Across five European countries, cannabis use accounted for very little of the elevated psychosis risk among non-Western ethnic minorities, with two notable exceptions among specific Caribbean and Surinamese groups.
Psychiatry researchers, public health officials, and anyone interested in psychosis risk factors
Adjusting for cannabis barely changed the 1.80 odds ratio for psychosis in minorities
What the researchers found
The odds ratio for psychotic disorder among non-Western minorities was 1.80, and adjusting for cannabis use frequency barely changed it (1.81). However, for Black Caribbean individuals in London, adjusting for high-potency cannabis use reduced the OR from 2.45 to 1.61, and for Surinamese/Dutch Antillean individuals in Amsterdam, adjusting for daily use reduced the OR from 2.57 to 1.67.
Why it matters
The elevated psychosis risk among ethnic minorities in Europe is well-documented but poorly understood. This study tests whether cannabis use, itself a risk factor for psychosis, explains the gap. For most groups, it does not, pointing to other factors like social adversity, discrimination, or urbanicity.
The numbers in context
Overall non-Western minority OR: 1.80 (95% CI: 1.39-2.33), minimally changed after cannabis adjustment: 1.81. Black Caribbean in London: OR dropped from 2.45 to 1.61 after high-potency cannabis adjustment. Surinamese/Dutch Antillean in Amsterdam: OR dropped from 2.57 to 1.67 after daily use adjustment. 825 patients and 1,026 controls across 5 countries.
How the study worked
Case-control study using EU-GEI data from Spain, Italy, France, UK, and Netherlands. 825 first-episode psychosis patients and 1,026 controls were compared. Odds ratios for psychosis were calculated for migrant groups with and without adjustment for cannabis use measures.
What this study cannot tell us
Case-control design has inherent limitations in establishing causation. Cannabis use was self-reported and may be underreported. The two subgroups where cannabis appeared to matter (Black Caribbean, Surinamese) had relatively small sample sizes, making those estimates less stable.
How to read the evidence
Large multi-country case-control study with appropriate adjustment for confounders, from a well-established research consortium.
When this study was published
2024 study
The bigger picture
This finding challenges a simple narrative that cannabis drives the ethnic disparity in psychosis rates. While cannabis use may contribute in specific subgroups, the broader picture suggests social and structural factors play a larger role for most minority populations in Europe.
Questions still open
- Why does cannabis appear to play a role for Black Caribbean and Surinamese groups but not others? Is it higher rates of high-potency use, different genetic vulnerability, or interaction with other social risk factors? What factors beyond cannabis explain the elevated risk?
Common questions
Does cannabis explain why ethnic minorities have higher psychosis rates?
Did high-potency cannabis matter more?
Read the original research
The contribution of cannabis use to the increased psychosis risk among minority ethnic groups in Europe.
Psychological medicine, 54(11), 2937-2946
Citation
Selten, J P; Di Forti, M; Quattrone, D; Jones, P B; Jongsma, H E; Gayer-Anderson, C; Szöke, A; Llorca, P M; Arango, C; Bernardo, M; Sanjuan, J; Santos, J L; Arrojo, M; Tarricone, I; Berardi, D; Lasalvia, A; Tosato, S; la Cascia, C; Velthorst, E; van der Ven, E M A; de Haan, L; Rutten, B P; van Os, J; Kirkbride, J B; Morgan, C M; Murray, R M; Termorshuizen, F. (2024). The contribution of cannabis use to the increased psychosis risk among minority ethnic groups in Europe.. Psychological medicine, 54(11), 2937-2946. https://doi.org/10.1017/S0033291724001004
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