American scientists have found that among patients with heart failure (the heart muscle can not pump enough blood to meet normal body demands), those who used marijuana were less likely to make a complication called atrial fibrillation, or " A-fib ", a type of irregular heartbeat that can aggravate symptoms.
Also, patients with heart failure who used marijuana were less likely to die in hospital, unlike those who did not use the drug, the study found.
However, researchers point out that it currently does not recommend that patients with heart failure use marijuana.
This finding was unexpected, as scientists have so far hypothesized that marijuana use would be linked to an increase in health complications for patients with heart failure.
"I was very surprised to find that there was little association," said study author Dr. Oluwole Adegbala, resident at Englewood Hospital and New Jersey Medical Center. Adegbala presented these results at a reunion of the American Heart Association, which took place November 11-15, in Anaheim, California.
But researchers say it's too early to recommend marijuana for heart failure patients. Because the study is the first to find a link between the use of marijuana and a low probability of A-fib among heart failure patients, more studies are needed to confirm the results, Adebbala.
A-fib may be both a cause and a consequence of heart failure, and the two conditions often appear together, according to a review in 2015. Patients with heart failure and A-fib have a pessimistic prognosis and an increased risk of early death unlike those who have only one of the two conditions.
Several small studies (including individual case studies) found a link between marijuana use and A-fib development. Adegbala and colleagues decided to explore this link more closely by examining a vast database of patients hospitalized in the United States. They analyzed information about more than 6 million patients with heart failure during 2007-2014. Of these, about 1,200 consumed marijuana and were drug addicts, and about 23,000 used marijuana but were not addicted to it.
They found that non-addicted marijuana users had 18% lower probabilities (31% for addicted users) to develop A-fib compared to patients who did not use marijuana.
In addition, for non-addicted marijuana users, there is a 46% lower probability (58% for addicted users) of dying in the hospital compared to those who did not use marijuana.
The findings were maintained even after the authors of the study considered factors that could affect outcomes such as people's age, socio-economic status, and the use of other drugs. Previous studies may link marijuana to an increased risk of A-fib because these studies could not take into account the use of other substances, such as alcohol, that could increase the risk of A- fib, Adegbala explained.
It is unclear how it could reduce marijuana risk of A-fib and mortality among patients with heart failure, the specialist said. Studies in animals suggest that activation of cannabinoid receptors (which are found throughout the body and are activated by marijuana compounds) can reduce high blood pressure and atherosclerosis, both of which are risk factors for A-fib. In addition, as found in studies, cannabidiol, a compound of marijuana, can reduce inflammation in the body, which is also a risk factor for A-fib, he said.
However, more research is needed to explore how marijuana can reduce the risk of A-fib in patients with heart failure and more precisely what marijuana components are responsible for this effect, Adegbala said.
Marijuana is the most commonly used psychoactive substance in the world under international control. In 2013, approximately 181.8 million people aged 15-64 used this substance for non-medical purposes worldwide, according to a UNODC report of 2015. According to the World Health Organization, there is a growing demand for treatment for cannabis use disorders and associated health conditions. Over the last quarter century, significant research has been carried out into the health effects of cannabis use, but these are often limited and rarely have a clear causal link. So the science around the world's most misunderstood plant, from which marijuana is extracted, has not been exhausted, and the discovery of its beneficial or health-conscious properties still constitutes a challenge for the scientific community.