Looking at Heart Risks in Young Pot Users

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Harvard Medical School
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Looking at Heart Risks in Young Pot Users

News Review From Harvard Medical School

April 24, 2014

News Review From Harvard Medical School -- Looking at Heart Risks in Young Pot Users

Marijuana use may increase heart problems in young adults, especially if they are already at risk, authors of a small study say. The study was based on reports to a drug-abuse surveillance program in France. Doctors are required to report drug-abuse cases linked with serious health problems. Researchers looked at data for 2006 through 2010. In those years, 35 reported cases involved heart or blood vessel problems among marijuana users. The average age was 34. Nine of the 35 died. Nearly half had high blood pressure, high cholesterol or some other factor that increased their risk of heart disease. During the study years, heart disease cases rose from 1.1% to 3.6% of all reported problems in marijuana users. The cases included 20 heart attacks or symptoms indicating a strong risk of immediate heart attack. Researchers said more study of marijuana risks is needed as use becomes legal in more places. But some experts said the study is not reliable. They noted that it relies on only the cases that were reported. The Journal of the American Heart Association published the study. HealthDay News wrote about it April 23.


By Robert H. Shmerling, M.D.
Harvard Medical School


What Is the Doctor's Reaction?

Last week, it finally happened: one of my arthritis patients asked me if I could prescribe marijuana for her pain. 

I was expecting this. Massachusetts legalized marijuana for medical use last year.  However, the state is still sorting out the details of how it will work. Once all of the rules are sorted out and the dispensaries are open, I will have to decide whether prescribing marijuana is a good idea for this patient and others.

There's little doubt that the legal landscape for marijuana has changed in recent years. Several states have legalized its medical or recreational use. Others have dropped criminal penalties for possession. And more states are considering similar measures.

Where medical use is already legal, marijuana should be viewed just like any other drug. Patients and doctors will need to assess:

  • Whether it's likely to be effective for a specific problem
  • Whether it is acceptably safe
  • Whether there are better options

There is some evidence that marijuana can be helpful for several conditions, including:

  • Glaucoma
  • Chronic pain from nerve disease, arthritis and other causes
  • Multiple sclerosis

And what about safety? In states where recreational use is legal -- Colorado and Washington for now -- legislators have already decided that marijuana is acceptably safe. But not everyone agrees. In fact, recent research raises some concerns. These include the possibility that marijuana use may harm:

  • Breathing
  • Reproductive function
  • The immune system
  • Brain health

A newly published study raises concerns about the effects of marijuana use on heart and blood vessel health. Researchers in France identified 35 cases of heart or blood vessel (cardiovascular) problems that were attributed to marijuana use. They were reported between 2006 and 2010. The study found that:

  • Most people with marijuana-related heart or blood vessel problems were young or middle aged. The average age was 34. About 86% were male.
  • These problems were relatively rare. They were only about 2% of all marijuana-related health problems reported to a national network that tracked drug abuse and dependence.
  • Twenty of the 35 cases involved heart attacks or symptoms of a potential heart attack. Ten others had circulation problems in the arms or legs. The rest involved brain circulation or an abnormal heart rate.
  • Nine of the 35 people died.

This news is clearly worrisome. But it's hard to know how common marijuana-related heart and blood vessel problems truly are. This study relied on "spontaneous reports" by doctors of drug-related problems among their patients. So these problems could be vastly underreported.

On the other hand, this sort of study tends to report the most dramatic and dire cases. At the time of this study, there were an estimated 1.2 million regular marijuana users in France. Some of them may have also been using cocaine, alcohol or tobacco, too. Or they may have had other factors that increased their risk of heart and blood vessel disease. So this study might be overstating the problem.

One thing seems certain: marijuana use may come with risks and benefits that we don't completely understand.


What Changes Can I Make Now?

If you believe that marijuana is harmless, it may be time to rethink your position. This is particularly true if you already have health problems that might get worse after using marijuana. Heart and blood vessel disease may be a good example, as this latest research suggests. At the very least, we need much more information about the risks of smoking or consuming cannabis.    

Until we have more information, I recommend the following for adults interested in smoking or consuming marijuana:

  • Review the risks of marijuana use with your doctor. Your particular health problems, medicine use and family history may make a difference.
  • If you want to use marijuana for a medical problem, review the evidence of its effectiveness and alternative treatments with your doctor.
  • Don't smoke it. Inhaling smoke of any kind is harmful to the lungs, and marijuana is no exception.
  • Use moderation. Avoid consuming marijuana in excess or so often that you can't think or function normally.

Teenagers, children and those who live where marijuana is illegal should not use it at all.


What Can I Expect Looking to the Future?

You can expect proponents of marijuana to emphasize the benefits of the drug. Opponents, of course, emphasize the risks. I hope that research will clarify just where the truth lies. We need more studies about dosing and whether the effects vary based on how you consume marijuana (smoking or some other method). Such research should lead to more rational laws and regulations.

By the time another patient asks me to prescribe marijuana, I hope to have better information that can guide my advice.

Last updated April 24, 2014

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