Decoding cannabis: Can THC-rich cannabis ease gut symptoms in fibromyalgia?

Titled “The effect of medical cannabis on gastrointestinal symptoms in fibromyalgia and disorders of gut-brain interaction: a patient‑centred real‑world observational study”, it followed 60 fibromyalgia patients over six months as they used a THC-rich medical cannabis oil prescribed in a clinical setting. These were people dealing with both pain and gut discomfort, even after trying a range of conventional treatment options.

• Did it help, and if so, how? 

• Were there side effects? 

• And what does it mean for people trying to manage overlapping fibromyalgia and gut symptoms?

Let’s find out…

Can medical cannabis offer relief for fibromyalgia and gut issues?

It certainly seems so, and that’s backed not just by personal experiences, but by the emerging clinical research.

Many people living with fibromyalgia also deal with digestive symptoms, especially IBS. As interest grows in medical cannabis treatment for fibromyalgia (as it has done in the past decade), THC based medical cannabis oils have become a real focal point for researchers exploring adjunct therapy options, especially for those who haven’t responded to traditional care.

Understanding the link between fibromyalgia and digestive symptoms

In the 2025 study we’re focusing on today, more than 75% of participants had IBS or functional dyspepsia (a type of chronic indigestion). These are both classed as disorders of gut-brain interaction, which means that the communication link between the nervous system and the digestive system isn’t in tune, often leading to pain, discomfort, and unpredictable symptoms without clear physical causes.

This is especially important for people with fibromyalgia, as gut disorders are so often linked, and when both are present, the symptoms of one can worsen the other. 

But why?

Why do fibromyalgia and gut issues often occur together?

Researchers now believe that it has something to do with central sensitisation. This is the term used for when the nervous system becomes extra sensitive, amplifying signals from all over the body. 

Not just pain, but also sensations from the gut, like fullness, indigestion, or discomfort after eating.

Other factors can make these issues worse. Consistently poor sleep, an undercurrent of stress or anxiety, and general unhappiness/depression have all been shown to have an impact on gut health. 

They’re also common in fibromyalgia, so it’s a real double whammy. 

What did the study investigate, and how was cannabis used?

• The study ran for 6 months

• 60 participants signed up

• They were given a high THC, low CBD medical cannabis oil

• The oil was administered sublingually (under the tongue)

• The dose was slowly increased until each participant found symptom relief

• The maximum dose allowed was 20 mg of THC per day

• The researchers surveyed the participants right at the start, and the three months in, and at the six-month endpoint to gauge treatment effectiveness

• They tracked changes in pain, fatigue, gut discomfort, and overall symptom severity using two standardised tools: the Revised Fibromyalgia Impact Questionnaire (FIQR) for fibromyalgia symptoms, and a validated gastrointestinal symptom survey for digestive issues.

Who took part in the study?

The heavy majority of participants (91.7%) were women in their fifties who had been living with fibromyalgia for years. 

Most of the patients suffered from IBS or chronic indigestion alongside fibromyalgia. And the fact that they had already gone through the ringer of conventional pharmaceutical treatment options without any sustained symptom control made them great candidates for this study.

So, what were the findings?

Medical cannabis improved fibromyalgia symptoms over 6 months

There is really no doubt about this finding, in general terms. 

Was it true for every single participant?

No, but for 53 of the 60 participants (that’s 88.33%), improvements were obvious. 

At the start, the average FIQR score was 80.9, a level that reflects a severe impact on daily life. 

By the end of the study, the average score had dropped to 56.6. That’s a massive shift.

That shift meant better function for many participants, and in a few cases, symptoms eased to the point of near-remission. Those who continued treatment throughout the full six months tended to see the strongest gains. 

Which fibromyalgia symptoms improved the most?

Pain levels came down for most participants (83.3%), and many also reported sleeping better and feeling less exhausted (80%). 

These improvements grew stronger between the three and six-month marks. That extra time on treatment seemed to help symptoms settle. Many also said their overall quality of life had improved by the end of the study.

What does this suggest about cannabis as a treatment?

The slow but consistent trend towards less pain, better sleep, and a decrease in gut issues are indicative of what we see every day here at Releaf - that is, that medical cannabis treatment rarely offers an overnight fix. 

People battling long term, chronic conditions most often find that improvements come in small incremental steps. 

So if you are looking to add medical cannabis to your current treatment regime, it’s best to not expect any sudden shifts. Over weeks and months, symptoms start to ease, routines become more manageable, and quality of life begins to improve. 

This study reflects that same pattern. 

THC oil helped reduce bloating, stomach pain, and upper GI symptoms

Patients in the study reported steady relief from some of the most frustrating, hard to treat gut symptoms.

Bloating became less intense, as did general stomach pain. The upper-abdomen, acid like discomfort which patients with functional dyspepsia often report was also reduced for many of the participants.

By the six-month mark, many participants described more manageable digestion and fewer daily flare-ups. 

But, somewhat interestingly, the treatment didn’t seem to affect how often people went to the toilet, or what their daily bathroom patterns looked like. That points to a change in how the gut feels, but not necessarily how it actually digests.

Which gut issues did not respond?

The treatment didn’t seem to make much difference to stool patterns or post-meal fullness. That may suggest cannabis has more of an effect on gut sensitivity than on motility. In those cases, other types of treatment may still be needed.

How well was THC-rich medical cannabis oil tolerated in the study?

The majority of people in the study responded very well to the cannabis oil. Some experienced side effects, but for most, they were mild and manageable. The most common ones were daytime sleepiness, brief periods of brain fog or confusion, and the occasional headache.

Three patients decided to stop treatment because of how those effects felt in daily life. Another four didn’t feel the oil was helping and chose not to continue, bringing the total dropout number to seven.

Importantly, no one reported worsening gut symptoms or any serious side effects linked to the digestive system itself.

How did patients respond overall?

Just 7 of the patients chose to leave the study early (3 due to side effects, and 4 due to finding the treatment ineffective).

The rest stayed on treatment and slowly adjusted their dosage over time. Most reported feeling more comfortable as the weeks went on, with the majority finding high levels of symptom control and better overall quality of life. 

When should you consider UK medical cannabis treatment for fibromyalgia and IBS?

If you’re one of the thousands of UK residents that has been through a cycle of prescriptions, referrals, and recommendations without finding symptom control, you’re not alone. 

In the UK, private medical cannabis prescriptions are an option for adults who’ve already tried at least two conventional treatments without success. It’s not a first line treatment option, but when pain, bloating, or fatigue continue despite your best efforts, a medical cannabis prescription through Releaf may be the best next step forward. 

If this sounds like you (or a loved one), then feel free to head to our medical cannabis eligibility checker. It takes less than 20 seconds to complete, costs absolutely nothing, and is designed to quickly give you a clear answer on whether medical cannabis might be an option for your health needs.