What stroke is
A stroke is a medical emergency in which the blood supply to part of the brain is interrupted. There are two main types. Ischaemic stroke — about 85% of UK cases — is caused by a blood clot blocking an artery supplying the brain. Haemorrhagic stroke — about 15% — is caused by a burst blood vessel bleeding into or around the brain. A transient ischaemic attack (TIA), sometimes called a mini-stroke, produces stroke-like symptoms that resolve within 24 hours because the blockage is temporary.
In the UK, around 100,000 people have a stroke each year. It is the fourth single leading cause of death and the largest cause of complex disability. Treatment for acute ischaemic stroke includes thrombolysis (clot-dissolving medication) and mechanical thrombectomy (physical clot removal), both of which must be delivered within hours of symptom onset. Long-term management focuses on secondary prevention (blood pressure control, antiplatelet or anticoagulant medication, cholesterol reduction, lifestyle changes) and rehabilitation.
The research on cannabis and stroke divides into two distinct questions: whether cannabis use affects the risk of having a stroke (prevention and risk), and whether cannabinoids could be used to treat or protect the brain during or after a stroke (acute treatment and neuroprotection). These two lines of evidence point in opposite directions and must not be conflated.
Cannabis research on Stroke
Prevention and risk: cannabis and stroke occurrence
A 2011 prospective study by Wolff and colleagues examined cannabis use and ischaemic stroke in 48 consecutive young patients (aged 18-45) admitted to a single stroke unit (prospective observational study, n=48). The study found evidence of multifocal intracranial vasoconstriction — narrowing of multiple brain arteries — in cannabis users who presented with ischaemic stroke. The authors concluded that cannabis use may be a risk factor for ischaemic stroke in young people through a mechanism of reversible cerebral vasoconstriction.
A 2016 case-control study by Rumalla and colleagues compared cannabis use among patients with ischaemic stroke or TIA against matched controls. It found a significant association between cannabis use and stroke or TIA after adjustment for confounders. Some patients experienced recurrent stroke or TIA after cannabis re-exposure, which strengthens but does not prove a causal link.
A 2017 review by Wolff and Jouanjus evaluated the role of cannabinoids (cannabis and synthetic cannabinoids) in stroke occurrence (narrative review). It concluded that cannabis and synthetic cannabinoid use should be considered as potential contributors to stroke in young adults presenting without conventional vascular risk factors. The review described proposed mechanisms including reversible cerebral vasoconstriction, cardiac arrhythmia, and systemic hypotension.
A 2014 review by Thomas and colleagues in the Journal of the American College of Cardiology examined adverse cardiovascular, cerebrovascular, and peripheral vascular effects of marijuana inhalation (narrative review). It summarised case reports, case series, and population-based studies linking cannabis use to stroke, myocardial infarction, and peripheral vascular events, and advised that cardiologists should be aware of these associations.
Acute treatment and neuroprotection
A 2007 study by Degn and colleagues measured changes in brain levels of N-acylethanolamines (NAEs) and 2-arachidonoylglycerol (2-AG) in mice after permanent middle cerebral artery occlusion, a model of focal cerebral ischaemia (animal study). The study found time-dependent increases in several NAEs and 2-AG in the ischaemic brain tissue during the first 24 hours after stroke induction. The finding describes an endogenous brain response to injury; it does not show that administering cannabinoids after a stroke improves outcomes.
A 2025 study by de Souza Stork and colleagues tested a full-spectrum Cannabis sativa extract in a rat model of ischaemic stroke (animal study, 2025). The extract was administered after stroke induction. The authors reported improvements in neurological deficits, reductions in blood immune cells, lymphoid organ atrophy, and corticosterone levels, and protection against gut permeability, oxidative stress, and lung inflammation. These are post-stroke systemic effects in rats. The study does not constitute human evidence, and it did not test whether the extract reduced infarct size or improved long-term functional recovery.
No human clinical trial has tested a cannabinoid as an acute stroke treatment or for post-stroke neuroprotection.
Compounds studied for Stroke
THC is the cannabinoid most consistently implicated in the case reports and observational studies linking cannabis use to stroke in young adults. The proposed mechanism — reversible cerebral vasoconstriction — is a plausible but unproven pathway. THC has also been studied in animal models of neuroprotection after brain injury, with mixed results depending on dose, timing, and model. No human trial has tested THC as a stroke treatment.
CBD has been studied in animal models of cerebral ischaemia for its anti-inflammatory, antioxidant, and neuroprotective properties. These are animal data. No human RCT has tested CBD for acute stroke or post-stroke recovery.
CBG has no published research on stroke prevention or treatment. Its receptor profile (alpha-2 adrenergic agonist, TRP channel modulation) provides a plausible mechanistic basis for investigation, but this is entirely speculative for stroke.
Borneol is a terpene found in cannabis that has been studied in traditional Chinese medicine as a component of stroke treatments. This is drug-delivery research, not evidence that borneol or cannabis affects stroke outcomes.
Beta-caryophyllene is a CB2 receptor agonist. CB2 activation has been studied in animal models of cerebral ischaemia for anti-inflammatory effects. No human stroke trial of beta-caryophyllene exists.
Pinene has been studied for its anti-inflammatory properties in cell and animal models. No human stroke trial of pinene exists.
Limits of the evidence for Stroke
What the evidence establishes
Observational studies consistently report an association between cannabis use and ischaemic stroke in young adults, including findings of multifocal intracranial vasoconstriction on brain imaging. This association has been reported in prospective studies, case-control studies, and case series.
The endocannabinoid system responds to cerebral ischaemia: levels of protective endocannabinoid-related lipids increase in ischaemic brain tissue in animal models. This is a physiological finding, not a treatment.
Cannabinoid administration after experimental stroke in rodents has produced reductions in neurological deficits, inflammation, and systemic organ damage in some animal studies.
What the evidence does not establish
That cannabis prevents stroke. The observational evidence points towards an elevated short-term risk, not a protective effect.
That cannabinoids can be used to treat acute stroke. No human clinical trial has tested this. The animal evidence is preliminary and has not been replicated in a human population.
That cannabis is safe for people who have had a stroke or TIA, or for people at elevated risk of stroke. The association between cannabis use and stroke in young adults, including recurrent events after re-exposure, is a safety signal that has not been resolved.
That a specific cannabinoid or terpene ratio modifies stroke risk or improves post-stroke recovery. No data exist to support such a claim.
That cannabis or cannabinoids can be used for post-stroke spasticity or pain. While nabiximols (THC:CBD oromucosal spray) is licensed in the UK for spasticity in multiple sclerosis, it has not been tested in an RCT for post-stroke spasticity. The evidence does not transfer from MS to stroke.
Whether the vasoconstrictive effects observed in young adult cannabis users are dose-dependent, duration-dependent, or route-dependent is unknown. Whether they apply to isolated CBD, which has different vascular effects from THC, is also unknown.
Related conditions
- Alzheimer’s and dementia ; preclinical neuroprotection research
- Diabetes and metabolic health ; observational data on glucose, insulin, and body weight
- Chronic pain (NICE context) ; the evidence behind NICE guideline NG144
- ALS/Motor neuron disease ; early research on spasticity and symptom control
Read next
- CBD ; examined for neuroprotective effects in preclinical stroke models
- THC ; studied in preclinical models of cerebral ischaemia
- Browse the cannabinoid reference
- Browse the terpene reference
Sources
1. Wolff V, Lauer V, Rouyer O, et al. Cannabis use, ischemic stroke, and multifocal intracranial vasoconstriction: a prospective study in 48 consecutive young patients. Stroke. 2011;42(6):1778-1780. doi:10.1161/STROKEAHA.110.610915. PMID: 21546468. Study record
2. Rumalla K, Reddy AY, Mittal MK. Association of recreational marijuana use with stroke and transient ischemic attack. J Stroke Cerebrovasc Dis. 2016;25(12):2862-2867. doi:10.1016/j.jstrokecerebrovasdis.2016.08.006. PMID: 27618187. Study record
3. Wolff V, Jouanjus E. Strokes are possible complications of cannabinoids use. Epilepsy Behav. 2017;70(Pt B):355-363. doi:10.1016/j.yebeh.2017.01.031. PMID: 28216042. Study record
4. Thomas G, Kloner RA, Rezkalla S. Adverse cardiovascular, cerebrovascular, and peripheral vascular effects of marijuana inhalation: what cardiologists need to know. Am J Cardiol. 2014;113(1):187-190. doi:10.1016/j.amjcard.2013.09.042. PMID: 24176069. Study record
5. Degn M, Lambertsen KL, Petersen G, et al. Changes in brain levels of N-acylethanolamines and 2-arachidonoylglycerol in focal cerebral ischemia in mice. J Neurochem. 2007;103(4):1609-1620. doi:10.1111/j.1471-4159.2007.04878.x. PMID: 17725580. Study record
6. de Souza Stork S, Mathias K, Gava F, et al. Full-spectrum Cannabis sativa extract enhances gut-peripheral organ integrity after experimental ischemic stroke. Inflammopharmacology. 2025;33(2):749-764. doi:10.1007/s10787-024-01627-6. PMID: 39888505. Study record
