Decoding Cannabis: Can medical cannabis support gut issues (nausea, IBS, IBD) and digestion?

While we’ve mapped much of the gastrointestinal tract in truly microscopic detail, health concerns like Irritable Bowel Syndrome (IBS), Inflammatory Bowel Disease (IBD), Crohn's Disease, Ulcerative Colitis, and even persistent nausea, still leave far too many patients cycling through treatments that don’t always bring long-term relief, or even work at all. 

And so, somewhat unsurprisingly, increasing numbers of UK patients are turning to medical cannabis in the hope of finding relief where conventional treatments have come up short. It isn't going to cure any gastroenterological conditions, but medical cannabis can help to ease digestive symptoms for many patients. 

With World Digestive Health Day being observed, we thought it was the perfect time to dissect this comprehensive review from 2021 in our Decoding Cannabis blog series. 

Titled “Role of Cannabis and Its Derivatives in Gastrointestinal and Hepatic Disease”, this overarching review brings together findings from over 100 studies (including lab research, clinical trials, and real-world patient data) and digs into the relationship between cannabis, digestion, and gastrointestinal disorders - unpacked here in a format that’s a little more approachable than your average clinical review. 

The authors of this report set out to better understand how cannabinoids interact with the endocannabinoid system in the gut, and what that means for things like motility, the microbiome, and chronic gastroenterological conditions such as IBS, IBD, nausea, and constipation.

What did they find? It’s all here…

How the endocannabinoid system (ECS) supports digestion and gut health

Deep inside the gut, the body is quietly regulating movement, mood, immune activity, and appetite, and the endocannabinoid system plays a big part in that. This system, often abbreviated to the ECS, includes:

• Two receptors - CB1 and CB2

• The body’s very own cannabis-like compounds which are called endocannabinoids

• Enzymes that control endocannabinoid levels

Put simply, endocannabinoids act as chemical messengers. They help cells talk to each other and keep the gut’s rhythm “steady”. What makes the Cannabis sativa L. genus (cannabis and hemp plants) so interesting from a medical standpoint is the cannabinoids it produces. 

Cannabinoids like THC and CBD  are structurally similar to the body’s own endocannabinoids. That likeness gives them a way in, letting them influence the system gently at times, and more noticeably at others.

How does cannabis interact with the endocannabinoid system?

CB1 receptors are found in the gut wall and make up a major part of the nerves that control digestion. They help regulate gut motility, secretion, and pain sensitivity. Meanwhile, CB2 receptors take a bit of a backseat and help regulate the immune response through controlling levels of inflammation. 

THC can bind directly to the CB1 receptors, which can slow digestion, ease nausea, and increase appetite. CBD doesn't plug into either receptor type as strongly, but research shows that it keeps our endocannabinoids active for longer by blocking the enzymes that usually break them down.

The fact is, we all produce endocannabinoids at different levels, and, no two cannabis cultivars are quite the same. The effects of medical cannabis flower administration can vary a great deal from patient to patient, which is why the prescribing of medical cannabis needs to have direct clinical oversight. 

This oversight doesn’t only involve the particular condition, but symptom pattern, the patient’s personal medical history, and the CBMP type and administration method. What works for one patient may be ineffective, or potentially counterproductive, for another - that’s why medical oversight matters.

At Releaf, every prescription is personalised, overseen by our world-class clinical team, with all prescriptions signed off on by specialist doctors on the GMC specialist register. If you would like to learn more about medical cannabis and whether it may be right for you, start with our medical cannabis eligibility checker. It's fast, free, and takes less than 20 seconds to complete.

How cannabis interacts with specific digestive conditions

Beyond lab findings or theoretical posturing, the review turned its attention to real-world digestive issues. It drew from clinical studies and patient-reported data to assess how cannabis may affect the symptoms that so many of us deal with day to day. 

In each case, it asked where cannabinoids had helped, where they hadn’t, where the outcome seemed to depend on the person or the dose, or how the treatment was taken. The picture wasn’t definitive, but it was detailed, and the results offer a clearer picture of where cannabis might have a role to play.

Can medical cannabis help with nausea, or does it make it worse?

Medical cannabis for chemotherapy-induced nausea and vomiting is one of the few uses currently recognised by the NHS. But in practice, access is extremely limited. Prescriptions are rarely given, and only within strict oncology settings.

For most patients, especially those whose symptoms don’t quite fit the criteria, private clinics remain the more realistic option. Here, treatment can be shaped around the individual rather than forced into a narrow guideline.

This anti-nausea effect is likely due to THC’s ability to activate CB1 receptors in the brain stem, particularly in the parts of the brain and central nervous system that control triggering the vomiting reflex.

The research paper also showed that the endocannabinoid system doesn’t just block signals at the surface, it also modulates deeper processes that drive nausea. It reduces the release of neurotransmitters (serotonin and substance P), which are involved in how nauseous we feel. 

Together, these mechanisms explain why THC can be effective against even severe nausea, especially when other medications fail.

But the review also highlighted a more complicated picture. 

In a small subsection of people who have taken high THC cannabis for long periods (usually without clinical oversight), a condition referred to as cannabinoid hyperemesis syndrome (CHS) can pop up. People with CHS experience repeated bouts of nausea and vomiting that come in cycles and often do not respond to standard anti-nausea medications.

Although uncommon, cases of CHS are a clear reminder that cannabis doesn’t work the same way for everyone. In some cases, especially with long-term use of high-THC products, the effects can shift - often in ways that are difficult to predict. 

It’s one more reason why clinical guidance matters, not just for safety, but to help ensure that treatment stays effective over time.

Does medical cannabis help with gut pain and cramping?

For most people with IBS or IBD, gut pain is more than a simple inconvenience. It’s the major symptom that tends to overshadow everything else, the one that often drives patients to seek alternative treatment options when conventional routes have failed.

When long bouts of pain and cramping become part of daily life, they can start to bleed into everything else. Mood and motivation dips, sleep gets disrupted, appetite fades, and this can quickly chip away overall quality of life.

The review looked at whether specific cannabinoids could help ease that kind of pain. Not by numbing it entirely, but by shifting how the body senses discomfort, dampening inflammation, and softening the edges of an overreactive gut.

As we’ve already touched on, THC interacts most directly with the endocannabinoid system. It binds to CB1 receptors, which helps dial down how the gut senses pain. CB2, which becomes more active during inflammation, may help settle immune overactivity and reduce cramping caused by mast cells (immune cells that release chemicals known to irritate the gut).

CBD takes a quieter route. It doesn’t latch onto receptors in the same way, but it does block an enzyme called FAAH, which normally breaks down the body’s natural endocannabinoids. When this process slows, those chemical messengers stick around longer, which might help take the edge off heightened gut sensitivity.

The clinical picture isn’t complete, but the biological rationale is there. And while more trials are needed, it may help explain why so many patients with chronic gut issues report finding relief through medical cannabis.

What have studies shown about cannabis for IBS symptoms?

IBS is messy. It’s rarely just one thing going wrong - you’ve got gut sensitivity, irregular motility, low-grade inflammation, and often an unhappy microbiome all at once. That mix makes it tricky to treat and even harder to study.

The review looked at several trials involving cannabinoids, especially dronabinol (a synthetic form of THC). In patients with diarrhoea-heavy or mixed-type IBS, dronabinol seemed to slow down gut motility. That’s potentially helpful for people dealing with urgency or frequent bowel movements.

But not everyone saw results. Some studies showed mild symptom relief, others didn’t show much change at all. Part of this inconsistency is thought to come down to genetics, particularly differences in the genes that control CB1 receptors and the FAAH enzyme. These can affect how the body responds to cannabinoids in the first place.

Even so, patient feedback tells a slightly different story. 

Many report less cramping, fewer flare-ups, and a general sense that things are more manageable. The evidence is still early, but there’s a signal here worth following.

As Omar, a Releaf patient, puts it:

“The great thing about my doctor at Releaf is that she really understands that my condition is not just about pain. IBS is very complicated: it is as much a mental thing as it is physical, because once the pain starts, I can get worked up emotionally, and then my muscles that tense up and things go downhill from there. I’d always suspected that what I really needed was more than just pain relief. I needed a medicine that would work in a multi-faceted kind of way: something that would relax my muscles, but would also affect my mood, disassociating me from the pain, preventing that negative, psychosomatic response. 

My vape pen and the flower are great for those stressful moments. If I'm not in a full-blown flare-up—if I’m just starting to feel discomfort versus real pain—I start to get worried that a full-blown flare-up is imminent, and things spiral down from there. When I have those feelings, the flower allows me to kind of take the edge off, so things don’t spin out of control. It’s something I can take that isn't going to disrupt my day and isn't going to influence my cognitive functioning.

The cannabis oil is different. It’s my last resort—for when the pain gets very bad—and I take quite a high dose. It's the only thing that has allowed me to sleep through the pain at night, and the length of time that I’m in pain is shortened from four, five or six days to one or two days maximum. That was a huge improvement

I’ve been a patient at Releaf for three months, and I think my doctors and I have found a healthy balance with the treatment: the flare-ups are managed by the cannabis oil, and the discomfort is managed by the flower.”

Is cannabis effective for IBD, Crohn’s, or ulcerative colitis?

Crohn’s and ulcerative colitis aren’t just painful conditions, they’re relentless. The immune system stays locked in a long, draining battle with the gut lining, leading to inflammation, fatigue, and often a string of treatments that don’t quite work.

The review noted that during gut inflammation, the endocannabinoid system seems to ramp up. CB2 receptors in particular become more active on immune cells. That’s where cannabinoids might step in to help settle things down.

People taking medical cannabis in observational studies reported better appetite, sleep, and less pain. But when researchers looked for changes in inflammation itself, the results were mixed. Randomised trials showed that while people felt better on cannabis, it didn’t always show up in the biomarkers doctors usually track.

Does the route of administration matter?

The authors also pointed out that inhaled cannabis was more effective than capsules or swallowed oils. When inhaled, medical cannabis gets to work much faster than when swallowed, providing faster relief from symptoms like pain and cramping. This immediate effect can be especially useful during flare-ups.

When swallowed, medical cannabis oils/capsules have to travel through the digestive tract, where absorption and effectiveness are both influenced by digestion, gut motility, and inflammation - the effects take anywhere between 45 and 90 minutes to be felt, and can vary from one day to the next depending on what’s happening in the gut.

While the review focused on swallowed oils, it is important to point out that medical cannabis oil taken sublingually (absorbed under the tongue) avoids the digestive tract and offers higher and more consistent rates of cannabinoid absorption. The review highlighted that the route of administration is a key factor in treatment effectiveness, something that our specialists take into account with all Releaf patients.

THC and CBD both appear to have roles to play, but the effects depend on dose, delivery method, and the individual patient. In short, cannabis is not a cure, but for many with IBD, it could be a useful addition to the wider treatment toolkit.

Could medical cannabis offer relief for gut issues like IBS, IBD, or nausea?

Digestive disorders like IBS, IBD, and chronic nausea are notoriously difficult to treat, deeply personal, and often poorly served by conventional pharmaceutical options. 

What this review made clear is that medical cannabis has the potential to offer symptomatic relief, not just by masking discomfort, but by working through biological pathways we’re beginning to understand in more detail. While the science is still evolving, the clinical rationale is strong. For patients who haven’t found success elsewhere, it’s a path worth considering.

If you’re keen to learn more about the potential that medical cannabis offers, the first step is simple. Head to our medical cannabis eligibility checker  - it’s free, takes under 20 seconds, and connects you with specialist doctors who understand your condition and how to treat it safely with both conventional and cannabinoid-based care.