“In a previous study conducted as part of my master’s research, we identified a correlation between plasma cytokines and the first psychotic episode. Following up on this discovery and the consortium’s recent publication showing a higher incidence of psychosis among subjects who used cannabis on a daily basis, our next step was to see if the biological factor [inflammatory profile] affected the link between cannabis use and psychosis,” said Fabiana Corsi-Zuelli, first author of the article.
‘Immune dysregulation could modify the relationship between cannabis use and psychosis. Daily use of cannabis and the age of onset lesser than 17 interacted significantly with ICS.’
The study was part of a project conducted by the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (EU-GEI), a consortium of research centers in 13 countries, including Brazil. A total of 409 participants aged between 16 and 64 (153 were first-episode psychosis patients and 256 were community-based controls) participated. Variables like cannabis use frequency and onset age for psychosis were evaluated using the Cannabis Experience Questionnaire.
Along with this, plasma cytokines and transforming growth factor-β (TGF-β) were also measured.
The researchers computed an inflammatory composite score (ICS) that represents the systemic inflammatory state. The confounding factors considered were sex, age, ethnicity, educational level, body mass index, tobacco smoking, lifetime use of other drugs, and antipsychotic treatment.
The study found that the usage of cannabis on a daily basis and the age of onset lesser than 17 interacted significantly with ICS. Beyond the individual effects, these could potentially increase the odds of psychosis.
“Our findings show that frequent current use of cannabis or use of the drug in adolescence is a risk factor for psychosis. We didn’t detect the same correlation with occasional or recreational use. In the multicenter study, which included European cities with varying levels and types of cannabis availability, we also found that the risk of psychosis is greater in users of stronger cannabis strains with a THC content of 10% or higher,” added the principal investigator of the project is Cristina Marta Del-Ben.
The findings of the study were published in the journal Psychological Medicine.