontal cortex’ responses to monetary rewards. However, in contrast with previous studies and prominent theories of addiction, we did not find evidence of blunted reward anticipation activity in people with CUD. Future longitudinal studies in larger samples are needed to corroborate the current results.