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In recent years there’s been a growing interest in the use of cannabis — both marijuana and CBD products — to help treat a number of health conditions, including gastrointestinal disorders.
Some cannabis products are marketed as a method to help ease health conditions like irritable bowel syndrome (IBS), as well as Crohn’s disease and ulcerative colitis, both forms of inflammatory bowel disease (IBD).
And people with these conditions have taken note. A study published in August 2018 in the Journal of Pediatrics found that nearly a third of the adolescents and young adults with IBD surveyed had used marijuana. Of these, 57 percent endorsed its use for at least one medical reason (most popularly to help with pain).
But do these claims hold any merit or are they just hype? Here, we break down what the science says about cannabis use and its effect on the gut.
Understanding How Cannabis Works in the Body
Cannabis refers to all of the products derived from the plant Cannabis sativa. This plant contains more than a hundred substances called cannabinoids. The two most common cannabinoids are CBD (cannabidiol) and THC (tetrahydrocannabinol). THC has psychoactive effects that make people feel “high,” while CBD does not.
Both THC and CBD are being studied for medical benefits because of their effects on the endocannabinoid system, a complex network of chemical signals and cell receptors that naturally occur in the body.
“The endocannabinoid system was discovered in the 1990s, and researchers were able to see that cannabinoids act at multiple receptors throughout the body, with two main receptors called the cannabinoid receptor one (CB1) and cannabinoid receptor two (CB2),” says Jami Kinnucan, MD, senior associate consultant in the section of gastroenterology and hepatology at Mayo Clinic in Jacksonville, Florida. “So that's why we can maybe hypothesize that they [cannabinoids] might have impacts in various medical conditions and/or symptoms.”
CB1 receptors are mainly in the brain and central nervous system, while CB2 receptors are found throughout the rest of the body, including the digestive tract.
What Research Says About the Effects of Cannabis on the Gut
Some research suggests cannabis use can be beneficial for symptoms of gastrointestinal disorders.
A small study published in February 2021 in the journal PLoS One, for example, found that using cannabis for eight weeks was associated with an improvement in symptoms and quality of life in individuals with mild to moderate ulcerative colitis when compared to a placebo. However, it was not associated with decreased inflammation, which would indicate disease improvement.
Similarly, a review of 20 studies published in the Journal of Clinical Gastroenteroloy in October 2021 concluded that while the use of cannabinoids in people with IBD was not effective at inducing remission, it was associated with patient-reported symptom improvement, including decreased abdominal pain, diarrhea, and nausea.
However, research in this area is still limited and several hurdles exist to studying the effects of cannabis on the gut in a robust way. For instance, cannabis can come in so many different formulations and strains. “So when patients are using cannabis, one patient may be using a different strain from the patient next door,” Dr. Kinnucan says.
“One would also argue that it's really hard to find an adequate placebo for cannabis because of the psychoactive effects related to THC,” she continued. “So it makes it very hard to interpret studies.”
Cannabis and the Gut Microbiome
Some early research also raises questions about the effects of cannabis on the gut microbiome, a community of trillions of bacteria and other microbes in the digestive tract that play an important role in overall health. Some of these bacteria are “friendly,” while others, if given the chance to thrive, are harmful. In a healthy person, these bacteria coexist without problems, but a disturbance to this balance may lead to health problems and make an individual more susceptible to disease.
A study in mice published in May 2020 in the Journal of Dietary Supplements found that when taken orally, CBD can lead to an increase in the gut bacteria. But when taken at high doses, CBD disrupted the rodents’ microbiome, putting them at risk for leaky gut syndrome.
While the study was performed in mice and not humans, study author Igor Koturbash, MD, PhD, an associate professor and chair of environmental health sciences at the University of Arkansas for Medical Sciences, says it prompts the need for more studies to better understand the effects of cannabis on the gut and overall health.
“To summarize the study, we found that CBD has potential to sell as a probiotic, but it's a very fine line and scientists need to find at which stage is it beneficial for health and at which stage it's probably not,” he says.
Other Considerations for Cannabis Use
Cannabis containing THC produces psychoactive effects that some people may find unsettling. These can include altered senses and sense of time, mood changes, difficulty with thinking and memory, and impaired body movement. When taken in high doses, it can also lead to hallucinations, delusions, and psychosis.
In some instances, long-term marijuana use can lead to cannabinoid hyperemesis syndrome, characterized by severe nausea, vomiting, and dehydration.
For people purchasing CBD products, Dr. Koturbash notes that since there is no federal regulation of these products, you may be getting much lower or much higher doses than what is on the label.
“For most of the products that are on the U.S. market that are labeled as ‘CBD’ or ‘hemp,’ there is very little to no control over these products, so no one really knows what's inside them,” he says.
If you’re thinking about using cannabis for gastrointestinal symptoms, Kinnucan recommends speaking with your doctor.
“I think that having an open dialogue with a provider about the desire to utilize cannabinoids in the treatment of symptoms is really going to be an important discussion to prevent negative outcomes,” she says.