🧠 Giant study links cannabis, cocaine, amphetamines to strokes

A vast study involving more than 100 million people reveals a worrying link between the consumption of certain recreational drugs and the risk of stroke, particularly among young adults. While classic risk factors such as high blood pressure or smoking are well known, this research conducted by the University of Cambridge shows that cocaine, amphetamines, and cannabis could directly damage the brain's blood vessels.

To obtain these results, the researchers conducted a meta-analysis combining data from numerous previous studies, a statistical method that consolidates evidence by pooling samples of modest size. Published in the International Journal of Stroke, this synthesis examined the links between substance use and the occurrence of stroke, also including a genetic approach to test causality.


The results show that cocaine and amphetamines nearly double the risk of stroke (+96% and +122% respectively), while cannabis increases it by 37%. In people under 55, the effect is even more pronounced: amphetamines triple the risk (+174%). In contrast, opioids did not show a statistically significant association with stroke.

To distinguish a simple correlation from a cause-and-effect relationship, the team used a method called Mendelian randomization. This exploits genetic variants linked to drug use to check whether they influence stroke risk. The results indicate that cocaine use disorders are particularly associated with cerebral hemorrhages and cardioembolic strokes, while cannabis is linked to strokes due to large artery occlusion. This genetic analysis strengthens the hypothesis of a causal link.

Several mechanisms could explain this effect: cocaine and amphetamines cause sudden spikes in blood pressure, vessel spasms, and heart rhythm disorders. Cannabis, for its part, promotes blood clot formation. All these disturbances can lead to ischemic stroke (due to obstruction) or hemorrhagic stroke. The researchers emphasize that these drugs act directly, independently of other lifestyle factors.

These findings call for strengthening public health measures to reduce substance use. According to the authors, better prevention of drug addiction could also reduce the burden of stroke, especially in young adults where incidence is rising.