3. Brain reward function in young people with a dsm-5 diagnosis of Cannabis Use Disorder: a fMRI study

Introduction/ issues: Cannabis use disorder (CUD) is highly prevalent and can be associated with significant adverse psychosocial outcomes that have been ascribed to aberrant reward brain pathways according to prominent neuroscientific theories of addiction. The neural mechanisms underlying CUD are unclear as no study has assessed reward brain function in a sample of cannabis users with a DSM-5 diagnosis of CUD.

Method/ approach : This pre-registered cross-sectional study (DOI:10.17605/OSF.IO/29EB4) used fMRI to map brain function during a reward processing task (MIDT), in 70 people with a CUD and 28 controls.

Key findings: The CUD compared to the control group showed greater brain function while anticipating rewarding vs neutral outcomes, in medial prefrontal and parietal regions (p<.05, k=10, cluster-wise corrected); and this was predicted by greater cannabis dosage and reaction times. CUD vs controls had greater brain activity when receiving rewards vs neutral outcomes, in deep brain nuclei and superior orbitofrontal regions (p<.01, k=10).

Discussions: Dysfunctional brain reward pathways implicated in disinhibition and motivation in CUD is consistent with neuroscientific theories of addiction largely based on substances other than cannabis. CUD might show overlapping neural abnormalities as those shown in other substance use disorders.