Cannabis and cannabinoids for medical purposes

Cannabis comes from the cannabis plant. The main psychoactive ingredient in cannabis is THC (delta-9-tetrahydrocannabinol). THC is a type of cannabinoid. There are many other types of cannabinoids in cannabis. Cannabinoids are chemicals that act on certain receptors on cells in our body, especially cells in the central nervous system.

Some people believe that cannabis can help control or relieve some of the symptoms of cancer or the side effects of cancer treatments. But research studies done so far do not give a clear answer about the effectiveness of smoking cannabis. Research does show that some cannabinoids can help with some symptoms and side effects, and drugs containing cannabinoids have been developed to treat pain, nausea and vomiting.

Medical cannabis

Medical cannabis is legal in Canada, and recreational cannabis is legalized as of October 2018. The Canadian government allows seriously ill people access to cannabis for medical reasons. This is commonly called medical cannabis.

People who want to use cannabis for medical purposes must get a medical document (like a prescription) from a doctor or nurse practitioner. With this document, they can purchase cannabis for medical purposes through licensed producers in Canada. It comes in many forms including dried cannabis, cannabis oil, or fresh cannabis buds or leaves that can be smoked, vaporized, or eaten in food

Health Canada’s Access to Cannabis for Medical Purposes Regulations give people with cancer the option to use cannabis for medical purposes to help manage their symptoms and side effects. Talk to your healthcare team about the benefits and risks of using medical cannabis. They can help you decide if it is right for you.

Find out more about Health Canada’s Access to Cannabis for Medical Purposes Regulations.

Relieving symptoms and side effects

Using cannabis, drugs containing cannabinoids or both may help you relax and give you a sense of well-being. But studies on the effectiveness of cannabis have had different results. Some people with cancer may find using cannabis or drugs that contain cannabinoids helps them cope with these symptoms and side effects.

Nausea and vomiting

Several studies have shown that some cannabinoids can relieve nausea, vomiting or both. These are side effects of some cancer treatments, including chemotherapy and radiation therapy.

Nabilone (Cesamet) is a pill that has synthetic cannabinoids. It is approved in Canada to treat nausea and vomiting caused by chemotherapy. It’s sometimes given to people with cancer if standard antinausea drugs do not help relieve these symptoms.

Find out more about nausea and vomiting.

Loss of appetite

Loss of appetite is a common problem for people with cancer. Loss of appetite and weight loss (which is called cachexia when it is severe) often occur together.

Some people find that cannabis can increase their appetite. Several clinical trials looked at cannabis’s effects on appetite or weight loss in people with cancer. To date, these studies haven’t shown for certain that cannabis can effectively improve appetite. Research into whether or not cannabinoids can help people with cancer deal with loss of appetite hasn’t had clear results.

Find out more about loss of appetite.


Some people claim that cannabis can help relieve long-term (chronic) or severe pain. Research studies done so far do not give a clear answer about the effectiveness of cannabis to relieve pain.

Some clinical trials showed that cannabinoids help reduce pain in some people.

Sativex is a combination of delta-9-THC (Tetranabinex) and cannabidiol (Nabidiolex). It has been approved for use in Canada as a spray that can be applied to the cheek inside the mouth. Savitex may be used to relieve pain from advanced cancer that can’t be relieved with the strongest dose of opioids.

Find out more about pain and opioids.

Side effects and risks of cannabis and cannabinoids for medical purposes

The benefits and risks of cannabis for medical purposes have not been thoroughly reviewed by Health Canada, and individual products have not gone through an approval process. When approving a drug, Health Canada reviews the evidence to make sure that the benefits of the drug outweigh the risks and negative side effects. Talk to your healthcare team if you are thinking about using cannabis for medical purposes or other drugs that contain cannabinoids. There is not enough information to know how using cannabis will interact with drugs and cancer treatments, such as chemotherapy.

Some studies show that smoking cannabis over a long period of time may increase the risk of lung and other cancers. Other studies did not have the same results. Using cannabis may also cause these and other side effects:

  • problems with memory and concentration
  • sensory changes, including a lack of balance and slower reaction times
  • dry mouth
  • rapid heart beat
  • a rise in blood pressure

Ongoing research into cannabis and cannabinoids

Currently, researchers are studying cannabis and drugs that contain cannabinoids to find out more about how they might effectively relieve symptoms of cancer or side effects of cancer treatments. More research is needed to find out the dose and type of cannabis that helps the most with the fewest side effects, the risks and benefits of using medical cannabis for a long time and how medical cannabis might interact with other drugs used to treat cancer.

Researchers are also still trying to find out if cannabis or cannabinoids should be used as medicine to treat certain diseases, including cancer. Research into the effects of cannabinoids on cancer cells in vitro and on experimental animals has shown some promise. But this research is still in the very early stages. Much more study is needed before cannabis or cannabinoids can be used as a cancer treatment.

Expert review and references

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