While cigarette smoking is the top risk factor for lung cancer, some scientific evidence suggests there is no link between marijuana smoking and lung cancer. That's according to a 2017 federal report that rounded up nearly two decades of studies on marijuana, research that's been limited by the federal government's classification of marijuana as a controlled substance.
While cigarette smoking is a major cause of heart disease, the report concluded it's unclear whether marijuana use is associated with heart attacks or strokes. But there's strong evidence linking long-term cannabis smoking to worse coughs and more frequent bouts of chronic bronchitis, according to the report from the National Academies of Sciences, Engineering and Medicine. The report also looked at other effects, finding a mix of possible risks, upsides and unknowns. For example, the report said marijuana can ease chemotherapy-related nausea and adults' chronic pain but also found evidence the drug is linked to developing schizophrenia and getting in traffic crashes.
In recent weeks, studies have echoed concerns about high-potency marijuana and psychosis and documented a rise in marijuana-related emergency room visits after legalization in Colorado. Tobacco and marijuana use can also go together. Blunts-marijuana in a cigar wrapper that includes tobacco leaves-have gained popularity. And studies have found more cigarette smokers have used pot, and the other way around, compared to nonsmokers.
"One substance reinforces the use of the other, and vice versa, which can escalate a path to addiction," says Dr. Sterling McPherson, a University of Washington medical professor studying marijuana and tobacco use among teens.
The National Academies report found marijuana use likely increases the risk of dependence on other substances, including tobacco. To some public health officials, it makes sense to legalize marijuana and put some guardrails around it. "For tobacco, we know that it's inherently dangerous and that there is no safe amount of tobacco to use," says New York City Health Department drug policy analyst Rebecca Giglio, whereas with marijuana, "we see this as an opportunity to address the harms of criminalization while also regulating cannabis." But health department opinions vary, even within the same state: New York's Association of County Health Officials opposes legalizing recreational weed.
As most other debates, marijuana versus tobacco, has people standing on both sides of the proverbial fence. As a former cigarette smoker, New Yorker Gary Smith is dismayed that his home state might OK smoking pot. He knows research hasn't tied smoking marijuana to lung cancer, but he fears the respiratory risks of marijuana smoking aren't fully known. And on the other hand, Hawaii physician and state Rep. Richard Creagan feels no less strongly about cigarettes. Meanwhile, he'd like Hawaii to legalize recreational marijuana, an idea that failed to take off in the state Legislature this year.
