Cannabis and IBD: What’s the evidence?

Cannabis and IBD: What’s the evidence?

There’s no doubt that many people with IBD report feeling better when using cannabis. Pain, bloating, sleep and appetite often improve, and these anecdotal stories are shared widely online. But the moment you look more closely, it becomes clear this is a complex, and often misunderstood, area.

In this blog, I’ll explore what cannabis actually is, what people may really be using, what the research shows, and why the risks, including something called cannabis hyperemesis syndrome, deserve far more attention than they currently get.

What Are People Really Taking?

When people say “cannabis helps my IBD,” they may not be taking the same thing at all.

In the UK:

• Medical cannabis is legal but extremely rarely prescribed, especially for IBD.

• Most people are using over-the-counter CBD oil, which doesn’t contain enough THC to be considered true cannabis.

• Others may be self-medicating with unregulated THC products purchased illegally, with unknown strains, strength and contaminants.

In other countries, cannabis may be prescribed through regulated systems with proper quality control, but in the UK, the term "cannabis" often refers to a wide range of substances that vary wildly in composition and effect.

What the Research Says

The current research shows that:

• Cannabis may relieve symptoms like pain, sleep disturbances, nausea and appetite loss

• However, it does not reduce inflammation or lead to mucosal healing in the gut

• There is no strong evidence that cannabis or CBD can induce or maintain remission in Crohn’s or colitis

Some small studies (e.g. Naftali et al., 2013; 2021) showed improvement in patient-reported symptoms with THC-rich cannabis but no significant improvement in inflammatory markers or endoscopic findings. Systematic reviews confirm the same: symptom relief yes, disease control no.

Symptom Relief Is Not Disease Control

This distinction is crucial. You may feel better — but that doesn’t mean you’re getting better.

Cannabis can help with:

• Pain perception

• Stress and anxiety

• Appetite stimulation

• Sleep quality

But there’s no clear evidence it:

• Reduces active inflammation

• Promotes gut healing

• Prevents flares or long-term damage

So someone may use cannabis and feel a short-term benefit while their disease continues to progress quietly — which is a serious concern.

The Role of Belief and Placebo

It’s also important to acknowledge that the placebo effect is powerful, especially in conditions like IBD. If someone believes a product will help, that belief can shift pain perception, stress levels and even bowel function.

People often report improvements when starting cannabis or CBD, but without objective inflammatory improvement, this could be a result of expectation, not the product itself. That’s why double-blind, placebo-controlled studies are essential.

Cannabis Hyperemesis Syndrome (CHS)

One of the most overlooked risks, especially in the IBD community, is Cannabis Hyperemesis Syndrome — a condition where chronic cannabis use causes severe, repeated nausea and vomiting.

It often develops in people who’ve been using cannabis daily or nearly daily for months or years. The key features include:

• Unrelenting vomiting (often dozens of times a day)

• Nausea and abdominal pain

• Relief only from hot showers or baths — a hallmark of the condition

Despite cannabis being known for easing nausea in some situations, in CHS it does the opposite. Over time, cannabis disrupts the brain–gut signaling system and appears to worsen gastric emptying and gut motility.

Studies estimate that up to 6 to 30 percent of long-term cannabis users may develop CHS. In emergency departments, one study found that 1 in 3 regular users with vomiting met the criteria. It’s easy to misdiagnose as a flare, particularly when someone has Crohn’s or colitis, and the patient may never suspect cannabis is to blame.

The only real solution is to stop using cannabis completely. Anti-nausea drugs are rarely effective, and symptoms usually return if cannabis use resumes.

For someone with IBD, this is particularly relevant. Repeated vomiting, nausea or cramping should never be dismissed, but if inflammation markers are low and cannabis is being used regularly, CHS needs to be considered.

Final Thoughts

Right now, the evidence does not support cannabis as a treatment for IBD. It may offer some symptom relief, or appear to, but it doesn't reduce inflammation or help the gut to heal. Worse, it can actually cause nausea and vomiting in the form of cannabis hyperemesis syndrome, which many people (including healthcare professionals) still don’t recognize.

Given the risks and the lack of proven benefit, I don’t recommend cannabis for IBD. People deserve strategies that truly support healing — not substances that may only mask symptoms or worsen their condition over time.

Summary

• UK cannabis use for IBD is largely unregulated and misunderstood

• THC may help symptoms, but not inflammation

• CBD alone has shown limited effects, especially at legal doses

• The placebo effect is very real

• Cannabis Hyperemesis Syndrome (CHS) is a serious risk

• More research is needed — but for now, cannabis is not a recommended treatment