Modifiable risk factor modification is obviously an important component of stroke prevention. Although marijuana use has been linked to adverse cardiovascular effects and vascular conditions such as reversible cerebral vasoconstriction syndrome, its effect on stroke risk is unclear. Barber et al. looked at patients who received urine drug screens and compared them to controls who were matched for age, sex, and ethnicity. Of the patients who were positive for cannabis, they found a higher proportion of men and smokers. Using a logistic regression model adjusting for age, sex, and ethnicity, there was an association between cannabis use and increased risk of ischemic stroke or TIA; however, this association was weakened when adjusting for tobacco use. A major limitation of the paper was in its selection of the control group, as socioeconomic status and use of other substances could not be adequately matched. As a result, it remains unclear whether the association between marijuana and stroke/TIA is confounded by these other factors. Nevertheless, it suggests that marijuana use is not benign. As many states are at a crossroads in the consideration for marijuana to be legalized for medicinal purposes, it is important to consider the growing evidence that cannabis may have more harmful effects than previously thought.