In the largest brain imaging study of reward processing and cannabis use to date (125 participants), cannabis users showed no differences from controls in reward anticipation or core reward regions during feedback.
Neuroscientists studying addiction, clinicians counseling cannabis users about brain effects, and policymakers evaluating cannabis risk narratives.
No reward processing differences in adolescent or adult cannabis users
What the researchers found
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.
Why it matters
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.
The numbers in context
125 participants total (adults 26-29 and adolescents 16-17). Cannabis users consumed 1-7 days per week. No differences in bilateral ventral striatum during anticipation. No differences in right ventral striatum or left vmPFC during feedback. Exploratory whole-brain analysis found greater fronto-parietal activity in users during feedback.
How the study worked
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.
What this study cannot tell us
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.
How to read the evidence
Moderate: largest study of its kind with Bayesian support for null findings, but cross-sectional design.
When this study was published
Published in 2022.
The bigger picture
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.
Questions still open
- Would heavier cannabis users show reward processing differences? Does the greater fronto-parietal activity during feedback have functional significance? Would longitudinal data reveal changes that cross-sectional data miss?
Common questions
Does this mean cannabis has no effect on the brain's reward system?
Were adolescents more vulnerable?
What is the CannTeen study?
Read the original research
Neural responses to reward anticipation and feedback in adult and adolescent cannabis users and controls.
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 47(11), 1976-1983
Citation
Skumlien, Martine; Mokrysz, Claire; Freeman, Tom P; Wall, Matthew B; Bloomfield, Michael; Lees, Rachel; Borissova, Anna; Petrilli, Kat; Carson, James; Coughlan, Tiernan; Ofori, Shelan; Langley, Christelle; Sahakian, Barbara J; Curran, H Valerie; Lawn, Will. (2022). Neural responses to reward anticipation and feedback in adult and adolescent cannabis users and controls.. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 47(11), 1976-1983. https://doi.org/10.1038/s41386-022-01316-2
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