A Cambridge-led meta-analysis of more than 100 million people has found that cannabis use is associated with a 37% higher risk of stroke, with cocaine and amphetamines carrying even steeper increases of 96% and 122% respectively. The findings, published in the International Journal of Stroke, hold even among adults under 55, a group that saw the risk nearly triple with recreational drug use.
Researchers compiled data across dozens of prior studies to reach the 100-million-person sample size, a scale that lets them detect risk increases too small to show up reliably in any single smaller study. The elevated stroke risk applied broadly across cannabis, cocaine, and amphetamine use rather than being isolated to one substance.
Why Younger Adults Are Especially at Risk
Stroke has traditionally been framed as an older adult’s disease, but the near-tripling of risk among recreational drug users under 55 found in this analysis complicates that picture. Younger cardiovascular systems aren’t necessarily more resistant to the blood vessel and clotting effects that cocaine, amphetamines, and cannabis can produce, and a stroke at a younger age tends to carry a longer remaining lifespan of disability if a person survives one.
What This Changes
Cannabis has increasingly been treated as a comparatively low-risk substance as legalization has spread across more states, and this study adds a specific, quantified cardiovascular risk to that conversation rather than the more general warnings that have circulated previously. It doesn’t establish that cannabis causes stroke through a specific mechanism on its own, meta-analyses of this kind show association, not proof of direct causation, but a 37% risk increase across a 100-million-person sample is a large enough signal that it’s likely to factor into future public health guidance around cannabis use.
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