HealthDay News — Middle age stroke patients were 2.3 times more likely to smoke cannabis than healthy middle-aged controls, results of a New Zealand study reveal. 

“Cannabis has been thought by the public to be a relatively safe, although illegal substance,” study researcher Peter A. Barber, PhD, MD, a professor of clinical neurology at the University of Auckland, said in a press release. “This study shows this might not be the case. It may lead to stroke.”

Barber presented the results today at the the American Stroke Association’s International Stroke Conference in Honolulu.

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After encountering a 30-something stroke patient with none of the typical risk factors, such as diabetes or hypertension, but who smoked marijuana, Barber and colleagues searched the literature and found similar temporal associations in case reports.

To better understand the relationship between pot smoking and stroke, Barber and colleagues conducted urine screens for cannabis on 160 consecutive patients aged 18 to 55 years (100 of them men) with ischemic stroke (94%) or transient ischemic attack (TIA, 6%) and age-, sex- and ethnicity-matched controls who had urine samples obtained for various reasons.

They found that 15.6% of stroke patients tested positive for cannabis compared with 8% of controls. Marijuana use was the only factor associated with increased risk of ischemic stroke or TIA (OR=2.30; 95% CI: 1.07-4.95) in a logistic regression analysis adjusted for age, sex and ethnicity.

“This is the first case-controlled study to show a possible link to the increased risk of stroke from cannabis,” Barber said.

One major limitation of the study is that researchers were not able to adjust for tobacco smoking, because all stroke patients who smoked cannabis were also regular tobacco users, and there was no data available on tobacco use among study controls.

The next step is to conduct another study to determine whether there’s an association between cannabis and stroke independent of tobacco use.

“This may prove difficult given the risks of bias and ethical strictures of studying the use of an illegal substance,” Barber said. “However, the high prevalence of cannabis use in this cohort of younger stroke patients makes this research imperative.”


  1. Barber PA et al. Abstract #147. “Cannabis, ischemic stroke and transient ischemic attack: A Case Control Study.” International Stroke Conference 2013; Honolulu, Hawaii: Feb. 6-8, 2013.