Cannabis and Pain — What we Know and What we Don’t

Key takeaways.

When it comes to cannabis and the treatment of pain, it’s a mixed bag of controversy, uncertainties and varied anecdotal stories. Though there is a frivolous hype about cannabis and its potential to reduce pain, there’s a lot of people it doesn’t work for. It’s because pain is the most generalised symptom of disease. Virtually every disease has some aspect of pain, all of them originating from different sources and causes. And that’s why cannabis works for some kinds of pain and not others.

It’s really hard to talk about cannabis and “generalised pain” because often, there is a reason for the pain. For example, if you’ve got the flu, a sore throat is caused by inflammation of the mucous membranes in your throat. And the inflammation is caused by the virus. Cannabis might not necessarily have pain relieving effects for that kind of viral inflammation. 

Because of this nuance in differentiating pain, we’re going to talk about cannabis in terms of its pain (or not) relieving effects in certain diseases. We’re going to cover some of the most common such as cancer-related pain, fibromyalgia-related pain, irritable bowel-related pain, and lastly, we’ll touch on chronic pain.

Differentiating pain.

As we briefly explained, not all pain is created equal. Part of the doctor’s skill is in differentiating pain. For certain kinds of pain, simply removing the source is all that’s required to calm the pain. Like in the example we mentioned, if the pain is a sore throat, dealing with the virus or bacterial infection will remove the pain. In these cases, a pain killer isn’t often required.

Pain is usually differentiated into two forms; “nociceptive” and “neuropathic”.  The first refers to sensory pain in the tissues while in the second, the nervous system is the source of the pain. Examples of nociceptive pain include an injury or a headache, while examples of neuropathic pain include phantom pain after an amputation or the kind of generalised pain that sometimes happens idiopathically in fibromyalgia and chronic pain.

Naturally, these different kinds of pain are treated differently. Some neuropathic pains are treated with psychotherapy while others are treated with nervous system drugs rather than pain killers. 

Differentiating pain also requires an understanding of the location of the pain. A great example of this is abdominal pain. There are many kinds of diseases that cause abdominal pain. Appendicitis and irritable bowel syndrome can both cause gastrointestinal pain in the abdomen. But appendicitis shouldn’t be treated with pain killers. It needs surgery. Equally, irritable bowel syndrome pain is associated with intestinal motility, and drugs that are antispasmodic in nature might be more appropriate than simple pain killers. At the same time, the gastrointestinal tract contains an abundance of cannabinoid receptors, and it’s theorised that endocannabinoid dysfunction is at the root of irritable bowel syndrome.

All of this demonstrates that pain isn’t simply a symptom. It’s an extremely complicated symptom, and this begins to explain why cannabis seems to have so many different, varied effects for different people, different diseases, and different symptoms.

Cannabis for cancer related pain.

There have been a number of studies on cannabis in the treatment of cancer-related pain in adults. In a 2020 study, researchers conducted a retrospective chart review on 232 patients with cancer. They were separated into two groups: cannabis using and non-cannabis using. The researchers found a 23% increase in opioid use in the non-cannabis using group, and improved emotional status in the cannabis-using group, but they found overall improvement in pain to the same degree in both groups.

In another meta-study including 1442 participants, the researchers found that there was no overall statistical significance in pain scores among cannabis users versus placebo.

In a prospective study that studied Nabilone in particular, a synthetic cannabinoid that is usually sold under the name Cesamet, found that pain scores were overall lower in the Nabilone using group versus placebo. As a secondary outcome, researchers found that it also reduced nausea associated with chemotherapy.   

The discrepancies in the research have a lot to do with what kind of cannabis was administered and in what doses and how regularly. These parameters are often inconsistent between studies, and therefore create inconsistencies in results. 

Cannabis and pain in fibromyalgia.

In an Israeli study, 94% of the patients that were studied reported a reduction in pain scores after using cannabis. This is a startlingly different study result than what we observed in cancer-related pain studies. In another study all together, fibromyalgia patients reported improved pain scores, sleep, and mood after cannabis use

The positive interaction between cannabis and pain in the instance of fibromyalgia may be because of the way cannabis exerts anti-inflammatory action. Inflammation is associated with fibromyalgia, and it may be the reduction of inflammation that causes a pain-relieving effect.

Ethan Russo hypothesizes that beneath fibromyalgia is a clinical endocannabinoid deficiency. This might also play a role in why cannabis seems to bring about pain relief when it’s associated with fibromyalgia.

For more information on cannabis and fibromyalgia, check out our blog post about it.

Cannabis in the treatment of irritable bowel syndrome-related pain.

Around 15% of the Canadian population will, at some point in their life, suffer from irritable bowel syndrome. Isn’t that astonishing? The pain of irritable bowel syndrome is related to intestinal motility, or the movement of things through the digestive tract. Some painkillers such as NSAIDs can actually make the symptoms and pain of IBS worse because they are irritating to the lining of the stomach.  

Interestingly, cannabis seems to have a positive effect on the pain associated with irritable bowel syndrome and intestinal motility. As with fibromyalgia, this is hypothesized by Ethan Russo to be related to the prevalence of cannabinoid receptors in the digestive tract. 

IBS is related to fibromyalgia in that many patients with fibromyalgia experience IBS symptoms. This supports the hypothesis that a dysfunctional endocannabinoid system is behind these painful, chronic conditions. 

So while cannabis might not actually reduce nociception, it may reduce the cause of pain by dealing with the underlying problem — at least that seems to be the case with irritable bowel syndrome.

Cannabis and chronic pain; Is cannabis actually a pain killer?

Chronic pain is the number one reason that people seek out medical cannabis. Up to 62% of those who use cannabis use it to manage chronic pain. Chronic pain is associated with a lot of health conditions including the ones we’ve just mentioned. It can also be associated with an injury, with neuropathy, or simply with ageing. 

Researchers have observed the analgesic mechanisms of cannabis to be:

• Inhibition of the release of neurotransmitters and neuropeptides from presynaptic nerve endings
• Modulation of postsynaptic neuron excitability
• Activation of inhibitory pain pathways
• Reduction of neural inflammation  

The exact pathways by which cannabinoids such as THC and CBD do this is unclear. But it offers an explanation as to why for some chronic pain sufferers, cannabis is an effective remedy. As we mentioned, inflammation is sometimes the cause of pain, especially in fibromyalgia. The reduction of neural inflammation can cause a decrease in the chronic pain associated with diseases characterised by neural inflammation.

So yes — cannabis is analgesic, but there are 101 ways that it exerts its analgesic effects. It’s not just that cannabis can decrease pain scores, it also decreases pain unpleasantness. That’s to say — people give less of a damn that they’re in pain.

It’s also worth noting that it often comes up in cannabis studies that using cannabis improves emotional scores and quality of life. We’re not scientifically clear on how these factors connect with physical pain sensation, and how much this plays a role in the analgesic properties of cannabis. Food for thought!

Have you used cannabis to treat pain? What did you use it for and how did it work for you? Let us know your story with cannabis and pain in the comments.