Cannabis (also known as marijuana, pot, weed, grass, ganga etc.), is a substance derived from the hemp plant. It comes in the form of dried plant leaves, hashish (dried resin from plant leaves) or oil (boiled resin). Cannabis can be smoked, vaped, or ingested in the form of food or drink. There are more than 400 chemicals in cannabis. THC is the chemical in cannabis known to be psychoactive. The THC content in Cannabis is far more potent than it was in the past. Higher potency can result in more harmful effects for those who use it.

Cannabis for medical purposes

If you think you need cannabis for medical purposes, please see your health care provider. Cannabis grown for medical purposes can be quite different from recreational cannabis. In addition to having different chemical components, recreational cannabis obtained illegally is not regulated in the same way that medical marijuana is and can contain other dangerous substances such as pesticides, heavy metals and other contaminants. Learn more about accessing cannabis for medical purposes

The effects of cannabis depend on a number of factors such as: how much was used, cannabis potency, how often use occurs, how it was consumed, age and sex, mood and environment, physical and mental health, and use of other substances at the same time (e.g. alcohol).

Side effects of cannabis may include:

  • Slowed motor function
  • Forgetfulness
  • Anxiety
  • Drowsiness
  • Restlessness
  • Poor driving performance

Long-term effects may include:

  • Impaired attention and memory
  • Impaired ability to think and make decisions
  • Respiratory effect such as bronchitis
  • Decreased motivation

Effects on youth:

The brain continues to develop until the age of 25. Because of this, people who use cannabis at a young age are at a higher risk for more long-term effects. 

  • Decreased motivation
  • Attention deficit and hyperactivity
  • Difficulty learning

One out of every six youth who use cannabis during adolescence will develop dependence.

Recommendations to reduce potential negative health effects include not using cannabis.

But, if you choose to use cannabis:

  • Delay cannabis use
  • Know what you’re using and choose lower-risk, less potent (lower THC), cannabis products
  • Don’t use synthetic , or man-made, versions of cannabis (e.g. K2 or Spice)
  • Avoid smoking cannabis – choose something safer like vaporizers or edibles
  • Avoid ‘deep inhalation’ or ‘breath-holding’
  • Limit and reduce how often you use cannabis
  • Don’t use cannabis and drive, or operate other machinery (wait at least 6 hours after using cannabis to drive)
  • Avoid combining risks listed above
  • Don’t use cannabis if you are at risk for mental health problems or are pregnant

 Find out more about the explanations of these guidelines 

Is cannabis addictive?
Yes, cannabis can be addictive. Youth who use cannabis heavily (daily or nearly daily) are at increased risk of dependence; dependence is characterized by psychological and physical symptoms of withdrawal (agitation, irritability, difficulty sleeping, lack of appetite, anxiety, headache, etc.)

Can I drive after using cannabis?
Cannabis use can result in impaired driving. Find out more about impaired driving.

Is cannabis legalized?
The federal government is proposing to legalize cannabis by July 2018. Learn more about the legalization and regulation of cannabis.


Youth resources:

  • Kids Helpline Phone: 1-800-668-6868 - 24 hours a day, seven days a week (Canada only) 
  • The Drug & Alcohol Helpline: 1-800-565-8603