Abstract
BACKGROUND: First episode psychosis (FEP) patients who use cannabis experience more frequent psychotic and euphoric intoxication experiences compared to controls. It is not clear whether this is consequent to patients being more vulnerable to the effects of cannabis use or to their heavier pattern of use. We aimed to determine whether extent of use predicted psychotic-like and euphoric intoxication experiences in patients and controls and whether this differs between groups.
METHODS: We analysed data on patients who had ever used cannabis (n = 655) and controls who had ever used cannabis (n = 654) across 15 sites from six countries in the EU-GEI study (2010-2015). We used multiple regression to model predictors of cannabis-induced experiences and to determine if there was an interaction between caseness and extent of use.
RESULTS: Caseness, frequency of cannabis use and money spent on cannabis predicted psychotic-like and euphoric experiences (p ⩽ 0.001). For psychotic-like experiences (PEs) there was a significant interaction for caseness × frequency of use (p < 0.001) and caseness × money spent on cannabis (p = 0.001) such that FEP patients had increased experiences at increased levels of use compared to controls. There was no significant interaction for euphoric experiences (p > 0.5).
CONCLUSIONS: FEP patients are particularly sensitive to increased psychotic-like, but not euphoric experiences, at higher levels of cannabis use compared to controls. This suggests a specific psychotomimetic response in FEP patients related to heavy cannabis use. Clinicians should enquire regarding cannabis related PEs and advise that lower levels of cannabis use are associated with less frequent PEs.
| Original language | English |
|---|---|
| Pages (from-to) | 2074 - 2082 |
| Journal | Psychological Medicine |
| Volume | 51 |
| Issue number | 12 |
| Early online date | 28 Apr 2020 |
| DOIs | |
| Publication status | Published - 30 Sept 2021 |
Funding
Financial support. This work was supported by the European Community’s Seventh Framework Programme under grant agreement No. HEALTH-F2-2010-241909 (Project EU-GEI). The Brazilian study was funded by the São Paulo Research Foundation under grant number 2012/0417-0. The funder was not involved in design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the manuscript, and decision to submit the manuscript for publication. Dr Marta Di Forti is funded by the Medical Research Council. Dr Sami was supported by a Medical Research Council Clinical Research Training Fellowship (MR/ P001408/1). Dr Freeman was supported by a Senior Academic Fellowship from the Society for the Study of Addiction. Dr Marta Di Forti and Dr Musa Sami had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analyses.