Cannabis is a hot topic at the moment. It is completely legal in to use in 11 states in America, and its use for medicinal purposes is permitted in many more. It has become a multi-billion dollar industry, both with people wanting to use it recreationally, and increasingly as an alternative to pharmaceutical medicines.

Cannabis is being touted as being able to help a myriad of medical problems, some of them being Alzheimer’s disease, appetite loss, cancer, Crohn’s disease, eating disorders, epilepsy, glaucoma, mental health conditions, multiple sclerosis, muscle spasms, nausea, and pain[1]. This article will look at the use of cannabis as a painkiller, and examine whether it is a miracle medicine, or snake oil.

What is pain?

Pain is something that we have all experienced. Whilst it isn’t meant to be pleasant, it serves a purpose to alert us that our body is damaged in some way. Pain can be broken down into three types[2]:

  • Somatic pain is the feeling most people associate with pain. It is when a message is sent through the body when it is injured
  • Visceral pain is when tissues or organs become disturbed due to injury or disease. It can feel like it is coming from a different part of the body than the injured area.
  • Neuropathic pain occurs when the nerves themselves are damaged. It does not usually respond well to narcotic painkillers.

How is pain usually treated?

The treatment of pain is something that has been studied by medical science for hundreds of years, and humans have used a wide array of substances to alleviate their discomfort. Stone age tribes would use sacrificial animals and religious offerings, and in Ancient Egypt electric eels from the Nile were used as a basic version of shock therapy (which is actually strikingly similar to some methods practised today)[3].

Nowadays pain is usually treated with drugs, which can all be referred to as analgesics. For light to moderate pain paracetamol and nonsteroidal anti-inflammatory drugs (or NSAIDs) such as aspirin are usually used. Opiates, which are drugs derived from the opium poppy, such as morphine and codeine are used for moderate to severe pain. Synthetic versions of these drugs called opioids are also used, such as fentanyl and oxycodone. Whilst these drugs are incredibly effective painkillers, they are also extremely addictive with side effects such as constipation, nausea, sedation, and respiratory depression[4]. This has led to patients and doctors wishing to explore safer and less risky options.

Gabapentinoids are a relatively new class of drug which include Pregablin and Gabapentin, which are used to treat neuropathic pain. These drugs are not without their risks, which can include disorientation and addiction[5].

How effective is Cannabis as a painkiller?

The main two active chemicals in cannabis are Tetrahydrocannabinol, or THC, and Cannabidiol, or CBD. The key difference between these chemicals is that THC is psychoactive, meaning that it can alter one’s perception of reality, whereas CBD is widely considered to be non-psychoactive. Both are marketed as painkillers, with everything from edible versions such as brownies to topical creams containing one, or both of the ingredients.

There have been hundreds of studies done on the efficacy of the painkilling properties of marijuana, with varying results. Deshpande et All (2015)[6] found that medical marijuana was connected with the improvement of moderate neuropathic pain in adults, although this study recommended that it be used concurrently with analgesics.  Johnson et al (2010)[7] did a study on the effectiveness of cannabis on cancer related pain. Patients were given both THC and CBD, and it was found that the 43% of the patients that were given this drug improved their pain score by 30% or greater. Johnson et all (2013)[8] found that a THC/CBD spray could help to relieve the pain in some cancer patients without them having to increase their other painkilling drugs. Hammell et al (2016)[9] found that topical CBD can provide relief from arthritic inflammation without the risks of psychoactive effects.

There is clear medical evidence that cannabis can be used effectively as a painkiller, although in many studies it is used it as an ancillary drug along with traditional painkillers.

Cannabis is also it is not without its risks. High doses can cause confusion, dry mouth, and intoxication, and its use has also been linked to schizophrenia. Whilst it is clearly having positive results in some patients who are using it, one should be mindful of it being marketed as a miracle drug which is a cure all.


[1] Lava, N. Medical Marijuana FAQ, https://www.webmd.com/a-to-z-guides/medical-marijuana-faq, accessed 4/9/19.

[2] Mack A, Joy J. Marijuana as Medicine? The Science Beyond the Controversy. Washington (DC): National Academies Press (US); 2000. 4, MARIJUANA AND PAIN. Available from: https://www.ncbi.nlm.nih.gov/books/NBK224384/

[3] Dvorsky,G. A Brief History of Painkillers (and Why They Work), https://io9.gizmodo.com/how-drugs-work-to-help-you-ease-the-pain-1452216695, accessed 4/9/19.

[4] Benyamin R et al, 2008, Opioid complications and side effects, Millennium Pain Centre, https://www.ncbi.nlm.nih.gov/pubmed/18443635

[5] Parsons, G (2018), Guide to the management of gabapentinoid misuse, https://www.prescriber.co.uk/article/guide-to-the-management-of-gabapentinoid-misuse/, accessed 4/9/19

[6] Deshpande A, Mailis-Gagnon A, Zoheiry N, Lakha SF. Efficacy and adverse effects of medical marijuana for chronic noncancer pain: Systematic review of randomized controlled trials. Can Fam Physician. 2015;61(8):e372–e381.

[7] Multicenter, Double-Blind, Randomized, Placebo-Controlled, Parallel-Group Study of the Efficacy, Safety, and Tolerability of THC:CBD Extract and THC Extract in Patients with Intractable Cancer-Related Pain, Johnson, Jeremy R. et al., Journal of Pain and Symptom Management, Volume 39, Issue 2, 167 – 179

[8] Johnson, Jeremy R. et al. An Open-Label Extension Study to Investigate the Long-Term Safety and Tolerability of THC/CBD Oromucosal Spray and Oromucosal THC Spray in Patients With Terminal Cancer-Related Pain Refractory to Strong Opioid Analgesics. Journal of Pain and Symptom Management, Volume 46, Issue 2, 207 – 218

[9] Hammell, D C et al. “Transdermal cannabidiol reduces inflammation and pain-related behaviours in a rat model of arthritis.” European journal of pain (London, England) vol. 20,6 (2016): 936-48. doi:10.1002/ejp.818