Cannabis health effects

The flowers and leaves of the cannabis plant are used for their ability to cause effects on the mind. It's important to keep in mind that cannabis use does have short and long-term health effects.

What are the short-term effects of cannabis use?

Every time cannabis is used it can:

  • Impair your ability to drive safely or operate equipment. Cannabis can slow reaction times, lower your ability to pay attention, and harm coordination.Footnote 1  Using cannabis and driving can result in a car accident, serious injuries or death.
  • Make it harder to learn and remember things. After using cannabis, you may have problems paying attention, remembering or learning things, and making decisions.Footnote 2  Using cannabis can reduce your ability to perform well on the job or at school.
  • Affect mood and feelings. Cannabis use can cause anxiety or panic.Footnote 2 
  • Affect mental health. Cannabis can trigger a psychotic episode (not knowing what is real, experiencing paranoia, having disorganized thoughts, and in some cases having hallucinations).Footnote 2

Learn more about the health effects of cannabis.

What are the long-term effects of cannabis use?

Using cannabis regularly (daily or almost daily) and over a long time (several months or years) can:

  • Hurt the lungs and make it harder to breathe. Cannabis smoke contains many of the same harmful substances as tobacco smoke. Like smoking cigarettes, smoking cannabis can damage your lungs.Footnote 3 
  • Affect mental health. Using cannabis regularly and continuously over time makes you more likely to experience anxiety, depression, psychosis, and schizophrenia.Footnote 4  Higher-strength cannabis products (such as concentrates like “shatter”, wax, dabs) can worsen the mental health effects of cannabis use.Footnote 4  Stopping or reducing cannabis use can improve outcomes.
  • Make you physically dependent or addicted. It is estimated that 1 out of 11 (or 9%) of those who use cannabis in their lifetime will become addicted to cannabis.Footnote 5  This rate increases to 16% for those who start using cannabis during adolescence and up to 1 out of 2 people who smoke cannabis daily.Footnote 5

Learn more about the health effects of cannabis.

How can cannabis affect young people’s health?

Cannabis use that begins early in adolescence, that is frequent and that continues over time is more likely to bring about harms. Some of those harms may never fully go away.

Youth are especially vulnerable to the effects of cannabis, as research shows the brain is not fully developed until around age 25. This is because THC, the substance which gives the “high” in cannabis, affects the same machinery in the brain that directs brain development.Footnote 6  The higher the amount of THC in cannabis, the more likely one is to be harmed by it.

What about using cannabis for medical purposes?

While cannabis is used by some people for their health problems, determining whether cannabis is appropriate to treat your symptoms is best done through a discussion with a health care practitioner.

Health Canada has published information to help Canadians and their physicians make informed decisions about the benefits and risks of using cannabis for medical purposes.

What are the facts about cannabis addiction?

  • Cannabis can be addictive.Footnote 7 
  • Frequent cannabis use that starts in adolescence, increases the chance of addiction.Footnote 5 
  • Close to 1 in 10 adults who have ever used cannabis will develop an addiction to it. This statistic rises to about 1 in 6 for people who started using cannabis as a teenager.Footnote 5 
  • Between 1 in 4 and 1 in 2 of those who smoke cannabis daily will develop an addiction to it.Footnote 5 

Know the signs of cannabis addiction and where to get help.

What are the facts about cannabis impairment?

  • Driving while impaired by cannabis can result in injury or death.Footnote 8 
  • Cannabis can impair the skills needed to drive safely.Footnote 1 
  • The risk of having a car accident is even greater when alcohol is added to the mix.Footnote 4 
  • Using cannabis with other drugs such as certain pain medications or sleeping pills further lowers your ability to concentrate and react quickly to emergencies.Footnote 9 
  • Don’t drive high.
  • How long the impairing effects of cannabis last depends on how it was consumed (smoked, inhaled, ingested) and how much was taken, but effects can last at least six (6) hours or longer after use.Footnote 4

Learn more about impaired driving.