Cannabis users who developed psychosis showed widespread grey matter loss compared to cannabis users without psychosis | Research

The takeaway

In a pilot MRI study, cannabis users with cannabis-induced psychosis had extensive grey matter reductions in multiple brain regions compared to non-psychotic cannabis users, suggesting psychosis involves additional brain damage beyond cannabis use alone.

Psychiatrists, neuroimaging researchers, people interested in cannabis and psychosis risk

8+ brain regions showed grey matter reductions in psychosis patients vs. non-psychotic users

What the researchers found

CIP patients showed extensive grey matter decreases in right superior frontal gyrus, precentral, superior temporal gyrus, bilateral insula, right precuneus, right medial occipital gyrus, right fusiform gyrus, and left hippocampus compared to non-psychotic chronic cannabis users. Grey matter volumes negatively correlated with BPRS-Activity scores in CIP patients.

Why it matters

Understanding what distinguishes cannabis users who develop psychosis from those who do not could identify biomarkers for psychosis risk before symptoms emerge.

The numbers in context

10 CIP patients vs. 12 non-psychotic cannabis users. Grey matter reductions found in 8+ brain regions. Negative correlation between BPRS-Activity and GM volumes in CIP group.

How the study worked

Pilot study comparing 3T MRI brain scans of 10 cannabis-induced psychosis patients with 12 non-psychotic chronic cannabis users. Sociodemographic, clinical, and psychosocial variables correlated with brain measures.

What this study cannot tell us

Very small pilot study; cross-sectional design cannot determine if brain changes preceded or followed psychosis onset; no healthy non-using control group; medication effects possible in CIP group.

How to read the evidence

Very small pilot study (n=22) without healthy controls; designed to generate hypotheses for larger studies.

When this study was published

Published in 2020.

The bigger picture

The selective brain reductions in psychosis patients suggest that cannabis-induced psychosis is not simply heavy cannabis use but involves additional neurobiological vulnerability or damage.

Questions still open

Do these brain reductions exist before psychosis onset and could serve as early warning signs? Would a larger study with healthy controls clarify which changes are cannabis-related vs. psychosis-specific?

Common questions

Do all heavy cannabis users develop these brain changes?

No. The brain reductions were found only in cannabis users who developed psychosis, not in those who used cannabis heavily without developing psychosis. This suggests additional vulnerability factors beyond cannabis use itself.

Could these brain changes be used to predict psychosis?

That is a possibility the authors suggest, but this pilot study was too small to establish predictive value. Larger prospective studies would be needed to determine if these patterns could identify at-risk individuals before psychosis develops.

Read the original research

Brain Morphology of Cannabis Users With or Without Psychosis: A Pilot MRI Study.

Journal of visualized experiments : JoVE

View on PubMed ↗Publisher’s paper ↗

Citation

Delvecchio, Giuseppe; Oldani, Lucio; Mandolini, Gian Mario; Pigoni, Alessandro; Ciappolino, Valentina; Schiena, Giandomenico; Lazzaretti, Matteo; Caletti, Elisabetta; Barbieri, Viviana; Cinnante, Claudia; Triulzi, Fabio; Brambilla, Paolo. (2020). Brain Morphology of Cannabis Users With or Without Psychosis: A Pilot MRI Study.. Journal of visualized experiments : JoVE. https://doi.org/10.3791/60881