Largest fMRI study found no reward processing differences between cannabis users and non-users

Cannabis users and controls had similar neural responses during reward anticipation and in reward-related brain regions during feedback. No User-Group or User-Group by Age-Group effects were found. Bayesian analysis supported these null findings. Adolescents showed no increased vulnerability compared to adults.

Part of the CannTeen study. 125 adult (26-29 years) and adolescent (16-17 years) cannabis users (1-7 days/week) and matched controls underwent fMRI during the Monetary Incentive Delay task. Region of interest analyses of ventral striatum and ventromedial prefrontal cortex, plus whole-brain analyses.

The widespread belief that cannabis "hijacks" the brain's reward system is not supported by this large, well-designed study. The null findings, backed by Bayesian analysis, suggest reward processing may be largely intact in regular cannabis users.

This challenges the "amotivation syndrome" narrative often applied to cannabis users. If the core reward system is functioning normally, the assumption that cannabis fundamentally alters motivation at a neural level may need reassessment.

Cross-sectional design cannot rule out pre-existing differences. The Monetary Incentive Delay task measures monetary reward, which may not capture all dimensions of motivation. Cannabis users were regular but not necessarily heavy users.