Cannabis clearly affects hippocampal function and structure, but the evidence that it increases striatal dopamine function, a key mechanism proposed for psychosis, is less robust than commonly assumed.
Psychosis researchers, neuroscientists studying cannabis and dopamine
Hippocampal effects: clear evidence. Striatal dopamine effects: less robust evidence.
What the researchers found
Using the MAM rodent model as a framework, the review found clear evidence that cannabis/cannabinoids affect hippocampal and medial temporal lobe function and structure. However, evidence that cannabis increases striatal dopamine function was less robust. Limited evidence existed for cannabis effects on cortical and striatal glutamate levels.
Why it matters
The dopamine hypothesis is central to understanding psychosis. If cannabis-related psychosis operates through hippocampal dysfunction rather than direct dopamine effects, it could change therapeutic approaches.
The numbers in context
No specific pooled statistics; the review synthesizes evidence across imaging and preclinical studies and finds the hippocampal evidence stronger than the striatal dopamine evidence.
How the study worked
Review using the methylazoxymethanol acetate (MAM) rodent model of psychosis as a framework to examine cannabis effects on hippocampal-striatal-dopamine pathways. Examines neuroimaging and preclinical evidence.
What this study cannot tell us
Relies on animal model as framework; limited human neuroimaging studies directly testing the proposed pathway; the MAM model may not perfectly recapitulate cannabis-related psychosis.
How to read the evidence
Focused review using a preclinical framework to organize human and animal evidence.
When this study was published
Published in 2020.
The bigger picture
The distinction between clear hippocampal effects and weaker dopamine evidence suggests the cannabis-psychosis pathway may be more nuanced than a simple "cannabis increases dopamine" narrative.
Questions still open
- Could hippocampal dysfunction be the primary mediator of cannabis-related psychosis risk? Would multimodal neuroimaging studies better capture the proposed pathway?
Common questions
Does cannabis increase dopamine and cause psychosis?
What is the MAM model?
Read the original research
Do the effects of cannabis on the hippocampus and striatum increase risk for psychosis?
Neuroscience and biobehavioral reviews, 112, 324-335
Citation
Daniju, Y; Bossong, M G; Brandt, K; Allen, P. (2020). Do the effects of cannabis on the hippocampus and striatum increase risk for psychosis?. Neuroscience and biobehavioral reviews, 112, 324-335. https://doi.org/10.1016/j.neubiorev.2020.02.010
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