2019 | Europe and Brazil | Multicenter case-control study
Di Forti M et al. The Lancet Psychiatry. 2019;6:427-436.
Methods: The EU-GEI study compared 901 people with first-episode psychosis with 1,237 population controls across 11 sites. Researchers examined use patterns and estimated product potency using available market information.
Findings: Daily use was associated with higher odds of psychotic disorder than never use. Daily use of products classified as high potency had an adjusted odds ratio of approximately 4.8 compared with never use.
Limitations: The design cannot by itself establish causation or an individual’s absolute risk. Recall, selection, and residual confounding can affect estimates. Odds ratios should not be described as the percentage of users who will develop psychosis.