Health & Cannabis

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Cannabis plant contains chemicals with psychoactive and therapeutic properties. The chemical used therapeutically in medical cannabis products is Cannabidiol (CBD). The chemical responsible for the psychoactive properties, which affect the brain (mind-altering), is the Tetrahydrocannabinol (THC). Cannabis products include the dried herb as well as hashish and hashish oil. Cannabis is also known by other names such as marijuana, weed and pot.

Cannabis for non-medical use is legal in Canada as of October 17, 2018. Under the new laws in Ontario, adults 19 years of age or older are able to:

  • Purchase cannabis through a provincially authorized retailer
  • Possess up to 30 grams of dried legal cannabis in public
  • Share cannabis with people 19 years of age or older

Criminal offences for sharing/selling cannabis with/to minors are included in the new legislation as well as penalties for individuals who engage youth in cannabis-related offences.

Drug-impaired driving remains illegal in Canada. Law enforcement can currently detect drug-impaired driving using Standard Field Sobriety Testing and Drug Recognition Expert evaluation. Roadside Drug Screening Equipment has also been approved for use by law enforcement.

It remains illegal for travellers to take cannabis out of Canada or to bring it back from other countries.

The rules and regulations related to cannabis may be different in other provinces and territories.

The law on cannabis use for medical purposes is different and can be found at Health Canada.

Research shows that cannabis can be harmful to health if consumed frequently and to those who start using cannabis at a young age.

  • Cannabis impairs the mental ability to drive or use machinery safely for up to six hours or longer after use.
  • Frequent and heavy cannabis use can have significant effects on:
    • mental health (especially if there is a family history of mental illness)
    • adolescent brain development
    • cognitive (e.g. memory, attention span) and psychomotor functioning (e.g. motor coordination, and operative tasks)
  • Similar to tobacco smoke, cannabis smoke contains cancer-causing chemicals and other harmful by-products
  • Long-term, chronic cannabis smoking is linked to poor respiratory health, including:
    • increased coughing and wheezing
    • bronchitis
    • lung and laryngeal cancer

The only way to completely avoid the health harms associated with cannabis is to not consume cannabis. The potential health harms can be reduced by:

  • avoiding cannabis consumption during adolescence
  • limiting how often you consume and avoiding high-potency cannabis
  • not combining tobacco or alcohol with cannabis
  • consuming only small amounts of cannabis edibles and then waiting to feel the psychoactive effects, which may take up to two hours

Using a vaporizer is less harmful than smoking and it does not expose others to second-hand smoke. Smoking anything, including tobacco and/or cannabis is harmful to lungs.

Pregnant individuals and individuals with personal/family history of psychosis should avoid cannabis use.


Related information:

Canada’s Lower-Risk Cannabis Use Guidelines

Legal Access to Non-Medical Cannabis: Approaches to Protect Health and Minimize Harms of Use

Drug-impaired driving is illegal in Canada. Law enforcement have the ability to detect drug-impaired driving using Standard Field Sobriety Testing and Drug Recognition Expert evaluation.


If using cannabis, avoid driving for at least six hours after use, or more if needed.

Cannabis has been found to negatively affect the cognitive and psychomotor skills needed for driving including memory, attention, and stop reaction time. This can significantly impact your ability to drive safely. Driving under the influence of both alcohol and cannabis causes greater impairment.

It is illegal for youth under the age of 19 to buy, sell or possess cannabis products.


The legal age limit for buying and consuming cannabis has been set at 19 years of age in Ontario. Early and frequent cannabis use during adolescence has been linked to a higher and longer-lasting health outcomes, including:

  • problems with memory and learning
  • having trouble thinking and problem solving
  • higher risk of developing psychosis which is a mental state in which you lose touch with reality

The potential risks associated with frequent cannabis use are higher during adolescence and up to age 25 while the brain continues to develop.

Youth who have supportive parents, teachers, and other adults in their lives are less likely to use alcohol and other drugs, including cannabis. When supportive adults create opportunities to talk about cannabis, it in itself is a protective factor against developing substance use issues.


Resources to help you talk to youth about cannabis:

Cannabis Talk Kit: Know how to talk with your teen

Parent Action on Drugs 

Kids Help Phone 

There are no safe limits of cannabis use during pregnancy. Pregnant individuals should avoid cannabis use and exposure to second-hand cannabis smoke. Cannabis use during pregnancy may increase the risk of having a low birth weight baby, small for gestational age baby and preterm birth.

Individuals who are breastfeeding or planning to become pregnant should avoid using cannabis and exposure to second-hand cannabis smoke.



Pregnancy to Parenting Blog: Is marijuana use safe when pregnant or planning a pregnancy?

Risks of Cannabis on Fertility, Pregnancy, Breastfeeding and Parenting 

Are you pregnant or considering pregnancy?