Topic Overview

What is medical marijuana, and is it legal?

Marijuana is a drug that is made up of the leaves, flowers, and buds of the hemp plant Cannabis sativa. Medical marijuana is the use of this drug to help treat symptoms like pain, nausea, and lack of appetite. It may be used by people who have conditions like cancer, AIDS, or multiple sclerosis.

In Canada, it is against the law to possess, sell, give away, or grow marijuana without legal permission from Health Canada. People who have certain health problems can buy a limited amount of marijuana for their own use, and licensed people can grow and provide medical marijuana to those who need it.

Possession and use of medical marijuana must be authorized by a doctor as a medical treatment.

If you think you might want to try medical marijuana, talk to your doctor. You can also visit the Health Canada website at for more information.

What do the experts say?

The medical use of marijuana has been studied for decades. But experts still don't agree on how safe it is or how well it works.

Some medical experts don't recommend marijuana because:

  • Marijuana may impair your memory, judgment, and coordination. It can increase your risk of being in a car crash.
  • Marijuana smoke may harm your lungs.
  • There are other prescription drugs that may work just as well, such as new kinds of pain and nausea medicines.

Other medical experts do recommend marijuana because:

  • It can provide pain relief when normal pain medicines don't work or have unwanted side effects.
  • It can improve appetite and relieve nausea in people who have cancer or AIDS.
  • It may help relieve symptoms such as pain and muscle stiffness (spasticity) in people who have multiple sclerosis.

Be sure to let your doctor know if you are using medical marijuana. If you're pregnant, it is not safe to use alcohol or drugs, including marijuana.

How do you use medical marijuana?

Medical marijuana should only be used after the usual treatments with normal drugs have been tried. Marijuana interacts with many other medicines. It can be dangerous if taken with medicines that cause sleepiness or control mood, like sedatives, anxiety drugs, and antidepressants. Marijuana lowers blood sugar and blood pressure, so use caution if you take medicines for these conditions. It also increases the chance of bleeding if you are on blood thinners.

Marijuana is usually smoked. It can also be brewed into tea, vaporized, sprayed under the tongue, applied to the skin, or cooked in food.

You may be affected for hours after you use marijuana. How soon you feel the effects of marijuana and how long they last depends on many things, including:

  • How much you used.
  • How you took it.
  • How your own body responds to it.

Unwanted side effects may include:

  • Dry mouth.
  • Red eyes.
  • Anxiety or paranoid thoughts.
  • Faster heart rate.
  • Nausea and vomiting.

Can marijuana produce dependence?

Some people who regularly use marijuana can become dependent on it. This means that they keep using marijuana even though it's having harmful effects on their lives.

The risk of addiction is higher in people who:

  • Start using marijuana when they're young.
  • Use it every day.
  • Have mental health problems.

People who use marijuana often and then quit may have withdrawal symptoms. These include anxiety, trouble sleeping, and intense cravings for the drug.

Are there alternatives to medical marijuana?

Doctors can prescribe two legal alternatives. Both of these drugs contain a form of THC, the main chemical in marijuana.

  • THC and cannabidiol (Sativex). This a combination medicine that can relieve pain in people who have advanced cancer and relieve spasticity in people with multiple sclerosis. This drug has naturally occurring THC.
  • Nabilone (Cesamet). This medicine is used to relieve nausea and vomiting caused by cancer chemotherapy. It may also improve the appetite of people who have AIDS. Nabilone contains man-made THC.

Talk to your doctor if you think these medicines might help relieve your symptoms.

What is synthetic marijuana?

Synthetic marijuana is made of dried plant material that is treated with chemicals that produce effects like marijuana's effects. It is sold as incense under many names, such as K2 or Spice. The labels often claim that these products are "safe" or "natural." But in fact, the active chemicals are created in a lab. And they could be dangerous.

Health Canada does not recommend the use of these products due to the inaccurate ingredient labeling which may lead to serious side effects. Products containing ingredients similar to cannabis are illegal in Canada.

People think that using these drugs will make them feel the same as when they use marijuana. But these drugs are different from marijuana. And the effects are hard to predict. That's because the type and strength of the chemicals used are often unknown. Some people have reported severe symptoms, such as:

  • Fast heart rate and high blood pressure.
  • Vomiting.
  • Feeling agitated or confused.
  • Feeling like others want to harm them (paranoia), or seeing or hearing things that aren't there (hallucinations).


Other Works Consulted

  • Aggarwal SK, et al. (2007). Dosing medical marijuana: Rational guidelines on trial in Washington state. Medscape General Medicine, 9(3): 52. Available online:
  • American Lung Association (2012). Health hazards of smoking marijuana. Available online:
  • Fallik D (2010). As another state approves medical marijuana, neurologists urge caution about prescribing. Neurology Today, 10(4): 1, 5–7.
  • Hill K (2015). Medical marijuana for treatment of chronic pain and other medical and psychiatric problems: A clinical review. JAMA, 313(24). Accessed July 6, 2015.
  • Johnson JR, et al. (2010). 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. Journal of Pain and Symptom Management, 39(2): 167–179.
  • National Cancer Institute (2013). Cannabis and Cannabinoids PDQ – Health Professional Version. Available online:
  • National Institute on Drug Abuse (2011). Marijuana: Facts for Teens (NIH Publication No. 10-4037). Available online:
  • National Institute on Drug Abuse (2012). DrugFacts: Marijuana. Available online:
  • National Institute on Drug Abuse (2012). DrugFacts: Spice (Synthetic Marijuana). Accessed September 30, 2013.
  • National Institute on Drug Abuse (accessed June 2011). Is there a link between marijuana use and mental illness? Research Report Series: Marijuana Abuse. Available online:
  • Thompson A (2015). JAMA patient page: Medical marijuana. JAMA, 313(24). Accessed July 6, 2015.
  • U.S. Department of Justice (2011). DEA Position on Marijuana. Available online:
  • U.S. Food and Drug Administration (2006). Inter-agency advisory regarding claims that smoked marijuana is a medicine. Available online:
  • Whiting P (2015). Cannabinoids for medical use: A systematic review and meta-analysis. JAMA, 313(24): 2456–2473. doi:10.1001/jama.2015.6358. Accessed July 6, 2015.
  • Yadav V, et al. (2014). Summary of evidence-based guideline: Complementary and alternative medicine in multiple sclerosis: Report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology, 82(12): 1083–1092.


Adaptation Date: 7/13/2016

Adapted By: HealthLink BC

Adaptation Reviewed By: HealthLink BC

Adaptation Date: 7/13/2016

Adapted By: HealthLink BC

Adaptation Reviewed By: HealthLink BC