General information on cannabis

Last revised: March 18, 2024

Cannabis is a plant that has chemicals called cannabinoids. The most common cannabinoids are THC (tetrahydrocannabinol) and CBD (cannabidiol).

  • THC affects your brain to make you feel “high” and changes how you think, feel and act. The higher the level of THC the greater the intoxicating effects.
  • THC is mostly responsible for the health risks associated with cannabis.
  • CBD does not cause intoxicating effects. CBD is being studied for possible medical uses. The long-term effects of using pure CBD products is unknown.  
  • THC is the psychoactive component in cannabis. It causes cognitive impairment, more commonly known as “the high”.
  • Cannabinoidol (CBD) is non-psychoactive. Research shows that CBD may decrease some of the psychoactive effects of THC.

Cannabis can make you feel happy, relaxed and talkative or it may cause unpleasant effects. These can include confusion, sleepiness, anxiety, fear, panic, paranoia, delusions or hallucinations. The signs of poisoning may include nausea, vomiting, chest pain, dizziness, sleepiness, anxiety, panic attacks and psychosis. If you have had too much or you are not enjoying your experience:

  • Keep calm,
  • Find a safe space,
  • Stay with a friend you trust,
  • Drink water and have something to eat, and
  • Call for help: 9-1-1 or the Ontario Poison Control Centre at 1-800-268-9017.

Most people who use cannabis occasionally will not experience negative health effects over time. The risk for harm is more likely for persons under 25 and persons who use regularly (every day or a few times a week). Not using cannabis is the best way to avoid the risks to your health. If you choose to use, follow these tips to reduce your risk.

Methods of use and types of cannabis products

Cannabis can be inhaled through smoking, vaping, or dabbing, and ingested in foods and drinks.

Dried Flower

Leaves and buds from the cannabis plant can be smoked or vaped. Heating the leaves or buds activates the THC. Learn more about the health effects from smoking cannabis.


Edibles refer to food or drinks that contain active cannabinoids (THC, CBD). The effects of edible cannabis take longer to feel and last longer than smoking or vaping. Learn more lower risk tips.

Cannabis Extracts

Cannabis extracts like hash, kief, wax, or shatter contain a high concentration of THC. High THC products (over 30%) increase the risk of experiencing mental health challenges and dependence. High THC products can change how the brain grows, affecting performance and cognitive function. 


Oils are cannabis extracts that are diluted in a food-grade oil. They can be used to make edibles. 


Cannabis cream is put on the skin. Cannabis cream is usually higher in CBD and lower in THC and is generally used for medical purposes.

Synthetic Cannabis

Synthetic cannabis (K2 and Spice) are illegal products that are stronger and more dangerous than natural cannabis products. Synthetic cannabis can cause seizures, irregular heartbeat, hallucinations and in rare cases, death.

For questions or concerns about a product, or to report adverse reactions, contact the manufacturer. You can also report concerns, complaints or adverse reactions to Health Canada.

Find out more about the different forms of cannabis here.

Using cannabis for medical purposes

Choosing to use cannabis for medical purposes should be done in consultation with a health care provider. The evidence of the effectiveness and safety of cannabis for treating medical conditions is emerging. There are studies that show potential medical benefit for the use of cannabis in some specific cases such as:

  • Nausea and vomiting from chemotherapy,
  • Muscle contractions or stiffness associated with multiple sclerosis,
  • Chronic neuropathic pain, and
  • Drug-resistant pediatric epilepsy, such as Dravet syndrome.
Visit Health Canada for information on Medical use of cannabis  and Consumer information on Cannabis.

For more information on resources and services, visit our Mental Health, Addictions and Substance Use Health Services and Resources webpage.
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