Cannabis Directly Linked to Psychosis Relapse
Continuing to smoke cannabis after a first episode of psychosis is causally linked to an increased risk for psychosis relapse, new research shows.
The research, entitled “Association Between Continued Cannabis Use and Risk of Relapse in First-Episode Psychosis. A Quasi-Experimental Investigation Within an Observational Study”, was conducted at King’s College London, United Kingdom and shows that cannabis use is a “risk-modifying factor for relapse, suggesting that discontinuation of cannabis use after the onset of psychosis may help in reducing the risk of relapse.”
For their study, the researchers used a quasi-experimental design to explore the causal nature of the association between continued cannabis use and risk for psychosis relapse. A total of 220 patients with first-episode psychosis were included in the analysis (mean [SD] age, 28.62 [8.58] years; age range, 18-65 years; 90 women [40.9%] and 130 men [59.1%]).
Conclusions and Relevance
The study found that the relapse rate was highest for individuals who used cannabis continuously after first episode of psychosis (59.1%), whereas the rate was lowest for those who did not continue cannabis use (28.5%). Among intermittent users, the relapse rate was 36.0%.
These results reveal a dose-dependent association between change in cannabis use and relapse of psychosis that is unlikely to be a result of self-medication or genetic and environmental confounding.
Understanding the nature of the association between cannabis use and psychotic disorders is crucial for the formulation of evidence-based health policies concerning cannabis,” the researchers write.
This understanding is particularly important because psychotic disorders, such as schizophrenia, cause the most severe health loss of all human disorders and are associated with considerable financial burden.
Psychotic disorders are also associated with a high rate of comorbid abuse of cannabis, the most commonly used illicit drug worldwide.
Schoeler T, Petros N, Di Forti M, et al. Association Between Continued Cannabis Use and Risk of Relapse in First-Episode Psychosis: A Quasi-Experimental Investigation Within an Observational Study. JAMA Psychiatry. Published online September 28, 2016. doi:10.1001/jamapsychiatry.2016.2427.