Cannabis, also known as marijuana, weed, pot, and dope, is the most widely used illicit substance in Ontario and Canada. Under the Cannabis Act, as of October 17th 2018, adults 19 years and older in Ontario will be legally permitted to purchase small amounts of cannabis for non-medical use. Learn more about cannabis legalization in Canada.

Cannabis is not a harmless drug and there are risks associated with its use. Short-term effects include:

  • impaired memory and learning
  • impaired coordination and balance
  • effects on mood, feelings and mental health.

Long-term cannabis use is associated with:

  • deficits in memory and attention
  • damage to the respiratory system
  • risk for addiction.

Risks are particularly of concern for those who start using cannabis during early adolescence, as they may experience more severe health effects. For more information on the health effects of cannabis, see the 2018 Canadian Drug Summary on Cannabis Use [PDF] from the Canadian Centre on Substance Use and Addiction.

Lower Risk Cannabis Use Guidelines

If you do choose to use cannabis, follow Canada’s Lower-Risk Cannabis Use Guidelines [PDF]. This is an evidence-based tool developed by the Canadian Research Initiative in Substance Misuse. This tool outlines 10 recommendations when using cannabis such as:

  • delay using cannabis until later in life
  • do not use cannabis and drive
  • limit and reduce how often you use cannabis
  • avoid cannabis use altogether if you are at risk for mental health problems or are pregnant.


It is important to delay cannabis use in youth, as cannabis can affect brain development up until age 25. The Help Your Teem Understand What’s Fact and Fiction about Marijuana [infographic, PDF] can help you start the conversation with your teen about the risks of cannabis.


Like alcohol and other drugs, using cannabis when pregnant or breastfeeding can affect your baby. For more information see Best Start’s Risks of Cannabis on Fertility, Pregnancy, Breastfeeding and Parenting [PDF] report.


Cannabis use impacts attention, coordination, judgment and balance. As a result, cannabis seriously impairs key functions for driving safely. According to recent research, risk for a motor vehicle accident increases up to threefold after cannabis use. There is no research to indicate how long a person should wait to drive after using cannabis.

The Government of Canada recently approved the first oral fluid drug test that will determine if a driver is impaired by drugs. A device is placed in the driver’s mouth to collect a saliva sample that can determine if they have been using drugs. Drug-impaired driving is an offence under the Criminal Code of Canada. Do not drive after cannabis use.

Additional Resources

For Parents, youth and teens:

For Pregnant and Breastfeeding Mothers:

For more information call us at 519.482.3416 or toll free 1.877.837.6143. Ask to speak to a Public Health Nurse.