Using data from the Nationwide Inpatient Sample (NIS), a database of information from more than 1,000 hospitals around the country, researchers compiled records from patients 18 to 55 years of age who were discharged in 2009 and 2010. Hospitals in forty-four states and Washington, D.C., contributed data to the NIS database, according to lead researcher Dr. Aditi Kalla.
Of 20 million health records, marijuana use was found in 1.5 percent, or about 316,000 patients, Kalla says. Researchers then compared cardiovascular disease rates in these patients to rates in patients not reporting marijuana use.
"Like all other drugs, whether they're prescribed or not prescribed, we want to know the effects and side effects of this drug," Kalla says. "It's important for physicians to know these effects so we can better educate patients, such as those who are inquiring about the safety of cannabis or even asking for a prescription for cannabis."
Einstein Medical Center in Philadelphia, was able to utilize NIS for her research after the healthcare network paid for access to the database.
"We were not funded by anybody," Kalla says of the study. "Our hospital purchased this database. It's a publicly available database, and it's used for research."
After publishing her findings, however, Kalla says she received immense backlash from people saying her study must have been funded by the pharmaceutical industry, or even by the Trump administration.
"I didn't receive any phone call from Trump [asking me] to come up with fake news or anything like that," she says with a slight chuckle. "No pharmaceutical company has ever gotten in touch with me.
"This is definitely not an anti-cannabis study. I think we accepted that every medication has effects that we did not know occurred, whether that be good or bad, and we just wanted to understand that better," she explains. "We can easily prescribe, or educate our patients on using Tylenol or Ibuprofen. I mean, it's even written on the bottle.... We just want to be able to do the same thing for cannabis. We did not go into this trying to find negative results."
But as they looked at the data, the patient files they reviewed indicated that cannabis users are potentially more at risk for heart problems.
"I'm not necessarily saying cannabis use increases your risk of developing something," Kalla says. "In this population, they had a higher risk of having heart failure and stroke. I want to be careful; I don't want to say that we are concluding that cannabis use increases your risk of developing those symptoms."
Kalla and her team focused primarily on five conditions: heart failure; cerebral vascular accident, which usually results in a stroke; coronary artery disease; sudden cardiac death; and angel defibrillation.
Although the researchers found that cannabis users had a higher rate of heart failure, stroke, cardiac disease and sudden cardiac death, Kalla says it's important to note that the majority of the cannabis users were slightly older and there were more males in the group. Men are often at higher risk for cardiovascular diseases, so after getting these results, her team tried to isolate the problems specifically tied to cannabis.
After correcting for those risk factors, cannabis users were 26 percent more likely to suffer from a stroke and 10 percent were more likely to experience heart failure. Once researchers account for the additional risk factors, sudden cardiac death and coronary disease did not appear to be related to cannabis.
As with alcohol, the effects of cannabis use are reversible, Kalla notes.
"More than two drinks per day is considered severe alcohol consumption, and severe alcohol consumption has also been associated with a higher risk of heart failure, but we know that is a reversible form of heart failure," she explains. "So when patients stop drinking alcohol, many of them have return of normal heart function — very similar to what they saw in the case reports of cannabis users."
Kalla's team seems to have identified a trend, but as is so often the case with marijuana studies, more research has to be done before definite conclusions can be drawn. One thing that's making it easier? Kalla says she's seen more and more patients admitting to their cannabis use, even in states where the drug is not legal.
"I've noticed, even from when I started medical school to now, patients seem to shy away a little bit when you ask them just about social history and if they use any other drugs," she says. "Now, I've noticed, people are very willing to admit they use marijuana, which is great. As doctors, we want to be able to understand everything you're consuming so we can give the best advice."
Kalla did her training in Georgia and South Carolina, states with no legal marijuana, and she says that even in those states patients were forthcoming about their cannabis use.
"Cannabis is getting more accepted socially. I think it's now finally entering the medical realm, and I think we'll be able to do more research to give better answers to our patients and to the general public," Kalla says. "This is such an emerging area of research, and I'm so excited to be part of it."