Molecular brain differences and cannabis involvement: A systematic review of positron emission tomography studies.
Hui Xu, Max M Owens, Troy Farncombe, Michael D Noseworthy, James MacKillop
Journal of Psychiatric Research June 2023 DOI: 10.1016/j.jpsychires.2023.03.045 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Systematic review Peer reviewed |
|---|---|
| Population | Individuals who use cannabis or have cannabis use disorder |
| Topics | Cannabis |
| Keywords | Cannabis use disorder Dopamine Endocannabinoid system Positron emission tomography |
| Key findings | Across 20 PET studies, cannabis use was associated with abnormal striatal dopamine synthesis capacity correlated with clinical symptoms, lower cannabinoid receptor type 1 availability and global reductions in fatty acid amide hydrolase binding, and lower normalized glucose metabolism in cortical and subcortical regions plus reduced lateral prefrontal cerebral blood flow during tasks. The authors note very high heterogeneity across studies and that whether these differences are causal or consequential is largely unclear. |
Abstract
An increasing number of studies have used positron emission tomography (PET) to investigate molecular neurobiological differences in individuals who use cannabis. This study aimed to systematically review PET imaging research in individuals who use cannabis or have cannabis use disorder (CUD). Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria, a comprehensive systematic review was undertaken using the PubMed, Scopus, PsycINFO and Web of Science databases. In total, 20 studies were identified and grouped into three themes: (1) studies of the dopamine system primarily found that cannabis use was associated with abnormal striatal dopamine synthesis capacity, which was in turn correlated with clinical symptoms; (2) studies of the endocannabinoid system found that cannabis use and CUD are associated with lower cannabinoid receptor type 1 availability and global reductions in fatty acid amide hydrolase binding; (3) studies of brain metabolism found that individuals who use cannabis exhibit lower normalized glucose metabolism in both cortical and subcortical brain regions, and reduced cerebral blood flow in the lateral prefrontal cortex during experimental tasks. Heterogeneity across studies prevented meta-analysis. Existing PET imaging research reveals substantive molecular differences in cannabis users in the dopamine and endocannabinoid systems, and in global brain metabolism, although the heterogeneity of designs and approaches is very high, and whether these differences are causal versus consequential is largely unclear.
Comparable studies
Other systematic reviews and meta-analyses on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Effects of cannabis use on outcomes of psychotic disorders: systematic review People with psychotic disorders, as examined in 13 longitudinal studies | 2008 | Systematic review | |
| The Impact of Cannabis Use on Cognitive Functioning in Patients With Schizophrenia: A Meta-analysis of Existing Findings and New Data in a First-Episode Sample Patients with established schizophrenia (meta-analysis: 572) and patients with... | 2010 | Meta-analysis and cross-sectional observational study | n = 700 |
| Medicinal cannabis for psychiatric disorders: a clinically-focused systematic review | 2020 | Systematic review | |
| Neuroimaging in cannabis use: a systematic review of the literature Cannabis users and controls in neuroimaging studies | 2009 | Systematic review | |
| Human Laboratory Studies on Cannabinoids and Psychosis. Healthy human subjects and individuals with schizophrenia | 2016 | Systematic review |
Citations in the library
Cited by 3
- The role of subcortical brain tissue iron as an indicator of dopamine neurophysiology in adolescent cannabis use. Neuropsychopharmacology June 2, 2026
- Increased Mesostriatal Intrinsic Connectivity Associated With Cue Exposure in Adult Cannabis Users: Preliminary Findings. Addiction Biology August 1, 2025
- Convergence of Cannabis and Psychosis on the Dopamine System JAMA Psychiatry April 9, 2025
Cites 7
- Dynamic coupling of whole-brain neuronal and neurotransmitter systems Proceedings of the National Academy of Sciences April 13, 2020
- The neuropsychopharmacology of cannabis: A review of human imaging studies Pharmacology & Therapeutics October 20, 2018
- Dopamine release in chronic cannabis users: a [11c]raclopride positron emission tomography study. Biological Psychiatry April 15, 2012
- Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers Molecular Psychiatry July 12, 2011
- Neural substrates of faulty decision-making in abstinent marijuana users. Neuroimage June 2005
and 2 more in the library