Dr. Roach: Evidence linking edible cannabis and blood clots is slim

Keith Roach
To Your Health

Dear Dr. Roach: I am a 64-year-old male who considers himself active and healthy. In July 2020 I had a stroke, treated in a timely manner with a tissue plasminogen activator, and I have no residual effects. I will, about two to three times a month, take an edible cannabis to help me sleep or deal with a Crohn’s episode. My primary care provider does not like me taking any edible cannabis, as he says it is proven to lead to strokes and blood clots. What are your thoughts?

— B.G.

Dr. Keith Roach

Dear B.G.: The data linking cannabis to blood clots and strokes is mixed. There is evidence that smoked cannabis activates platelets, which is likely to increase clot risk. However, some studies of cannabis users showed increased clot and stroke risk only among those who smoked tobacco as well. I could not find any strong (or even marginal) data linking edible cannabis to an increased risk of stroke or blood clots. At the dose you are taking, I think it is very unlikely to do so.

Since many people like you are using cannabis as a medication, it is very important to recognize the possible adverse effects, just as we do with all other medications. Many more high-quality studies are needed before we can have a better idea of what the potential harms may be of cannabis. In your case, I think the potential for harm is low.

Dear Dr. Roach: Is COVID-19 infection a cause of heart block? I recently had a complete heart block, tested positive in the ER for COVID-19 (symptomless and post-vaccine), and was fitted with a permanent pacemaker later the same day. I’m 63, female, in good health except for a luckily nonsevere, 10-year diagnosis of Sjogren’s syndrome.

My cardiologist doesn’t think the heart block is due to COVID-19, but I’ve seen articles in Medline that report cases of heart block during COVID-19 infection. Is it too early in the disease’s research to know if it’s a direct cause?

— B.J.S.

Dear B.J.S.: Heart block is a condition where the electrical impulse from the top chambers of the heart to the bottom are completely blocked. I found case reports and a case series of people developing heart block while in the hospital with COVID-19 infection. In the case series, all three patients were severely ill — rhythm problems can happen in people with critical illness from any cause — and all cases of heart block recovered without need for pacemaker. In a larger series of 700 COVID-19 patients monitored for rhythm problems, none developed heart block.

So while it is plausible the COVID-19 infection may have caused your heart block, this complication seems to be uncommon, and it may also be just that it happened to occur (or at least was noticed) at the same time you had an asymptomatic case of COVID-19.

There are case reports of heart block developing in people with Sjogren’s syndrome, an autoimmune disease that particularly affects the cells that produce saliva and tears. It’s possible that it was the Sjogren’s, not the COVID-19, that caused the permanent heart block.

Readers may email questions to ToYourGoodHealth@med.cornell.edu.