A Mindfulness-Based Intervention to Reduce Altered Brain Reward Function in Cannabis Use Disorder: A Double-Blind, Active and Passive, Randomised Controlled fMRI Trial

Cannabis Use Disorder (CUD) affects ~50 million individuals worldwide and is associated with alterations in brain reward pathways. Mindfulness-based interventions (MBIs) show promise in reducing substance use and aberrant brain function in substance use disorders (SUD), but the effects on CUD or brain reward function have not been investigated. To examine whether a 2-week MBI vs. active control (i.e., closely matched relaxation) and passive control (i.e., no intervention) affected brain reward function in CUD using the Monetary Incentive Delay fMRI task, 49 individuals with moderate-to-severe CUD were randomised to: a 2-week MBI (n = 18), active control condition (n = 15), or passive control condition (n = 16), and assessed before and after the intervention. The effect of intervention-by-time was analysed using an exploratory whole-brain approach and a priori regions-of-interest approach (ROIs; ventral striatum, dorsal caudate, putamen, insula, cingulate, and orbitofrontal cortices). Whole-brain results revealed significant intervention-by-time effects. Post-MBI, there was: decreased cerebellum activity while anticipating monetary cues, increased parietal activity while receiving monetary wins, and decreased fusiform/superior frontal gyri (SFG) activity while receiving monetary wins. Post-relaxation, activity increased in several regions (i.e., hippocampus, insula, parietal cortex, fusiform, and SFG) during the receipt of monetary wins. Post-no intervention, activity increased in the cerebellum while anticipating monetary cues, and decreased in other areas (i.e., parietal cortex, hippocampus, and insula) while receiving monetary wins. There were no significant intervention-by-time effects using the ROI approach. Overall, MBI, matched relaxation, and no intervention may share changes in partially overlapping brain regions in distinct directions.