Cannabis (Marijuana)

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. (Source: PROPEL

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

Cannabis & Youth


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.

Youth resources:

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, mood and environment, physical and mental health, and use of other substances at the same time (e.g. alcohol). (Source: CAMH)

Side effects of cannabis may include:

  • Feeling relaxed and happy
  • Increased anxiety or paranoia
  • Increased drowsiness or restlessness
  • Decreased ability to think and make decisions
  • Decreased ability to concentrate and remember
  • Slower reaction time
  • Poor driving performance
  • Increased appetite
  • (Source: Health Canada and CAMH

Long-term effects may include:

  • Impaired attention and memory
  • Impaired ability to think and make decisions
  • Breathing problems such as bronchitis (if cannabis is smoked)
  • Earlier onset of schizophrenia for people at high risk of developing schizophrenia
  • Physical dependence or addiction
  • (Source: CAMH and CCSA)

The Centre for Addiction and Mental Health (CAMH) has developed recommendations to reduce potential negative health effects including 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.)

What are the health effects of cannabis smoke?
There is no safe way to inhale cannabis. Smoke is smoke and it is dangerous to lung health. Cannabis smoke has thousands of chemicals in it and studies have shown that this smoke is similar to tobacco smoke, containing many of the same cancer causing substance and toxic chemicals. Find out more about the effects of second hand cannabis smoke.

What are the effects of cannabis on pregnancy and breastfeeding?
There is no known safe amount of cannabis use in pregnancy and when breastfeeding (source: Best Start). Find out more about cannabis and other drugs during pregnancy.

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

Is cannabis legal?
Not yet. The federal government has announced that cannabis will become legal on October 17, 2018. 

What will be allowed once non-medical (recreational) cannabis is legalized?
Learn more about the legalization and regulation of cannabis.

If cannabis is going to be legal does this mean it is safe?
No, just because something is legal, does not mean it is safe. Cigarettes are an example of a legal substance that is harmful to your health. Learn more about common myths related to cannabis, or check out the facts.

What will be allowed once non-medical (recreational) cannabis is legal?

Once cannabis is legal, individuals in Ontario who are 19 years and older will be allowed to:

  • Possess up to 30 grams of legal dried cannabis or equivalent in non-dried form
  • Share up to 30 grams of legal cannabis with other adults (19 years and older)
  • Buy dried or fresh cannabis and cannabis oil from a provincially licensed retailer
  • Grow up to 4 cannabis plants
  • Make cannabis products, such as food and drinks, at home as long as organic solvents (i.e. dangerous chemicals) are not used

Learn more about Canada and cannabis legalization and Ontario and legalization.

Resources