Medical marijuana: risks and benefits, according to research

By Naveed Saleh, MD, MS
Published August 20, 2021

Key Takeaways

At this point, marijuana has suffused much of American society. According to Statista, sales of marijuana in the United States were estimated at $7.1 billion in 2020—and could mushroom to $37.3 billion by 2024. Currently, the use of recreational marijuana is legal in 18 states and Washington, DC, whereas medical marijuana is legal in 37 states.

Medical marijuana has been used to treat nausea, pain, glaucoma, mental health disorders, seizures, cancer, multiple sclerosis (MS), and other conditions, but with a few exceptions, it has not been scientifically proven to be effective. Research is ongoing.

Meanwhile, one area that has received attention is the use of marijuana as a palliative measure to control nausea and vomiting caused by cancer chemotherapy. But, the relationship between cancer and marijuana is complex. Let’s take a closer look.

Medical marijuana

To begin with, let’s get our marijuana terminology straight. Marijuana and cannabis are often used interchangeably, but technically, they're not the same thing. 

Cannabis refers to all products derived from the plant Cannabis sativa, which contains hundreds of chemical substances called cannabinoids—the most common of which are THC and cannabidiol (CBD). Marijuana, on the other hand, refers to the parts of the plant that contain THC, the psychoactive component that brings about the “high,” or mind-altering state.

The NIH acknowledges the potential for constituents of marijuana to heal—THC does have proven medical benefits in specific formulations. THC-based medications approved by the FDA include dronabinol (Marinol) and nabilone (Cesamet), which are prescribed to treat nausea in chemotherapy patients, as well as wasting syndrome secondary to AIDS. The FDA also approved cannabidiol (Epidiolex) in 2018 for treating seizures associated with two rare and severe forms of epilepsy, Lennox-Gastaut syndrome and Dravet syndrome.

Although the active ingredient THC may be an effective treatment for some conditions, marijuana in its whole plant form presents challenges as it relates to treatment, according to the NIH. 

“Researchers generally consider medications like these, which use purified chemicals derived from or based on those in the marijuana plant, to be more promising therapeutically than use of the whole marijuana plant or its crude extracts,” notes the NIH. “Development of drugs from botanicals such as the marijuana plant poses numerous challenges. Botanicals may contain hundreds of unknown, active chemicals, and it can be difficult to develop a product with accurate and consistent doses of these chemicals.”

Despite such concerns, 18 states have gone “all-in” on greenlighting the use of marijuana by adults. These days, marijuana can be smoked, eaten, inhaled as a mist, applied as a topical on the skin, or taken as a tincture. But, just because voters in various states across the Union have embraced the drug doesn’t mean that it is a risk-free endeavor—especially when it comes to vulnerable populations. 

Marijuana carries risks associated with smoking, and THC can lead to cognitive impairment. It’s also unclear how marijuana interacts with medical conditions, including AIDS, heart disease, MS, and other forms of neurodegenerative disease. It remains to be elucidated how marijuana interacts with chemotherapy. Click here to learn more about how marijuana interacts with prescription drugs, on MDLinx.

Lung pollution

Much like tobacco smoke, marijuana is an irritant to the throat and lungs, and causes cough. It contains tar and volatile chemicals that could raise the risk of cancer and lung disease. 

According to the NIH, inhaled marijuana smoke is linked to large airway inflammation, higher airway resistance, and lung hyperinflation. People who regularly toke experience chronic bronchitis, and are more likely to seek outpatient treatment, according to the research. Other concerns presented by the NIH include immunosuppressive effects on the respiratory system, as well as the increased risk of lung infections such as pneumonia.

As a physician, it probably comes as no surprise that inflammation, infection, and immunosuppression are closely tied to cancer.

“The lung is a site for repeated or chronic inflammatory insults. Epidemiologic research has provided evidence to support the hypothesis that tissue damage caused by inflammation can initiate or promote the development of lung cancer, possibly in conjunction with tobacco use," writes the author of an oft-cited review. "[S]ome studies suggest an increased risk of lung cancer among persons with lung infections, such as tuberculosis, bacterial pneumonia, or inflammatory lung diseases. Elevated serum levels of C-reactive protein, an inflammation marker, are associated with heightened lung cancer risk.”

Cancer of the nether regions

Based on observational studies, experts have hypothesized for some time that marijuana could raise the risk of testicular cancer. In a recent meta-analysis, authors took this association a step further to examine whether cannabinoid compounds themselves can be implicated in the development of nonseminomatous testicular germ cell tumors (TGCTs).

The authors found a summary odds ratio between marijuana use and nonseminoma of 1.71. In other results, they also found that tobacco smoke was related to nonseminoma.

“Available data accord with positive associations between incident TGCT and each exposure, implicating both cannabinoid compounds and other constituents of smoke,” concluded the authors. "Etiologic interpretation awaits epidemiologic studies that assess associations between tobacco smoking and nonseminomatous TGCT, investigating not only these exposures but also both co-use of tobacco and marijuana and smoke-free sources of cannabinoids, while adequately evaluating potential confounding among all of these exposures.”

Bottom line

No matter how many voters embrace the use of recreational and medical marijuana, one truth remains: Smoke is smoke. Smoke contains tar and other noxious components which are tied to the pathogenesis of lung cancer. Although smoking marijuana may ease the discomfort of chemotherapy and cancer, it’s also unclear how it reacts with chemotherapy. Finally, cannabinoids on their own may have carcinogenic potential. 

Meanwhile, in addition to the above-mentioned uses of medical marijuana, research continues on whether this treatment can be effective in treating other conditions like Alzheimer disease, eating disorders, Crohn disease, and epilepsy.

Read more about marijuana’s unexpected effects on sex, and emerging research that links the drug with adverse cardiovascular effects.

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