09 May Does Marijuana Increase Stroke Risk in Young Adults?
MedicalResearch.com Interview with:
Tara Dutta M.D.
Vascular Neurology Fellow
University of Maryland Medical Center
MedicalResearch: What are the main findings of the study?
Dr. Dutta: We analyzed data from the Stroke Prevention in Young Adults Study in order to evaluate for an association between self-reported marijuana use and ischemic stroke. 1,101 cases and 1,154 age, gender, and race-matched controls, aged 15-49 years old, were recruited from the greater Baltimore-Washington area between 1992 and 2008. Interviews were conducted to assess for various potential stroke risk factors, including illicit drug, alcohol, and tobacco use. Individuals reporting use of vasoactive illicit drugs, including cocaine and amphetamines, were excluded, yielding 751 cases and 813 controls. Logistic regression analysis was used to determine the association between marijuana use and ischemic stroke, adjusting for age, gender, race, current tobacco use, current alcohol use, hypertension, and diabetes.
We did not find a positive association between marijuana use and ischemic stroke risk in our population of young-onset stroke patients compared to matched controls, even after controlling for current tobacco and alcohol use, hypertension, and diabetes. A statistically significant inverse relationship was observed between remote use (defined as any use over one year ago) and stroke risk (adjusted OR 0.77, CI 0.61-0.98, p = 0.03). We also looked to see whether recent use (in the past 30 days), and particularly recent heavy use, was associated with ischemic stroke risk as has been suggested in the medical literature. Though our data did not show this association, the number of patients reporting recent use in our study was very small.
MedicalResearch: Were any of the findings unexpected?
Dr. Dutta: Our hypothesis that marijuana use is associated with ischemic stroke was not supported by our data. Also, the inverse relationship seen between remote use and stroke risk was not expected.
MedicalResearch: What should clinicians and patients take away from your report?
Dr. Dutta: Although there is a growing body of medical literature describing a possible link between marijuana and ischemic stroke, we still do not have enough epidemiologic data to support an overall association. However, there may be a subgroup of individuals who are more prone to ischemic stroke in the setting of marijuana use. In several case series1,2 and review3, the majority of stroke cases attributed to marijuana use occurred in young males who reported heavy and often chronic marijuana use. Most had few traditional stroke risk factors. There was a tendency towards strokes affecting the posterior circulation, and a distinct imaging pattern seen of multifocal intracranial stenosis. Additionally, a high prevalence of marijuana use has been reported in a large series of patients experiencing reversible cerebral vasoconstriction syndrome4, raising the possibility that the drug may impact cerebral autoregulation. Numerous cardiovascular complications have also been reported in the setting of marijuana use (see recent reviews by Thomas, Kloner, and Rezkalla5,6), which may be another mechanism by which the drug could theoretically increase stroke risk in certain individuals. One of the challenges faced in studying the relationship between stroke and marijuana use is the fact that marijuana users often report concomitant use of tobacco and/or additional ilicit substances which may also increase stroke risk. A previous case-control study by Barber et al. showed a positive association between marijuana use and ischemic stroke risk prior to adjusting for tobacco, but nearly all stroke cases reported concomitant tobacco use7. It is also difficult to isolate the effects of cannabis itself given that marijuana may be mixed with tobacco, other street drugs, or chemical additives.
Additionally, although our data did show an inverse relationship between remote marijuana use and ischemic stroke risk, this does not necessarily infer a protective effect. One limitation of the study in this regard is that we do not have information about how frequently or heavily individuals used remotely, which could impact stroke risk. There also may be uncovered biases that could have contributed to this finding. For example, there may be something about this group of individuals that lowered their stroke risk independent of marijuana use. Perhaps they stopped using marijuana in addition to other behavior modifications, such as improved diet, exercise, or tobacco cessation in an effort to become more health conscious. Marijuana use has been previously associated with presence of hypertension, dyslipidemia, and higher caloric intake7 so use of the drug may be a marker of a lifestyle characterized by increased risk for cardiovascular disease. However, it is overall reassuring to remote users that this particular group did not appear to be at increased risk for stroke.
With use of both recreational and medical marijuana on the rise, patients are increasingly inquiring about the safety of use and health care providers are being faced with tough decisions about how to best guide patients. Certainly patients with known stroke or cardiovascular risk factors should cautioned about potential vascular side effects, and decisions about use of medical marijuana for treatment of a chronic condition should be based on evaluation of the benefit/risk ratio for each individual patient.
MedicalResearch: What recommendations do you have for future research as a result of this study?
Dr. Dutta: Future studies are needed to clarify the relationship between chronicity and burden of marijuana use and ischemic stroke, both remotely and in the time period immediately preceding stroke. This is particularly important from a public health standpoint. We know that use is on the rise in teens and young adults, and with legalization (of both medical and recreational marijuana) there will be increasing numbers of individuals using regularly. Fortunately it may be easier to study the effects of the drug moving forward, as those using regulated marijuana under medical supervision will be easier to identify and follow (without fear of legal repercussion), and hopefully it will be easier to exclude confounding effects of other substances such as tobacco and illicit drugs. Also, in cases of stroke that occur in the setting of marijuana use, attention to cerebrovascular imaging patterns may help to determine whether marijuana induces changes in cerebral autoregulation that predispose to stroke.
1. Wolff et al. Stroke 2011;42:1778-1780
2. Singh et al. J Stroke Cerebrovasc Dis. 2012;21:555-560.
3. Desbois and Cacoub. Ann Vasc Surg. 2013;Oct;27(7):996-1005
4. Ducros et al. Brain 2007;130:3091-101.
5. Rezkalla et al. J Am Heart Assoc. 2014;3:e000904
6. Thomas et al. Am J Cardiol 2014;113:187-190
7. Barber et al. Stroke 2013;44:2327-2329
8. Rodondi et al. Am J Cardiol 2006;98:478-484.
Marijuana Use and the Risk of Ischemic Stroke: The Stroke Prevention in
Young Adults Study
Abstract Presented at the American Academy of Neurology May 2014
Tara Dutta2, Kathleen Ryan2Yuching Cheng2, Steven Kittner1 and John Cole2
Neurology April 8, 2014 vol. 82 no. 10 Supplement S55.003