Cannabis Use and the Incidence of Psychotic Disorders

What should we consider before prescribing medicinal cannabis?

Marta Di Forti - MD, PhD. 

Cannabis is used daily by some 200 million people worldwide, and its use and potency have increased in many countries; for example, my group has shown that high-potency types have taken over 96% of the London “street” market. Furthermore, the spread of laws legalizing cannabis for medicinal or recreational use has been accompanied by more relaxed attitudes towards cannabis. Cross-sectional and prospective epidemiological studies, as well as biological investigations, demonstrate a causal link between cannabis use and psychotic disorder, especially of a paranoid type. Furthermore, our research has shown a) a dose-response association with the highest odds of psychotic disorder in the heaviest cannabis users, b) high potency types carry the greatest risk for psychotic disorder, c) patterns of cannabis use have a major impact on the incidence of psychotic disorder across Europe. High-potency cannabis types have high concentrations of delta-9-tetrahydrocannabinol (THC) and virtually no cannabidiol (CBD), which, in experimental studies of healthy volunteers ameliorates the psychotogenic effect of THC. A minority of cannabis users develop clinical psychosis, but it is unclear what proportion of heavy users develop minor psychotic symptoms and paranoia in particular. Therefore, in this talk, I shall present the above evidence and discuss how they might inform how and if we can move to safely prescribe cannabis for medicinal use.

Video link: https://vimeo.com/683812459/e1f203a6ab

Speaker Details

Full Name
Marta Di Forti

Institution
MD, PhD

Bio
Dr Marta Di Forti is a Senior Lecturer at the Dept of Social, Developmental and Genetic Research, Institute of Psychiatry, and Honorary Consultant Adult Psychiatrist, Lambeth Community team, South London and Maudsley NHS foundation Trust. She leads the first and only Cannabis Clinic for patients with Psychotic disorders in the UK. She was recently awarded a MRC Senior Research Fellowship to expand her research in the role of cannabis use in psychosis and its underlying biology. With her team she showed for the first time that the use of high-potency types of cannabis e.g. "skunk" carries a higher risk of psychosis than use of traditional types and that it affects rates of Psychotic disorders across Europe. Though it still remains unclear who are those cannabis users most at risk. Her future work aims to investigate the interaction between cannabis use and genes predisposing to schizophrenia, and how cannabis changes the epigenome.