When we compare smoking marijuana to the other “drugs of abuse” we usually give pot a big thumbs up, and paint it in a positive light. And for good reason, marijuana is incredibly safe. Pot’s worst side effects don’t seem worse than tripping over one’s shoelaces, unless you prefer hiking in a Cambodian mine field.

Understandably then, we all tend to gloss over the occasional “chicken littles” of scientific observation when they become known. Such as the much-ballyhooed increase in heart attack risk within one hour of smoking weed. I dispatched that threat quite readily in a previous article. It reminded me of the hit piece, back when people were wearing bell-bottoms, when some malcontent claimed that LSD caused chromosomal damage to users. The article was debunked a week later but there was never a correction issued in the newspaper.

However, substantial evidence is accumulating that smoking marijuana may indeed have a short list of adverse effects that we all need to be aware of, especially young kids experimenting for the first time.

Marijuana’s cardiovascular effects are not associated with serious health problems for most young, healthy users, although occasional myocardial infarction, stroke, and other adverse cardiovascular events are reported. Marijuana smoking by people with cardiovascular disease poses health risks because of the consequences of the resulting increased cardiac work, increased catecholamine levels, carboxyhemoglobin, and postural hypotension[ref]J Clin Pharmacol. 2002 Nov;42(11 Suppl):58S-63S[/ref].


The last sentence restates the obvious talking points on marijuana side effects: pot increases blood pressure (only when lying down) while it stimulates the “fight or flight” response-causing tachycardia, a small increase in heart rate. A trivial amount of the oxygen-carrying molecule hemoglobin binds to the by-product of combustion, carbon monoxide (CO), to form carboxyhemoglobin. Carbon monoxide, a poisonous gas formed from combustion of carbon containing materials, is the same substance fashioned from burning charcoal on a grill which is one reason why you cannot light up your Weber Grill in the living room, the other reason is obvious I hope, as any personnel from the LA County-USC burn unit will testify-myself included.

CO is formed from smoking cigarettes or pot too. It can, in larger quantities, impede oxygen transport by competing for oxygen binding sites on hemoglobin. Is it clinically significant? I think not unless you already have underlying cardiovascular or lung disease such as COPD.

Lastly, the postural effects of pot are dizziness when you stand up too quickly. It’s called orthostatic hypotension. Be careful here as people have fainted from this. You can help prevent orthostasis by staying well hydrated, no gin is not a hydration medium, drink water and fluids that behave like water! A little trick I learned as an avid trekker is to put a big pinch of salt in each quart of fluid. This helps keep water in your vessels where it’s needed. Now let’s discuss a more serious problem.


In particular for kids, err, young adults experimenting with pot, honesty is the best policy so let’s begin with a frank discussion on the cardiovascular system as it pertains in particular to heart arrhythmias (palpitations). In a separate piece I’ll review stroke risk.

A study was completed recently that tried to address the incidence (the number of NEW cases in a given population) of a certain dangerous rhythm disturbance called atrial fibrillation from the use of pot.

Atrial fibrillation (AF) is actually a very common disorder among those with known heart disease, heart failure, or hypertension among other conditions. It is characterized as a fast heart rate, very fast sometimes, with rates well into the high 150s or higher. It is not benign. It can lead to stroke and numerous other serious complications, including cognitive decline.

The question I always ask patients is this: “does your heart sometimes feel like a trip hammer or does it feel like a bird is fluttering in your chest?” Occasionally, severe chest pain may accompany it in those with heart disease.

In the next segment we’ll discuss what a team of researchers discovered regarding AF and its relation to marijuana consumption.