International Journal of Neuropsychopharmacology
September 9, 2026
M Di Forti, I Austin-Zimmerman, E Spinazzola et al.
Abstract Background Epidemiological data have consistently shown an association between heavy cannabis use and increased risk of psychotic disorders. Nevertheless, not all cannabis users develop the illness. Evidence from other substance of abuse such as Alcohol suggest how genetic differences in enzymes involved in its metabolism influence individual response to the drug. No studies to data...
Frontiers in Psychiatry
July 21, 2026
Kenneth P. Finn, Robin Murray, Elizabeth Stuyt et al.
Cannabis is one of the most widely used psychoactive substances, with higher use rates in countries that have implemented policies to legalize medical or recreational use. Following the development of cannabis products with concentrations well above 10% THC (high potency, delta-9 tetrahydrocannabinol), the number of psychosis cases has also increased. Cannabis-attributable psychosis cases...
Biological Psychiatry Global Open Science
May 13, 2026
I. Austin-Zimmerman, Qiang Li, E. Johnson et al.
Background Cannabis use is associated with increased risk of psychotic disorders, but the underlying biological mechanisms remain unclear. We used genetic data to investigate the molecular pathways contributing to the association between cannabis use disorder (CUD) and psychosis. Methods We conducted a cross-disorder meta-analysis of genome-wide association studies (GWASs) on schizophrenia and...
Psychological Medicine
August 8, 2025
Giulia Trotta, Edoardo Spinazzola, Hannah Degen et al.
4 citations
Childhood trauma is a well-established risk factor for psychosis, paranoia, and substance use, with cannabis being a modifiable environmental factor that exacerbates these vulnerabilities. This study examines the interplay between childhood trauma, cannabis use, and paranoia using standard tetrahydrocannabinol (THC) units as a comprehensive measure of cannabis exposure. Data were derived from...
Psychological Medicine
May 4, 2023
Giulia Trotta, Victoria Rodriguez, Diego Quattrone et al.
Abstract Background Childhood adversity and cannabis use are considered independent risk factors for psychosis, but whether different patterns of cannabis use may be acting as mediator between adversity and psychotic disorders has not yet been explored. The aim of this study is to examine whether cannabis use mediates the relationship between childhood adversity and psychosis. Methods Data were...
Cannabis and Cannabinoid Research
December 9, 2022
Lucy Chester, Amir Englund, Edward Chesney et al.
20 citations
Background: The effects of cannabis are thought to be mediated by interactions between its constituents and the endocannabinoid system. Delta-9-tetrahydrocannabinol (THC) binds to central cannabinoid receptors, while cannabidiol (CBD) may influence endocannabinoid function without directly acting on cannabinoid receptors. We examined the effects of THC coadministered with different doses of CBD...
World Journal of Biological Psychiatry
March 22, 2022
Deepak C. D’Souza, M. Diforti, Suhas Ganesh et al.
Abstract Objectives The liberalisation of cannabis laws, the increasing availability and potency of cannabis has renewed concern about the risk of psychosis with cannabis. Methods The objective of the WFSBP task force was to review the literature about this relationship. Results Converging lines of evidence suggest that exposure to cannabis increases the risk for psychoses ranging from...
Translational Psychiatry
August 10, 2021
Diego Quattrone, Ulrich Reininghaus, A. Richards et al.
Diagnostic categories do not completely reflect the heterogeneous expression of psychosis. Using data from the EU-GEI study, we evaluated the impact of schizophrenia polygenic risk score (SZ-PRS) and patterns of cannabis use on the transdiagnostic expression of psychosis. We analysed first-episode psychosis patients (FEP) and controls, generating transdiagnostic dimensions of psychotic symptoms...
Psychological Medicine
March 18, 2020
Diego Quattrone, Laura Ferraro, Giada Tripoli et al.
89 citations
Abstract Background Daily use of high-potency cannabis has been reported to carry a high risk for developing a psychotic disorder. However, the evidence is mixed on whether any pattern of cannabis use is associated with a particular symptomatology in first-episode psychosis (FEP) patients. Method We analysed data from 901 FEP patients and 1235 controls recruited across six countries, as part of...
Journal of Psychopharmacology
October 5, 2012
Amir Englund, Paul D. Morrison, Judith Nottage et al.
463 citations
Community-based studies suggest that cannabis products that are high in Δ⁹-tetrahydrocannabinol (THC) but low in cannabidiol (CBD) are particularly hazardous for mental health. Laboratory-based studies are ideal for clarifying this issue because THC and CBD can be administered in pure form, under controlled conditions. In a between-subjects design, we tested the hypothesis that pre-treatment...
Frontiers in Behavioral Neuroscience
2011
Alessandra Paparelli, Marta Di Forti, Paul D. Morrison et al.
217 citations
The prevalent view today is that schizophrenia is a syndrome rather than a specific disease. Liability to schizophrenia is highly heritable. It appears that multiple genetic and environmental factors operate together to push individuals over a threshold into expressing the characteristic clinical picture. One environmental factor which has been curiously neglected is the evidence that certain...
The British Journal of Psychiatry
November 30, 2009
Marta Di Forti, Craig Morgan, Paola Dazzan et al.
577 citations
BACKGROUND: People who use cannabis have an increased risk of psychosis, an effect attributed to the active ingredient Delta 9-tetrahydrocannabinol (Delta 9-THC). There has recently been concern over an increase in the concentration of Delta 9-THC in the cannabis available in many countries. AIMS: To investigate whether people with a first episode of psychosis were particularly likely to use...
Schizophrenia Bulletin
November 1, 2008
Cécile Henquet, Marta Di Forti, Paul D. Morrison et al.
Cannabis use is considered a contributory cause of schizophrenia and psychotic illness. However, only a small proportion of cannabis users develop psychosis. This can partly be explained by the amount and duration of the consumption of cannabis and by its strength but also by the age at which individuals are first exposed to cannabis. Genetic factors, in particular, are likely to play a role in...
European Psychiatry
June 1, 2005
Anton Grech, Jim Van Os, Peter B. Jones et al.
AbstractPurposeTo test the hypothesis that recent onset psychotic patients who use cannabis will have psychotic symptoms that are more severe and more persistent than those who do not use cannabis.Subjects and methodsWe carried out a 4-year follow-up study of a cohort of 119 patients with recent onset of psychosis. The patients were divided into four groups according to duration of cannabis...
The British Journal of Psychiatry
January 30, 2004
Louise Arseneault, Mary Cannon, John Witton et al.
924 citations
BACKGROUND: Controversy remains as to whether cannabis acts as a causal risk factor for schizophrenia or other functional psychotic illnesses. AIMS: To examine critically the evidence that cannabis causes psychosis using established criteria of causality. METHOD: We identified five studies that included a well-defined sample drawn from population-based registers or cohorts and used prospective...
Schizophrenia Research
September 1, 1994
Philip Mcguire, P Jones, I Harvey et al.
The Present State Examination was used to assess the psychopathology of 23 psychotic patients who were cannabis positive on urinary screening, and 46 matched drug-free controls. Cases and controls were indistinguishable in terms of psychopathology, DSMIII diagnoses, onset of recent illness, the proportion of first admissions, ethnicity, and socio-economic class, differing only in their...
The British journal of psychiatry : the journal of mental science
September 1980
S A Checkley, R M Murray, M C Oon et al.
The excretion of N,N,-dimethyltryptamine (DMT) has been measured in longitudinal studies of five patients with schizophrenic illnesses and in four patients with rapidly or slowly cycling manic-depressive illness. The excretion of DMT was frequently raised in patients when they were psychotic but was usually normal when they had recovered. However, rapid changes in the severity of illness or...
Psychological Medicine
February 1, 1977
R. Rodnight, Robin Murray, M. C. H. Oon et al.
33 citations
SynopsisThe excretion of dimethyltryptamine (DMT) was studied amongst 122 recently admitted psychiatric patients and 20 normal subjects. DMT was detected in the urine of 47% of those diagnosed by their psychiatrists as schizophrenic, 38% of those with other non-affective psychoses, 13% of those with affective psychoses, 19% of those with neurotic and personality disorders and 5% of normal...
Uri Bright, Suhas Ganesh, Daniel F. Levey et al.
Abstract Background Cannabis is one of the most widely used psychoactive substances worldwide. Δ 9 -tetrahydrocannabinol (Δ 9 -THC) is the main contributor to cannabis-induced effects such as euphoria, anxiety, and psychotomimetic effects, and is metabolized by several hepatic enzymes, including CYP3A4. There are interindividual differences in how cannabis affects users, which have substantial...