Using Cannabis Could Raise Your Stroke Risk by 37%, Massive Study Reveals

Large-scale evidence suggests cannabis, cocaine, and amphetamines may directly raise stroke risk, including in younger adults.

As recreational drug use becomes increasingly common, researchers are uncovering evidence that its health consequences may extend far beyond addiction and overdose. A Cambridge-led study analyzing data from more than 100 million people has found that cannabis, cocaine, and amphetamines are linked to a significantly higher risk of stroke, with some of the strongest effects seen in younger adults.

Stroke is the world's third leading cause of death and disability combined, yet many of its risk factors are considered preventable. While high blood pressure, smoking, and poor diet are well-established contributors, scientists have increasingly questioned whether commonly used recreational drugs may also play a direct role.

In 2024, around 2.9 million adults aged 16 to 59 in England and Wales reported using a legal or illegal recreational drug within the previous year. In the United States, more than half of people aged 12 and older have used substances such as cannabis, cocaine, or opioids at least once. Despite their widespread use, the long-term effects of these drugs on stroke risk have remained uncertain.

Vast data sharpen risk

To examine the question more closely, researchers from the Department of Clinical Neurosciences at the University of Cambridge carried out a meta-analysis of studies involving more than 100 million people. A meta-analysis pools and analyzes cohort data from the published evidence. By combining studies that may be too small or inconsistent on their own, this method can produce stronger conclusions.

The findings, published in the International Journal of Stroke, showed that cocaine and amphetamine use were each linked to roughly double the risk of stroke (cocaine increased the risk by 96%, amphetamines by 122%). Cannabis use was associated with an increase of about 37%. The researchers did not find a statistically significant association between opioid use and stroke risk.

When the analysis was limited to people younger than 55, amphetamine use was associated with an almost threefold rise in stroke risk (an increase of 174%). Cannabis use also raised stroke risk, though by a smaller amount (14%), while cocaine use was linked to a 97% increase.

Genetics points beyond correlation

To investigate whether these relationships might be causal, the researchers also used a statistical method called Mendelian randomization. This approach examines naturally occurring genetic variants related to risk factors and stroke to assess whether evidence supports a causal association with a specific risk factor.

Problematic alcohol use was associated with a higher risk of cardioembolic stroke and large artery stroke, while alcohol addiction increased the overall risk of stroke.

The researchers could not apply Mendelian randomization to amphetamine use because large genetic datasets containing information on amphetamine use are not currently available.

Stroke pathways offer clues

The researchers suggest several possible mechanisms that may explain why these drugs are associated with higher stroke risk. These include sudden blood pressure spikes, blood vessel spasm and narrowing, heart rhythm problems, increased blood clotting (especially cannabis), and inflammation or vasculitis (especially amphetamines). All of these are established pathways that can contribute to ischemic strokes, which are caused by blood clots, and hemorrhagic strokes.

Dr. Megan Ritson from the Stroke Research Group at the University of Cambridge said, "This is the most comprehensive analysis ever conducted on recreational drug use and stroke risk and provides compelling evidence that drugs like cocaine, amphetamines, and cannabis are causal risk factors for stroke. These findings give us stronger evidence to guide future research and public health strategies."

Dr. Eric Harshfield, Alzheimer's Society Research Fellow at the Department of Clinical Neurosciences, said: "Our analysis suggests that it is these drugs themselves that increase the risk of stroke, not just other lifestyle factors among users. Taken together, our findings emphasize the importance of public health measures to reduce substance abuse as a way of helping also reduce stroke risk."

DOI: 10.1177/17474930261418926

The research was funded by the British Heart Foundation, with additional support from the National Institute for Health and Care Research Cambridge Biomedical Research Center.