Does Marijuana Cause Health Problems?

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

“The popular notion seems to be that marijuana is a harmless pleasure…” But what are the potential adverse effects of marijuana use? That’s not an easy question to answer. Most studies [to date have been] cross-sectional or rely on self-reported health.” Cross-sectional means a snapshot in time; and so, you don’t know which came first. Are people sick because they’re smoking marijuana, or are they smoking marijuana because they’re sick? And, if you just ask people how they are, pot smokers may be like: “I feel great!” even if they’re actually suffering from some health problem. “Few longitudinal studies” have been done—meaning studies done over time, using “objective” measures of health—until, now.

More than a thousand “individuals followed up from birth to age 38,…test[ing] associations between cannabis use over [decades] and multiple domains of physical health…” They looked at 12 health outcomes, and tobacco use “was associated with worse health for 8 of…12…,” from impaired lung function to systemic inflammation, and metabolic derangements. And, cannabis use was associated with—just gum disease. That’s it? “[C]annabis use was unrelated to other physical health problems.”

Now, periodontal disease can lead to tooth loss, and there may be other dental health problems associated with smoking marijuana, but when cannabis is described as “nefarious,” the first thing to come to mind is probably not gingivitis.

Is it possible that cannabis users are just living healthier-than-average lifestyles to counteract the effects of the drug? Like eating more fruits and vegetables, or maybe drinking less alcohol? No, neither are pot smokers exercising any more; and so, “[t]he absence of associations between cannabis use and poor physical midlife health could not be attributed to” any of these other things. So, maybe marijuana is just not that bad.

Heroin may increase your risk of dying, cocaine use may increase your risk of dying; but no association was found between mortality and marijuana. Now, they did just follow these folks until age 38. To find out what happens after that, we need to turn to Sweden, where they recently published “the longest [study ever] on cannabis and mortality:” 50,000 men “followed…up to around age 60.” About 30 years ago, when they first reported on this cohort, “no…significant excess mortality was found” among cannabis users, or abusers as they called them. But, back then, these men were in their 30s, like in that other study.

What happens when you follow them past middle age, when perhaps “the health-related detrimental effects” might begin to emerge? Those with “a history of heavy cannabis use” did end up having “a significantly higher risk of death”—a 40% higher risk of dying prematurely.

But, wait a second. I thought cannabis didn’t kill. Cocaine kills thousands of Americans every year, alcohol kills tens of thousands, and tobacco breaks the graph, wiping out hundreds of thousands of people in the U.S. every year. But, marijuana doesn’t even make it onto the graph.

But, what they’re referring to is that “no deaths have been directly attributed to the acute physical toxicity of cannabis.” So, when some 19-year-old eats a cannabis cookie and then jumps “off a fourth floor balcony,” the direct cause of death was the fall. But, that doesn’t mean cannabis didn’t contribute.

It’s true that people don’t directly OD on cannabis like you can with opiates, which can shut down your breathing. Unlike many pharmaceuticals, for which a harmful dose may just be a few times larger than the prescribed dose, the “therapeutic index” for cannabis is like 40,000 to 1. Does that mean you could smoke like 40,000 joints without OD-ing? No; you may be able to smoke 2 million joints before a lethal overdose. Cannabis use contributes more to disease than death (in part because people aren’t injecting it), but “[t]he health-related harms of cannabis had never been quantified on a global scale”—until, 2013.

Every year, cannabis is estimated to result in two million years of healthy life lost due to disability. Now, this is tiny, compared to 100 million or so years attributed to alcohol or tobacco, but still results in a lot of pain and suffering.

But, what about our gum disease study? I thought the only physical health problems were dental in nature. Well, they were just looking at a specific set of health problems; they emphasize that the periodontal problems are in addition to all the other potential issues, like increased risk of “accidents and injuries, bronchitis, [heart attacks and strokes],…possibly, infectious diseases, and cancer, as well as [the] mental health concerns…” But, in terms of as a more direct cause of death, marijuana may be suspected in maybe hundreds of deaths over an eight-year period, whereas a single pharmaceutical drug—Viagra—was involved in thousands.

Please consider volunteering to help out on the site.

• Volkow ND, Baler RD, Compton WM, Weiss SR. Adverse health effects of marijuana use. N Engl J Med. 2014;370(23):2219-27.
• Meier MH, Caspi A, Cerdá M, et al. Associations between Cannabis Use and Physical Health Problems in Early Midlife: A Longitudinal Comparison of Persistent Cannabis versus Tobacco Users. JAMA psychiatry. 2016;73(7):731-740.
• Greydanus DE, Kaplan G, Baxter LE, Patel DR, Feucht CL. Cannabis: the never-ending, nefarious nepenthe of the 21st century: what should the clinician know?. Dis Mon. 2015;61(4):118-75.
• Walker ER, Pratt LA, Schoenborn CA, Druss BG. Excess mortality among people who report lifetime use of illegal drugs in the United States: A 20-year follow-up of a nationally representative survey. Drug Alcohol Depend. 2017;171:31-38.
• Manrique-garcia E, Ponce de leon A, Dalman C, Andréasson S, Allebeck P. Cannabis, Psychosis, and Mortality: A Cohort Study of 50,373 Swedish Men. Am J Psychiatry. 2016;173(8):790-8.
• Gerich ME, Isfort RW, Brimhall B, Siegel CA. Medical marijuana for digestive disorders: high time to prescribe?. Am J Gastroenterol. 2015;110(2):208-14.
• Barrus DG, Capogrossi KL, Cates SC, et al. Tasty THC: Promises and Challenges of Cannabis Edibles. Methods Rep RTI Press. 2016;2016
• Handcock-Allen JB, Barker L, VanDyke M, Holmes DB. MMWR Morb Mortal Wkly Rep. 2015;64(28):771-2.
• Bostwick JM. Blurred boundaries: the therapeutics and politics of medical marijuana. Mayo Clin Proc. 2012;87(2):172-86.
• Storr M, Devlin S, Kaplan GG, Panaccione R, Andrews CN. Cannabis use provides symptom relief in patients with inflammatory bowel disease but is associated with worse disease prognosis in patients with Crohn's disease. Inflamm Bowel Dis. 2014;20(3):472-80.
• Wilkie G, Sakr B, Rizack T. Medical Marijuana Use in Oncology: A Review. JAMA Oncol. 2016;2(5):670-675
• Degenhardt L, Hall W. Extent of illicit drug use and dependence, and their contribution to the global burden of disease. Lancet. 2012;379(9810):55-70.
• Degenhardt L, Whiteford HA, Ferrari AJ, Baxter AJ, et al. Global burden of disease attributable to illicit drug use and dependence: findings from the Global Burden of Disease Study 2010. 2013;382(9904):1564-74.
• Hall WD. Commentary on Imtiaz et al. (2016): The burden of disease attributable to cannabis-implications for policy. Addiction. 2016;111(4):663-4.
• Nelson B. Cannabis conundrum: evidence of harm?: Opposition to marijuana use is often rooted in arguments about the drug's harm to children and adults, but the scientific evidence is seldom clear-cut. Cancer Cytopathol. 2015;123(1):1-2.

Motion graphics by Avocado Video

• alcohol
• beverages
• cancer
• cannabis
• cardiovascular disease
• dental health
• heart disease
• inflammation
• lifespan
• longevity
• marijuana
• mental health
• mortality
• smoking
• stroke
• tobacco
• Viagra