Is there any evidence cannabis oil (cannabidiol) is useful with ulcerative colitis?

Is there any evidence cannabis oil (cannabidiol) is useful with UC?

Our honorary medical director - Dr Richard Hansen - answers this question.

Dr Hansen is a Consultant Paediatric Gastroenterologist and Honorary Clinical Associate Professor, Glasgow Children’s Hospital.

It’s easy to see why - most people understand what cannabis is as a drug, and there’s been a huge amount of press recently about the availability of cannabis-derived drugs for the treatment of difficult epilepsy. There are two things to cover before we get to the evidence in IBD. Firstly the catch-all term of ‘cannabis oil’ encompasses a lot of different products with varying amounts and types of active ingredients, some legal and some not legal (depending on tetrahydrocannabinol content). So not all cannabis oil is equivalent to all others. Secondly, testing specific compounds and their usefulness within a specific medical condition is tricky, time consuming, and usually very expensive. So generalising any data from one product to a whole class of products or their derivatives is hugely difficult.

The standard way to look for evidence of effect in any drug-based therapy in medicine is by comparing it head-to-head in a trial with either a dummy product (placebo) or a competitor. The comparator is known as a control and so this is known as a control trial. To eliminate bias in testing, the best way to do so is to blind both the patient receiving the therapy and the doctor/researcher assessing the impact. If this doesn’t happen, the patient might perceive benefit or side-effects that are not actually caused by the drug (placebo effect). The observer may subconsciously assess benefit as a result of wanting to see a benefit in their patient. So in a good quality study, blinding can be single-blind or double-blind, depending on who knows what’s been assessed. One final comment is that to assess something fairly, the chances of receiving the test drug or the control product should be left up to chance and not decided based on disease severity or who came to clinic on Thursday. The way to do this is by randomising the treatment received. So the gold standard test is a double-blind, placebo controlled randomised study. It often amazes me that people will see a news item or blog piece on a therapy and immediately look at whether it’s possible to start the treatment or not.

If this isn’t present, important questions should be asked about why. This is how infliximab came to transform IBD care for thousands of sufferers worldwide for instance.

So, let’s take this approach to cannabis and UC... in fact, the Cochrane collaboration already did this for us in November, identifying one double-blind, placebo-controlled randomised study and another placebo-controlled randomised study with issues related to blinding because of the psychoactive effects of the product being tested. I should say, Cochrane seeks to provide an even higher level of evidence for medical treatment by bringing together the results of all studies published on a topic, combining their results if possible. Their conclusion?

“The effects of cannabis and cannabidiol on UC are uncertain, thus no firm conclusions regarding the efficacy and safety of cannabis or cannabidiol in adults with active UC can be drawn. There is no evidence for cannabis or cannabinoid use for maintenance of remission in UC. Further studies with a larger number of patients are required to assess the effects of cannabis in UC patients with active and quiescent disease. Different doses of cannabis and routes of administration should be investigated. Lastly, followup is needed to assess the long term safety outcomes of frequent cannabis use.”

I can’t say fairer than that. Is there an argument for testing cannabis products in IBD? Absolutely, but it’s important it’s done in a robust and scientific manner. Until then, the jury’s out.

https://www.cochrane.org/CD012954/IBD_cannabis-andcannabis-oil-treatment-ulcerativecolitis