AMID varying study results regarding the benefits of its use, some health experts are now saying that outside of what is medically prescribed, including recreational purposes, cannabis or marijuana is associated with a higher overall risk of stroke, with evidence pointing to chronic, long-term exposure rather than casual consumption as the primary driver of this cardiovascular danger.
Based on a landmark global study conducted at the University of Cambridge, researchers found that there is a 37-percent risk of strokes in most cannabis users.
The comprehensive study, entitled ‘Does illicit drug use increase stroke risk? A systematic review, meta-analyses, and Mendelian randomization analysis’, was published in the International Journal of Stroke by a research team that included scientists from the Cambridge Department of Clinical Neurosciences.
Dr. Megan Ritson, post-doctoral research associate from the Cambridge Stroke Research Group and lead author of the study, provided crucial context regarding how their findings apply to different usage patterns, substance types and global populations.
Ritson was joined chronic disease and genetic epidemiologist Dr. Eric Harshfield and honorary consultant neurologist Prof. Hugh Markus.
Citing the 37-percent risk increase for cannabis, the Cambridge researcher noted that a sensitivity analysis focusing strictly on recent or occasional exposure caused the statistical link to lose significance.
“This may suggest the risk reflects longer-term use rather than occasional exposure,” she enthused, though adding that current data limitations prevent a definitive conclusion.
The Cambridge team conducted a systematic review and meta-analysis of 32 international studies comprising more than 100 million total participants across hospital-based, population-based and administrative registries.
The research evaluated the cerebrovascular impacts of several substances used outside of regulated medical contexts, finding that while stimulant drugs like amphetamines (122 percent increased risk) and cocaine (96 percent increased risk) roughly doubled overall stroke risk, cannabis consumption presented a distinct threat of its own.
In contrast, the meta-analysis found no statistically significant association between opioid use or nicotine dependence and stroke risk, underscoring that stroke danger is driven by specific vascular mechanisms unique to stimulants and cannabis.
The genetic validation revealed distinct mapping between specific substances and stroke subtypes. First, cannabis use disorders were specifically linked to large artery strokes, driven by the drug’s propensity to heighten blood clotting tendencies, induce vessel spasms, and trigger sudden blood pressure surges.
Interestingly, the research revealed that cocaine dependence was strongly linked to cardioembolic strokes—where a blood clot forms in the heart and travels to the brain—and intracerebral hemorrhages (bleeding within brain tissue). Overall genetically predicted substance use disorder carried an almost eightfold increased risk (OR = 7.79) for intracerebral hemorrhage.
In a separate sub-analysis focusing on individuals under the age of 55, cannabis use was associated with a 14-percent elevated stroke risk while amphetamine and cocaine usage showed risk spikes of 174 percent and 97 percent, respectively.
