THC appears to disrupt reward-related brain regions in ways that correlate with psychotic symptoms, while CBD may push those same regions in the opposite direction.
Neuroscience researchers, clinicians treating psychosis, and anyone interested in the biological basis of cannabis-related psychosis risk.
THC and CBD modulated the same reward and salience brain regions in opposite directions
What the researchers found
THC modulated activity in the striatum, midbrain, insula, and anterior cingulate during reward processing, with some effects correlating with the severity of THC-induced psychotic symptoms. CBD appeared to modulate the same reward and salience regions in the opposite direction.
Why it matters
Both psychosis and THC use involve altered dopamine signaling in the striatum. Understanding whether cannabinoid effects on reward processing underlie psychotic symptoms could clarify why some cannabis users develop psychosis while others do not.
The numbers in context
People with psychosis show increased striatal presynaptic dopamine synthesis and release. Cannabis users generally show impaired presynaptic dopaminergic function, though acute THC challenges produced only modest effects on striatal dopamine.
How the study worked
Narrative review combining preclinical and human neuroimaging evidence. A systematic search identified acute cannabinoid drug-challenge studies using neuroimaging in healthy subjects and people with psychosis.
What this study cannot tell us
Narrative review rather than systematic meta-analysis. Acute THC challenge studies may not reflect chronic cannabis use. The relationship between reward processing changes and psychotomimetic effects remains correlational.
How to read the evidence
Narrative review synthesizing preclinical and human imaging data with some systematic search elements.
When this study was published
Published in 2022, reviewing literature up to that point.
The bigger picture
The overlap between cannabinoid effects on reward circuitry and the neurobiology of psychosis raises the question of whether endocannabinoid dysfunction and reward processing abnormalities are mechanistically linked in psychotic disorders.
Questions still open
- Does CBD's opposing effect on reward regions explain its potential antipsychotic properties? Could individual differences in reward circuitry predict psychosis risk from cannabis use?
Common questions
Does THC cause psychosis through the reward system?
Can CBD counteract THC's effects on the brain?
Read the original research
Cannabinoids, reward processing, and psychosis.
Psychopharmacology, 239(5), 1157-1177
Citation
Gunasekera, Brandon; Diederen, Kelly; Bhattacharyya, Sagnik. (2022). Cannabinoids, reward processing, and psychosis.. Psychopharmacology, 239(5), 1157-1177. https://doi.org/10.1007/s00213-021-05801-2
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