Young Frequent Cannabis Users Face Increased Stroke Risk, Says New Study
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Young people who use cannabis frequently may be more than twice as likely to have a stroke compared to non-users, according to the authors of a new preliminary study presented at the American Heart Association’s Scientific Sessions 2019.
The authors found that frequent cannabis users who also use cigarettes or e-cigarettes are at a 0.4 percent higher risk of experiencing a stroke compared to non-users – nearly a threefold increase of relative risk.
People who didn’t use tobacco products, but who reported using cannabis more than ten days a month, were nearly two-and-a-half times more likely to have a stroke compared to non-users.
Understanding cannabis and stroke risk
The study examined data from over 43,000 adults aged between 18 and 44, of whom 13.6 percent reported having used cannabis in the past 30 days. All of the data came from the 2016-17 Behavioral Risk Factor Surveillance System, a nationally representative cross-sectional survey carried out by the US Centers for Disease Control and Prevention.
On average, the researchers noted that the self-reporting cannabis users were more likely to be heavy drinkers and current cigarette/e-cigarette users, which the researchers acknowledge could have influenced their stroke risk despite attempts to adjust for these factors during analysis. Cannabis users were also often younger, non-hispanic white or black, were less likely to be college graduates, and were more physically active than those reporting no cannabis use.
While these increased risk statistics look highly concerning, it’s important to acknowledge that these numbers released by the researchers are a measure of relative risk, not absolute risk.
Relative risk is used to compare the risk between two different groups. In this case, the relative risk was of having a stroke for cannabis users, compared to non-cannabis users. Absolute risk is a measurement of the actual risk of developing the disease in question over a time period.
As the twitter account @justsayrisks (run by epidemiologist and science writer Gideon M-K) points out, the absolute stroke risk increase for cannabis users is still very low – somewhere around 0.4 percent.
The researchers highlight that the study was observational of the data, and so identified a potential link, rather than proving a biological cause and effect. Previous studies have identified a link between cannabis use and increased numbers of blood clots, which could in turn increase the risk of stroke. Other theories include that cannabis may lead to a temporary narrowing of blood vessels in the brain.
“Young cannabis users, especially those who use tobacco and have other risk factors for strokes, such as high blood pressure, should understand that they may be raising their risk of having a stroke at a young age,” said lead study author Tarang Parekh, a health policy researcher at George Mason University in Fairfax, Virginia, in a statement. “Physicians should ask patients if they use cannabis and counsel them about its potential stroke risk as part of regular doctor visits.”
More cannabis research from the Scientific Sessions
Also featuring at the AHA Scientific Sessions, was a poster presentation from researchers in Oklahoma who have discovered a possible link between cannabis use disorder and serious heart rhythm abnormalities, known as “arrhythmia.”
People with cannabis use disorder (CUD) – the medical diagnosis given for problematic cannabis use – were seen to have a 50 percent greater risk of being hospitalized for arrhythmia compared to non-users. Some arrhythmias are benign and cause no long-term harm, but the condition can be life-threatening.
Using data from the Agency for Healthcare Research and Quality’s Nationwide Inpatient Sample, the researchers found that young African American men with CUD had the greatest risk of being hospitalized for arrhythmia, despite CUD being most common among white men, aged 45 to 54.
“The effects of using cannabis are seen within 15 minutes and last for around three hours. At lower doses, it is linked to a rapid heartbeat. At higher doses, it is linked to a too-slow heartbeat,” said Rikinkumar S. Patel, a resident physician in the department of psychiatry at the Griffin Memorial Hospital in Norman, Oklahoma, in a statement.
“The risk of cannabis use linked to arrhythmia in young people is a major concern, and physicians should ask patients hospitalized with arrhythmias about their use of cannabis and other substances because they could be triggering their arrhythmias,” said Patel.
“As medical and recreational cannabis is legalized in many states, it is important to know the difference between therapeutic cannabis dosing for medical purposes and the consequences of cannabis abuse. We urgently need additional research to understand these issues.”