Cannabis Use Amplified a Brain Marker of Psychosis Risk in Early-Stage Patients
A PET imaging study found that cannabis use was associated with significantly lower MAO-B levels, a marker of astrocyte function, in the brains of people with early psychosis and high-risk states, with the strongest effects in the striatum.
Quick Facts
What This Study Found
Cannabis use had a significant effect on MAO-B availability (F=12.57, p=0.001, Cohen's f=0.57), with a significant group-by-cannabis interaction (p=0.03) showing lower MAO-B in cannabis-using clinical groups. Lower MAO-B was more pronounced in striatal than cortical regions. The clinical high-risk group showed significantly lower MAO-B than healthy volunteers (Cohen's d=0.99).
Key Numbers
n=38 total (14 FEP, 7 CHR, 17 HV); cannabis effect F=12.57, p=0.001, Cohen's f=0.57; group-by-cannabis interaction F=3.82, p=0.03; CHR vs HV Cohen's d=0.99; striatal effects stronger than cortical.
How They Did This
PET brain imaging study using [11C]SL25.1188 radiotracer to measure MAO-B (an astrocyte marker) in 14 antipsychotic-free first-episode psychosis patients, 7 clinical high-risk individuals, and 17 healthy volunteers, controlling for tobacco and cannabis use.
Why This Research Matters
This is one of the first studies to show that cannabis use may specifically worsen astrocyte dysfunction in people at risk for or experiencing early psychosis. The finding connects cannabis use to a concrete brain-level change (lower MAO-B in astrocytes) that is linked to dopamine elevation in psychosis.
The Bigger Picture
Astrocyte dysfunction is an emerging focus in schizophrenia research, supported by post-mortem, genetic, and preclinical evidence. This study adds cannabis as a factor that may exacerbate astrocyte problems in vulnerable individuals, offering a potential biological mechanism for the cannabis-psychosis link.
What This Study Doesn't Tell Us
Small sample sizes, especially the CHR group (n=7). Cross-sectional design cannot determine temporal direction. Cannabis use was not the primary exposure of interest. Cannot determine whether cannabis directly causes lower MAO-B or whether individuals with lower MAO-B are more likely to use cannabis.
Questions This Raises
- ?Does cannabis directly reduce MAO-B in astrocytes, or is this an indirect effect?
- ?Would cannabis cessation normalize MAO-B levels?
- ?Could MAO-B imaging identify individuals at highest risk for cannabis-related psychosis?
Trust & Context
- Key Stat:
- Cannabis use amplified astrocyte dysfunction in early psychosis brains, especially in the striatum
- Evidence Grade:
- Moderate: PET imaging provides direct brain-level evidence with strong effect sizes, though small sample sizes (especially CHR n=7) limit generalizability.
- Study Age:
- Published in 2025.
- Original Title:
- Evidence of altered monoamine oxidase B, an astroglia marker, in early psychosis and high-risk state.
- Published In:
- Molecular psychiatry, 30(5), 2049-2058 (2025)
- Authors:
- Nisha Aji, Kankana(2), Lalang, Nittha(2), Ramos-Jiménez, Christian(3), Rahimian, Reza, Mechawar, Naguib, Turecki, Gustavo, Chartrand, Daniel, Boileau, Isabelle, Meyer, Jeffrey H, Rusjan, Pablo M, Mizrahi, Romina
- Database ID:
- RTHC-07260
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
What is MAO-B and why does it matter for psychosis?
MAO-B (monoamine oxidase B) is an enzyme found primarily in astrocytes, a type of brain cell. It helps break down dopamine. Lower MAO-B means less dopamine breakdown, which is consistent with the dopamine excess found in psychosis. Astrocyte dysfunction is increasingly recognized as part of schizophrenia biology.
Does this prove cannabis causes psychosis?
No, but it provides a biological mechanism by which cannabis could worsen psychosis risk. The study found that cannabis use was associated with lower MAO-B specifically in clinical groups (not healthy volunteers), suggesting cannabis may interact with pre-existing vulnerability rather than affecting all brains equally.
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Cite This Study
https://rethinkthc.com/research/RTHC-07260APA
Nisha Aji, Kankana; Lalang, Nittha; Ramos-Jiménez, Christian; Rahimian, Reza; Mechawar, Naguib; Turecki, Gustavo; Chartrand, Daniel; Boileau, Isabelle; Meyer, Jeffrey H; Rusjan, Pablo M; Mizrahi, Romina. (2025). Evidence of altered monoamine oxidase B, an astroglia marker, in early psychosis and high-risk state.. Molecular psychiatry, 30(5), 2049-2058. https://doi.org/10.1038/s41380-024-02816-x
MLA
Nisha Aji, Kankana, et al. "Evidence of altered monoamine oxidase B, an astroglia marker, in early psychosis and high-risk state.." Molecular psychiatry, 2025. https://doi.org/10.1038/s41380-024-02816-x
RethinkTHC
RethinkTHC Research Database. "Evidence of altered monoamine oxidase B, an astroglia marker..." RTHC-07260. Retrieved from https://rethinkthc.com/research/nisha-2025-evidence-of-altered-monoamine
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.