A large analysis led by researchers at the University of Cambridge has reported that people who use cannabis, cocaine or amphetamines show measurably higher rates of stroke, including among adults who are still relatively young. The work pooled data from published cohort studies covering more than 100 million participants, and it found that cannabis use was associated with roughly a 37 percent increase in stroke risk. The figure describes a statistical association observed across many studies rather than a demonstrated cause in any single person, and the authors were careful to separate the two ideas.
Stroke ranks among the most consequential health problems worldwide, sitting near the top of the combined list of causes of death and long-term disability. Many of the conditions that raise stroke risk, such as high blood pressure, diet and physical inactivity, can be modified through behavior, and the new work adds recreational drug use to the set of factors researchers are examining closely.
Combining published cohorts into one meta-analysis
The team from the Cambridge Department of Clinical Neurosciences conducted a systematic review and meta-analysis, a method that combines results from multiple published cohort studies so that patterns too small to detect in any single dataset can emerge from the pooled total. Earlier evidence linking recreational drugs to stroke had been inconsistent, partly because much of it was observational and varied in quality, and the pooling approach was designed to produce a firmer estimate. The findings were published in the International Journal of Stroke, where the full systematic review and Mendelian randomization analysis lays out the underlying figures.
What the 37 percent figure describes
Across the pooled studies, cannabis use was associated with about a 37 percent higher likelihood of stroke. That is a relative increase applied to an individual’s baseline risk, not a statement that more than a third of cannabis users will have a stroke. The same analysis found sharper associations for other substances, with cocaine linked to a 96 percent increase and amphetamines to a 122 percent increase, each roughly doubling the estimated risk. Opioid use, by contrast, showed no statistically significant association with stroke in the combined data.
A closer look at users under 55
The researchers examined younger adults separately because stroke in people under 55 is comparatively unusual and often prompts a search for specific triggers. Within that group, amphetamine use was associated with nearly three times the risk of stroke, an increase of about 174 percent. Cocaine remained associated with a large increase of about 97 percent, while cannabis was tied to a smaller 14 percent rise in the younger cohort. The pattern suggests the substances may weigh differently depending on age and stroke subtype.
Testing whether the link is causal
To move beyond association, the team applied Mendelian randomization, a technique that uses naturally occurring genetic variants tied to a behavior or risk factor to test whether that factor plausibly causes an outcome. The genetic analysis indicated that cocaine use disorders were particularly associated with brain hemorrhage and cardioembolic stroke, in which a clot forming in the heart travels to the brain. Cannabis use disorders were associated with stroke overall and especially with large artery stroke. According to the researchers, those genetic findings support the possibility of a causal relationship rather than an association alone, though they could not run the same genetic test for amphetamines because sufficiently large datasets on amphetamine use do not yet exist.
Biological pathways that could explain the pattern
Several known mechanisms could connect these drugs to stroke. The researchers point to sudden spikes in blood pressure, spasms and narrowing of blood vessels, abnormal heart rhythms, increased blood clotting that they associate especially with cannabis, and inflammation or vasculitis that they associate especially with amphetamines. All of those processes already feature in the standard understanding of how strokes occur, whether ischemic strokes caused by blocked blood flow or hemorrhagic strokes caused by bleeding. Problematic alcohol use was also linked in the analysis to a greater risk of cardioembolic and large artery stroke.
How common use is, and why the finding matters
Recreational drug use is widespread enough that even a moderate shift in risk can matter at the population level. The study noted that in 2024, about 8.8 percent of adults aged 16 to 59 in England and Wales, roughly 2.9 million people, reported using a recreational drug in the previous year, while recent United States data indicate that more than half of people over age 12 have used substances such as cocaine, cannabis or opiates at least once. Public health agencies, including the U.S. Centers for Disease Control and Prevention, describe stroke as a leading cause of serious long-term disability and emphasize modifiable risk factors.
What the researchers say the results support
Megan Ritson of the Cambridge Stroke Research Group described the work as the most comprehensive analysis yet conducted on recreational drug use and stroke, arguing that it strengthens the evidence that these drugs act as causal risk factors. Eric Harshfield, an Alzheimer’s Society Research Fellow in the department, said the analysis suggests the drugs themselves raise risk rather than merely reflecting other lifestyle patterns among people who use them. The team framed the takeaway around public health measures to reduce substance use as one route to lowering stroke rates. The full summary of the Cambridge findings notes that the project was funded by the British Heart Foundation with additional support from the National Institute for Health and Care Research Cambridge Biomedical Research Center.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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