A heart surgeon has warned that smoking cannabis carries significant cardiovascular and respiratory risks, pushing back against the widespread belief that marijuana is harmless because it is “natural” or legal in many parts of the United States. His comments come as medical professionals draw renewed attention to conditions linked to heavy cannabis use, including cannabis hyperemesis syndrome, a disorder marked by cycles of intense abdominal pain and severe vomiting.
Cannabis hyperemesis syndrome, now recognised in the World Health Organization’s International Classification of Diseases, has been documented in long-term users who experience prolonged bouts of nausea and vomiting that can last for up to two days. Some patients report retching dozens of times per day. Although its exact cause remains unclear, one leading theory is that extended overstimulation of receptors in the body’s endocannabinoid system may trigger the condition.
But while CHS affects only a proportion of heavy cannabis users, cardiovascular specialists say the broader health risks of smoking marijuana remain underappreciated. Dr Jeremy London, a heart surgeon who shares medical advice on social media, said inhaling any form of smoke places stress on the lungs and the circulatory system, regardless of whether the substance is derived from tobacco or cannabis. He noted that the lungs are designed for air exchange only, and the introduction of burnt particulate matter — from any source — can harm tissue over time.
London said he frequently encounters patients who assume cannabis is safe because it is plant-based or prescribed in some medical contexts. However, he pointed to research showing an elevated risk of coronary artery disease and acute heart attack among people who smoke marijuana regularly. According to him, the increased risk ranges from roughly 1.3 to two times that of non-users, similar to the elevated cardiovascular risk associated with high blood pressure or high cholesterol.
He also described what he sees during surgery in patients with long-term cannabis-smoking habits. In his experience, the lungs of heavy marijuana smokers can appear darkened and damaged in ways comparable to individuals exposed to coal dust, despite some of those patients never having smoked cigarettes. He said several required bypass surgery due to severe arterial blockages.
Other experts have echoed those concerns. A recent study examining the relationship between cannabis use and heart attack risk found a significantly higher likelihood of cardiac events among users, estimating the increase at roughly 50 percent compared with non-users. Meanwhile, the American Lung Association has warned that smoking cannabis can injure lung tissue, inflame airways and impair normal respiratory function. The organisation distinguishes between cannabis consumption methods, noting that smoke — whether from tobacco or marijuana — contains toxins and carcinogens.
Health professionals say that as marijuana becomes more widely available, misconceptions about its safety have grown. They emphasise that while cannabis may have therapeutic uses for some patients, smoking it carries clear risks. Clinicians are calling for more public awareness, better research and greater caution among users who may underestimate the drug’s impact on the heart and lungs.
