Smoking cannabis has negative effects on human health
Substantial scientific literature, including systematic reviews and meta-analyses, supports the claim that smoking or consuming cannabis has negative effects on human health, ranging from cognitive impairment and cardiovascular risks to adverse pregnancy outcomes and increased risk of psychosis.
The claim is specific and empirical. Multiple high-quality systematic reviews, meta-analyses, and umbrella reviews provide robust evidence that cannabis use carries various adverse health effects, including cognitive deficits, mental health risks (such as psychosis), cardiovascular events, and complications during pregnancy. No papers refute the broad claim that cannabis has negative effects on some aspects of human health, though studies note that safety profiles vary by dosage, potency, and route of administration.
BIANCA CALABRIA, LOUISA DEGENHARDT, WAYNE HALL, MICHAEL LYNSKEY. Does cannabis use increase the risk of death? Systematic review of epidemiological evidence on adverse effects of cannabis use. 2010. https://doi.org/10.1111/j.1465-3362.2009.00149.x
Calabria et al. (2010) found evidence suggesting adverse health outcomes, such as fatal motor vehicle accidents and respiratory or brain cancers, among heavy cannabis users.
See more details
Laura Dellazizzo, S. Potvin, S. Giguère, A. Dumais. Evidence on the acute and residual neurocognitive effects of cannabis use in adolescents and adults: a systematic meta-review of meta-analyses.. 2022. https://doi.org/10.1111/add.15764
A systematic meta-review by a research group in 2022 demonstrated that acute cannabis intoxication and residual use lead to small-to-moderate neurocognitive and memory deficits.
Jamie O Lo, Chelsea K. Ayers, Snehapriya Yeddala, Beth Shaw, Shannon Robalino, Rachel Ward, D. Kansagara. Prenatal Cannabis Use and Neonatal Outcomes: A Systematic Review and Meta-Analysis.. 2025. https://doi.org/10.1001/jamapediatrics.2025.0689
A 2025 systematic review and meta-analysis found moderate-certainty evidence linking prenatal cannabis use to adverse neonatal outcomes like low birth weight and preterm birth.
Mariana M Prete, G. Feitosa, M. A. Ribeiro, T. M. Fidalgo, Zila M. Sanchez. Adverse clinical effects associated with the use of synthetic cannabinoids: A systematic review.. 2025. https://doi.org/10.1016/j.drugalcdep.2025.112698
A 2025 systematic review highlighted severe clinical outcomes associated with synthetic cannabinoids, including psychosis, seizures, and cardiovascular complications.
Wilhelm Storck, Meyer Elbaz, Cécile Vindis, Amélia Déguilhem, Maryse Lapeyre-Mestre, Emilie Jouanjus. Cardiovascular risk associated with the use of cannabis and cannabinoids: a systematic review and meta-analysis.. 2025. https://doi.org/10.1136/heartjnl-2024-325429
A 2025 systematic review and meta-analysis revealed positive associations between cannabis use and major adverse cardiovascular events, including acute coronary syndrome and stroke.
Marco Solmi, Marco De Toffol, Jong Yeob Kim, Min Je Choi, Brendon Stubbs, Trevor Thompson, Joseph Firth, Alessandro Miola, Giovanni Croatto, Francesca Baggio, Silvia Michelon, Luca Ballan, Björn Gerdle, Francesco Monaco, Pierluigi Simonato, Paolo Scocco, Valdo Ricca, Giovanni Castellini, Michele Fornaro, Andrea Murru, Eduard Vieta, Paolo Fusar-Poli, Corrado Barbui, John P A Ioannidis, Andrè F Carvalho, Joaquim Radua, Christoph U Correll, Samuele Cortese, Robin M Murray, David Castle, Jae Il Shin, Elena Dragioti. Balancing risks and benefits of cannabis use: umbrella review of meta-analyses of randomised controlled trials and observational studies.. 2023. https://doi.org/10.1136/bmj-2022-072348
An umbrella review from 2023 reported convincing evidence that cannabis causes psychotic symptoms, impairs cognition, increases car crash risks, and worsens outcomes in pregnancy.
Penny F Whiting, Robert F Wolff, Sohan Deshpande, Marcello Di Nisio, Steven Duffy, Adrian V Hernandez, J Christiaan Keurentjes, Shona Lang, Kate Misso, Steve Ryder, Simone Schmidlkofer, Marie Westwood, Jos Kleijnen. Cannabinoids for Medical Use: A Systematic Review and Meta-analysis.. 2015. https://doi.org/10.1001/jama.2015.6358
A 2015 systematic review found that cannabis and cannabinoids were associated with an increased risk of short-term adverse events such as dizziness, confusion, and hallucinations.
Kat Petrilli, Shelan Ofori, Lindsey Hines, Gemma Taylor, Sally Adams, Tom P Freeman. Association of cannabis potency with mental ill health and addiction: a systematic review.. 2022. https://doi.org/10.1016/S2215-0366(22)00161-4
A 2022 systematic review concluded that the use of higher-potency cannabis is associated with an increased risk of psychosis and cannabis use disorder.
The paper trail · every fact has a biography
Challenge the receipt
Citation formatting by citeproc-js (Frank Bennett) and the Citation Style Language project. Source and licenses.
Terms · Privacy · How verdicts work · Dispute this receipt