Cannabis is not a treatment for colon cancer or any colon disease: CBD reduced precancerous growths in mice, but no human trial has shown that cannabis prevents or treats colorectal cancer. In people, studies show that THC relaxes the colon and slows its contractions, and cannabinoids may ease chemotherapy nausea. For inflammatory bowel disease, Cochrane reviews found no firm conclusions.
The colon comes up in cannabis research in three ways: colorectal cancer, how cannabinoids affect gut movement, and inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis. This page covers all three, with the strongest human evidence first, as of October 2026. It is part of our overview of cannabis and cancer research.
Evidence at a Glance
| Claim | Evidence level | Source |
|---|---|---|
| CBD prevents colon tumors | Preclinical only (mice) | Aviello 2012 |
| Cannabinoids kill colon cancer cells | Preclinical only (cell lines) | Cianchi 2008 |
| Cannabis treats colorectal cancer in people | No human evidence | ASCO 2024 |
| THC relaxes the colon and reduces contractions after meals | Limited (one randomized trial in 52 healthy volunteers) | Esfandyari 2007 |
| Cannabis induces remission in Crohn’s disease or ulcerative colitis | Very low to moderate quality; no firm conclusions | Kafil 2020 (Cochrane) |
| Cannabinoids ease refractory chemotherapy nausea | Strong; FDA-approved drugs | FDA |
Cannabis and Colon Cancer: What Lab Studies Show
Colorectal cancer is one of the most common cancers in the US, and the colon is full of cannabinoid receptors, which control gut movement and inflammation. That has made it a natural target for lab research.
- CBD in a mouse model (2012). Italian researchers gave mice a chemical that causes colon cancer. Mice treated with CBD developed fewer precancerous lesions, polyps and tumors. In colon cancer cell lines, CBD protected DNA from oxidative damage and slowed cell growth.
- Cannabinoid receptors and cell death (2008). Another Italian team found that activating cannabinoid receptors triggered programmed cell death in colon cancer cells through a ceramide pathway.
When you see a headline that “cannabis kills colon cancer cells,” check whether the study used cells, mice or people. So far it has always been cells or mice. Our guide to cannabis and tumors explains why those results often fail to carry over to human patients, including high doses and direct delivery that a person using cannabis would never reach.
NCI’s PDQ summary lists colon cancer among the tumors where CBD showed preventive effects in animals. These findings support more research. They do not show that cannabis prevents or treats colon cancer in people.
Is There Human Evidence for Colorectal Cancer?
No. There are no published randomized trials of cannabis, THC or CBD as a treatment for colorectal cancer. The National Academies found insufficient evidence that cannabinoids treat any cancer, and its 2017 review did not reach any conclusion on whether cannabis use raises or lowers colorectal cancer risk. ASCO’s 2024 guideline advises against cannabis as a cancer-directed treatment outside a clinical trial. The proven ways to lower colon cancer risk remain screening, which can find and remove polyps before they turn cancerous, along with not smoking, limiting alcohol and staying active.
How THC Affects the Colon: The Mayo Clinic Study
The most solid human research on cannabis and the colon is about function, not cancer. In a randomized, placebo-controlled study at the Mayo Clinic, 52 healthy volunteers took a single 7.5 mg dose of dronabinol (synthetic THC) or a placebo. Researchers measured colon pressure and tone with a balloon device before and after the dose and after a 1,000-calorie meal.
Dronabinol relaxed the colon, increased its compliance (how much it stretches), and reduced the contractions and tone that normally follow a meal. Volunteers also rated distension as more painful, which the authors suggested reflects THC’s effect on how the brain processes gut signals. The researchers proposed further study in diarrhea-predominant conditions such as irritable bowel syndrome. The practical takeaway: THC slows the gut. That can help some people and cause constipation or bloating in others.
Cannabis for Crohn’s Disease and Ulcerative Colitis
Many people with inflammatory bowel disease use cannabis for pain, cramping and appetite. Cochrane reviews of the trials, summarized in a 2020 paper in Inflammatory Bowel Diseases, found that in one ulcerative colitis trial of 60 people, 24% on cannabis oil reached remission compared with 26% on placebo. Crohn’s trials were small, and side effects were more common with cannabis. The authors concluded that no firm conclusions can be drawn about safety or effectiveness. Some patients report feeling better, but there is no evidence that cannabis heals the inflamed bowel.
Symptom Relief During Colon Cancer Treatment
- Nausea and vomiting. The FDA approved dronabinol and nabilone for chemotherapy nausea and vomiting that standard antiemetics have not controlled. ASCO supports cannabinoids as an add-on for refractory nausea.
- Nerve damage from oxaliplatin. Oxaliplatin, a common colon cancer drug, often causes numbness and tingling. NCI’s summary cites a retrospective Israeli study that found lower rates of moderate-to-severe neuropathy in cannabis users, but small randomized trials of cannabinoids for chemotherapy neuropathy found no significant benefit.
- Diarrhea. THC’s slowing effect on the colon could in theory ease treatment-related diarrhea, but this has not been tested in cancer patients.
- Pain and appetite. A 2023 Cochrane review found cannabinoids did not beat placebo for opioid-resistant cancer pain, and appetite trials have been mostly negative.
Risks and Side Effects
- Cannabinoid hyperemesis syndrome. Long-term heavy use can cause repeated bouts of severe vomiting and abdominal pain, according to NIDA. It is easy to mistake for a bowel problem.
- Masking symptoms. Using cannabis to manage cramping or bleeding can delay a diagnosis. Rectal bleeding, a change in bowel habits or unexplained weight loss needs a doctor, not a dispensary.
- Constipation and bloating from slowed gut movement, especially combined with opioids.
- Drug interactions. CBD inhibits liver enzymes that process many drugs. NCI warns that concentrated CBD oils could change chemotherapy toxicity or effect. Observational studies have also linked cannabis to lower response to immunotherapy, which is used in some colorectal cancers.
- Drowsiness and dizziness, which add to treatment fatigue.
Talk to Your Doctor
If you have colon cancer or inflammatory bowel disease and want to try cannabis, ask your oncologist or gastroenterologist first. Bring the product label, ask about interactions with your chemotherapy or biologic drugs, and ask whether a prescription cannabinoid fits your nausea. If you are of screening age, or have symptoms, get screened. Our guides to tinctures and smoke-free cannabis explain the alternatives to smoking if your doctor agrees.
Cannabis and Colon FAQ
Can cannabis cure colon cancer?
No. CBD reduced colon tumors in mice, but no human trial has shown that cannabis prevents or treats colorectal cancer.
Does marijuana slow down the colon?
Yes. In a Mayo Clinic trial, a single dose of dronabinol (synthetic THC) relaxed the colon and reduced its contractions after a meal.
Does cannabis help Crohn’s disease or ulcerative colitis?
Some people report symptom relief, but Cochrane reviews found no firm evidence that cannabis induces remission, and side effects were more common than with placebo.
Can cannabis cause stomach and bowel problems?
Yes. Heavy long-term use can cause cannabinoid hyperemesis syndrome, with cycles of severe vomiting and abdominal pain, and THC can cause constipation.
Can I use cannabis during colon cancer chemotherapy?
Only with your oncologist’s knowledge. Prescription cannabinoids are approved for refractory chemotherapy nausea, but CBD can interact with drug metabolism.
For adults 21+ in legal states. General information, not medical advice. Talk to a doctor before using cannabis for a health condition.
