Cannabis use increased risk for stroke in young adults

Patients exhibiting ischemic stroke and transient ischemic attack were 2.3 times more likely to have cannabis detected in urine tests than other age- and sex-matched patients, according to recent findings presented at the International Stroke Conference 2013.

“This is the first case-control study to show a possible link to the increased risk of stroke from cannabis,” P. Alan Barber, PhD, MD, professor of clinical neurology at the University of Auckland in New Zealand, said in a press release. “Cannabis has been thought by the public to be a relatively safe, although illegal, substance. This study shows this might not be the case; it may lead to stroke.”

Although a temporal relationship has been reported in previous studies — ischemic stroke and transient ischemic attacks (TIA) developing within hours of cannabis use — the association had not been confirmed.

Barber and colleagues performed a case-control study of urine screens for cannabis among 160 patients aged 18 to 55 years with consecutive ischemic stroke (n=150) or TIA (n=10). The researchers then matched hospital patients against a control cohort of age, sex and ethnicity who were screened for cannabis using anonymized urine samples obtained for other indications.

According to study results, 25 (15.6%) of ischemic stroke/TIA patients exhibited positive cannabis drug screens — these patients were more likely to be male and tobacco smokers.

In comparison, only 13 (8.1%) of the control cohort tested positive for cannabis in urine samples. The researchers observed no differences in age, vascular risk factors or stroke mechanism between cannabis and nonusers.

“This study provides the strongest evidence to date of an association between cannabis and stroke, with ischemic stroke and TIA patients twice as likely to have recently used cannabis as control participants,” Barber and colleagues wrote. “Cannabis is generally perceived as having few serious adverse effects. This study suggests that this may not be the case and that the association between cannabis and stroke warrants further investigation.”

According to the researchers, this study offers the most convincing evidence to date of an association between cannabis and stroke. However, this association is complicated because all but one of the stroke patients who were cannabis users also were habitual tobacco users.

“We believe it is the cannabis and not tobacco,” Barber said in the press release. “[Further studies] may prove difficult given the risks of bias and ethical strictures of studying the use of an illegal substance. However, the high prevalence of cannabis use in this cohort of younger stroke patients makes this research imperative.”

For more information:

Barber PA. Abstract #147. Presented at: International Stroke Conference 2013; Feb. 5-8, 2013; Honolulu.

Disclosure: The researchers reported no relevant financial disclosures.