Marijuana use may lead to stroke and disability

July 29, 2016

By Michelle Strausbaugh

Manoj K. Mittal
Manoj K. Mittal

A recent Gallup poll found that 58 percent of Americans now support legalizing the recreational use of marijuana, and 35 states currently allow for some form of recreational or medical use of marijuana. One of the reasons a growing number of people are in favor of decriminalizing the use of marijuana is that many are under the impression that smoking pot is relatively harmless. A 2015 survey by the Pew Research Center found that 36 percent of those surveyed believed that marijuana is no more dangerous than other drugs such as alcohol or cigarettes.

But research by scientists at the University of Kansas Medical Center and the University of Missouri-Kansas City (UMKC) might alter that view. The new study indicates there could be a link between marijuana use and an increased chance of having a stroke.  

Manoj K. Mittal, M.D., an assistant professor in the Department of Neurology at KU Medical Center along with UMKC medical students Adithi Y. Reddy and Kavelin Rumalla, have done retrospective datamining research using a large national database (Nationwide Inpatient Sample), that shows that marijuana can significantly increase the chance of a person being hospitalized due to an acute ischemic stroke - a stroke that occurs when blood being supplied to the brain is cut off by a clot.  

Stroke is the fifth-leading cause of death in the United States, and acute ischemic stroke accounts for 87 percent of all strokes. Stroke also is the leading preventable cause of disability.  

"Since the commonly-held belief has been that marijuana was safe, it's very hard now to convince people it can be harmful to their health. We believe the reason marijuana was previously thought to be safe was not really because it was safe, but because there was not much evidence one way or another," Rumalla said. "  

Key findings   

Mittal's team used data collected by the federal Agency for Healthcare Research and Quality about nationwide hospital admissions and discharges. They used statistical software to isolate the information relevant to their study, controlling for confounding factors like use of tobacco, alcohol, cocaine and amphetamines. They spent hundreds of hours ferreting out answers from that subset, which consisted of two million marijuana users and 116 million non-users.  

Mittal and the students found that marijuana users, ages 15-54, were 17 percent more likely to have an acute ischemic stroke leading to hospitalization than non-users. The correlation was even more dramatic among 25-34-year-old users, who were 126 percent more likely to be hospitalized than non-users.   

The team's research, "Recreational marijuana use and acute ischemic stroke: A population-based analysis of hospitalized patients in the United States," was published in the May issue of the Journal of the Neurological Sciences. A counterpart study, "Association of Recreational Marijuana Use with Aneurysmal Subarachnoid Hemorrhage" was published in the February issue of the Journal of Stroke and Cerebrovascular Disease.  

"We're not making a political statement to condone or oppose the legalization of marijuana. We do this so the general public is well aware of the risks that accompany this misperceived drug," said Reddy.   

Inspired by a patient   

A stroke patient inspired Mittal's investigation into a possible link between marijuana use and stroke.  

"I had a young patient in his 20s with no risk factors for stroke.  His urine tested positive for marijuana. That made me wonder if it was a factor," he said.  

This finding triggered Mittal to search the scientific literature for any related case studies and to enlist Reddy and Rumalla. While there were scattered case reports of perceived association, there was no formal epidemiological research establishing an independent association between marijuana use and stroke.   

How it works   

Tetrahydrocannabinol (THC), the chemical responsible for most of marijuana's psychological effects, causes blood vessels in the brain to spasm, which can lead to both acute ischemic or hemorrhagic stroke. The stroke prevents the brain from getting the blood and oxygen it needs and may result in paralysis, impairment of vision, speech, language and/or memory.   

In addition to the increased stroke risk, the team's analysis showed that marijuana use was even more dangerous as a stroke risk factor when combined with other drugs.   

More study is needed, but cannabis' classification as a Schedule I drug by the Food and Drug Administration (FDA) prevents it from being used in research with patients. Unless and until the drug is re-classified, the science will be limited to epidemiological conclusions.   But with more and more states legalizing it, the drug's FDA status may change, Mittal said. Meanwhile, publication of this study may lead researchers in other specialties and in other countries to investigate the ill effects of marijuana.  

"Our hope is that the current data would stimulate further research to verify our findings as well as begin getting the word out on marijuana's potential link to stroke," Rumalla said. 

Last modified: Oct 20, 2016
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