Combining multiple brain imaging methods in 24 heavy cannabis users revealed co-altered brain structure and function linked to serotonergic, dopaminergic, and opioid receptor systems.
Neuroscientists, addiction researchers, and anyone interested in how cannabis affects brain chemistry beyond the endocannabinoid system.
Changes linked to serotonin, dopamine, and mu-opioid systems
What the researchers found
Two transmodal components significantly differed between heavy cannabis users and controls. Grey matter volume changes occurred primarily in cerebello-temporo-thalamic regions, while intrinsic neural activity changes appeared in fronto-parietal regions. These changes were associated with the serotonergic, dopaminergic, and mu-opioid receptor systems.
Why it matters
By combining structural, functional, and neurochemical data in people who use cannabis heavily but have no diagnosed disorder, this study reveals brain changes that occur even without clinical impairment.
The numbers in context
24 heavy cannabis users vs. 16 controls. Two significant transmodal components identified (GMV: p=0.01, ALFF: p=0.03). Associations found with serotonergic system (structure), and serotonergic, dopaminergic, and mu-opioid systems (function).
How the study worked
Multimodal MRI study of 24 heavy cannabis users without cannabis use disorder or other mental disorders vs. 16 controls. Used parallel independent component analysis combining structural MRI and resting-state fMRI, plus JuSpace toolbox for cross-modal correlations with nuclear imaging-derived neurotransmitter estimates.
What this study cannot tell us
Small sample (24 users, 16 controls). Cross-sectional design cannot determine if brain changes preceded or resulted from cannabis use. Participants without cannabis use disorder may not represent the broader user population.
How to read the evidence
Small but methodologically rigorous multimodal imaging study with novel analytical approach.
When this study was published
Published in 2022.
The bigger picture
The involvement of multiple neurotransmitter systems beyond the endocannabinoid system suggests cannabis has broader neurochemical effects than its primary receptor target would predict.
Questions still open
- Do these brain changes progress to clinical impairment with continued use? Are the serotonergic and opioid system changes reversible with abstinence?
Common questions
Does heavy cannabis use change brain structure?
Does cannabis affect brain systems beyond cannabinoid receptors?
Read the original research
Multimodal MRI data fusion reveals distinct structural, functional and neurochemical correlates of heavy cannabis use.
Addiction biology, 27(2), e13113
Citation
Hirjak, Dusan; Schmitgen, Mike M; Werler, Florian; Wittemann, Miriam; Kubera, Katharina M; Wolf, Nadine D; Sambataro, Fabio; Calhoun, Vince D; Reith, Wolfgang; Wolf, Robert Christian. (2022). Multimodal MRI data fusion reveals distinct structural, functional and neurochemical correlates of heavy cannabis use.. Addiction biology, 27(2), e13113. https://doi.org/10.1111/adb.13113
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