Recipient organisationNIHR Maudsley Biomedical Research Centre
NIHR supportRecorded as supported by this research centre
PeriodFeb 2025 — Ongoing
In plain English
AI plain-English summary
Cannabis use is linked to roughly 30% of new psychosis cases in South London, and 80% of patients admitted to psychiatric intensive care units are cannabis users. This matters because psychotic illnesses cost England at least £12 billion annually, and cannabis is one of the few modifiable risk factors. Yet researchers do not fully understand how cannabis acts on the brain’s endocannabinoid system to trigger or worsen psychosis, aggression, and violence. As social attitudes shift toward legalising recreational cannabis, understanding this biological mechanism becomes urgent. If this research succeeds, it could change how clinicians identify people most vulnerable to cannabis-induced psychosis—potentially through biological markers. It could also inform primary prevention strategies to reduce new psychosis cases, and secondary prevention to better manage violence in psychiatric intensive care units, reducing hospital admissions and long-term distress. The findings would directly affect clinical practice and public health policy, not everyday consumer behaviour. This is applied biomedical research with clear, near-term implications for how the NHS treats psychosis and manages risk.
View original technical description
Psychotic illnesses are a significant cause of disability and account for a financial burden of at least £12 billion annually in England. It is of public health relevance to identify risk factors for targeted interventions. Cannabis is the most used illicit substance worldwide and is one of the major modifiable risk factors for developing a first episode of psychosis (FEP). Indeed, it has been estimated that 30% of new cases of psychosis in South London may be Moreover, using cannabis has been associated with more severe symptoms at FEP and a higher risk of aggression and violent incidents. Indeed, individuals using cannabis are more likely to require admission to a psychiatric intensive care unit (PICU) to contain and manage risks to themselves and others. Among all patients admitted to PICU, about 80% are cannabis users. Continuing to use cannabis after an FEP is also associated with worse long-term symptoms and functional outcomes, including a higher risk of hospital admissions. Notably, the current social attitude toward legalising cannabis for recreational use makes it vital to examine how cannabis impacts the brain's functioning in psychosis. Therefore, this study aims to investigate the biological system on which cannabis acts in the brain, namely the endocannabinoid system, in patients admitted to Hospital who present with psychosis, violence and aggression. Findings from this project may inform the academic, clinical, and public communities on the public health relevance of cannabis use and primary prevention of psychosis, violence and aggression. They may also provide support in developing secondary prevention strategies on how to manage violence in PICU better and prevent hospital admissions and long-term distressing consequences. Finally, findings may provide insight into potential biological markers explaining why some people are more vulnerable to the psychotropic effects of cannabis and psychosis exacerbations.
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