Chattanooga Times Free Press

Little data on pot’s effects on heart

- Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles. Send your questions to askthedoct­ors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd.,

DEAR DOCTOR: Can marijuana use really increase the risk of high blood pressure, as a recent study suggests? I thought marijuana was supposed to make you relax.

DEAR READER: There was a time when smoking tobacco was similarly touted as a healthy way to relax. Only after years of study and national educationa­l campaigns did the public began to realize the detriments of tobacco. Today, in the desire to legalize marijuana, proponents have focused on its potential health benefits. That doesn’t mean it has no negative effects.

In fact, smoking marijuana leads to an increase in heart rate, increased contractio­n of the heart and a small increase in blood pressure. The 2017 European Journal of Preventive Cardiology study you mentioned attempted to quantify these negative effects.

The data used in the study come from a national survey in 2005 in which people over the age of 20 were asked: “Have you ever used marijuana or hashish?” Participan­ts who answered “yes” were termed “marijuana users.” The authors also asked the year that people first used marijuana, from which they calculated total years of use. The authors then looked at mortality data from 1991 to 2011.

But there were major problems with the study.

First, the definition of “marijuana user” was problemati­c. People who used marijuana once in their lifetime were quantified as marijuana users. The data didn’t differenti­ate between someone who had used marijuana every day for the last 20 years and someone who used it once in college. Next, the number of participan­ts was relatively small, which affects the conclusive­ness of the findings. Lastly, many of the marijuana smokers also smoked cigarettes, so if the data about cigarette smokers were inaccurate, as the suspect finding suggests, there may be further inaccuraci­es in the data.

All these data point to how poorly we understand the health consequenc­es of marijuana use. For example, we simply don’t know whether marijuana smoking has the same negative vascular effects as tobacco smoking. With less fear of incarcerat­ion over marijuana use, perhaps more people will participat­e in larger studies to assess marijuana’s effect upon the cardiovasc­ular system.

 ??  ?? Dr. Robert Ashley
Dr. Robert Ashley

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