Psychosis patients who used cannabis had better social functioning before getting sick | Research

The takeaway

In a multisite study of 948 first-episode psychosis patients and 1,313 controls across 6 countries, cannabis-using patients had better premorbid social functioning than non-using patients, suggesting social ability may facilitate cannabis exposure.

Psychosis researchers, clinicians assessing cannabis-related risk, and those interested in premorbid predictors of mental illness.

Cannabis-using psychosis patients had better premorbid social functioning

What the researchers found

Psychosis patients who used cannabis occasionally or daily had better premorbid social adjustment than patients who never used. This difference was specific to patients and not seen in controls. IQ was 3 points higher in occasional users vs. never-users in both groups.

Why it matters

This challenges the idea that cannabis use alone explains cognitive differences between psychosis patients. Instead, it suggests that patients who were more socially functional before illness were more likely to encounter and use cannabis.

The numbers in context

948 FEP patients, 1,313 controls, 6 countries. IQ was 3 points higher in occasional users vs. never-users (both groups). Daily users had worse academic adjustment than occasional or never-users (both groups).

How the study worked

Multisite case-control study across 6 countries comparing IQ and premorbid adjustment (academic and social) by cannabis use frequency in 948 first-episode psychosis patients and 1,313 population controls.

What this study cannot tell us

Cross-sectional assessment of premorbid functioning relies on retrospective reports. The study cannot determine the direction of causation between social functioning, cannabis use, and psychosis onset.

How to read the evidence

Strong: large multisite case-control study across 6 countries with over 2,200 participants.

When this study was published

Published in 2020 in Schizophrenia Bulletin.

The bigger picture

The finding reframes the cannabis-psychosis relationship: rather than cannabis use being purely a risk factor, better premorbid social functioning may have increased the likelihood of cannabis exposure, which then interacted with existing vulnerability.

Questions still open

Does better social functioning increase cannabis exposure, which then triggers psychosis in vulnerable individuals? Should prevention strategies focus on socially active youth with psychosis risk factors?

Common questions

Does cannabis make people with psychosis smarter?

No. The study found that psychosis patients who used cannabis were already more socially functional before becoming ill. Their better social skills likely made them more likely to be in situations where cannabis was available.

What about the IQ difference?

Occasional cannabis users (both patients and controls) had IQ scores about 3 points higher than never-users. This small difference was not specific to psychosis and may reflect broader socioeconomic or social factors.

Read the original research

Premorbid Adjustment and IQ in Patients With First-Episode Psychosis: A Multisite Case-Control Study of Their Relationship With Cannabis Use.

Schizophrenia bulletin, 46(3), 517-529

View on PubMed ↗Publisher’s paper ↗

Citation

Ferraro, Laura; La Cascia, Caterina; Quattrone, Diego; Sideli, Lucia; Matranga, Domenica; Capuccio, Veronica; Tripoli, Giada; Gayer-Anderson, Charlotte; Morgan, Craig; Sami, Musa B; Sham, Pak; de Haan, Lieuwe; Velthorst, Eva; Jongsma, Hannah E; Kirkbride, James B; Rutten, Bart P F; Richards, Alexander L; Roldan, Laura; Arango, Celso; Bernardo, Miquel; Bobes, Julio; Sanjuan, Julio; Santos, Jose Luis; Arrojo, Manuel; Tarricone, Ilaria; Tortelli, Andrea; Szöke, Andrei; Del-Ben, Cristina Marta; Selten, Jean-Paul; Lynskey, Michael; Jones, Peter B; Van Os, Jim; La Barbera, Daniele; Murray, Robin M; Di Forti, Marta. (2020). Premorbid Adjustment and IQ in Patients With First-Episode Psychosis: A Multisite Case-Control Study of Their Relationship With Cannabis Use.. Schizophrenia bulletin, 46(3), 517-529. https://doi.org/10.1093/schbul/sbz077