Did you know that there are links between cannabis and mental health problems?

Research indicates adolescence is a high-risk period for cannabis use – legalization does not change that.

Cannabis (or weed) is the most widely used non-medical drug in Canada for both adults and youth.  In fact, about 40% of Canadians have used cannabis in their lifetime.  What some people might not realize, however, is that the levels of the active ingredient , THC, have more than doubled in the last twenty years.

Research shows the developing brain’s newly forming structures and connections may be especially vulnerable to disruptions, such as exposure to cannabis, which may increase health and safety risks.

  • 19% of Ontario students in grades 7 – 12 say they’ve used cannabis at least once in the past year.
  • While only 2% of grade 7 and 8 students use cannabis, this figure increases to 37% by grade 12.  1 in 10 users report symptoms of dependence.
  • 9% of teen drivers report driving after using cannabis.

Early use has been connected to higher risk for cannabis use dependence compared to those who start use after brain fully develops in the early-mid 20′s.  Visit, a website geared to teens that explores their use, risks, and concerns about problematic cannabis use.

Frequent use can lead to memory loss and lower IQ.

Frequent (daily) cannabis use that begins in the teen years and continues into adulthood has been linked with declines in memory, intelligence and attention—some of which remain even after the person stops using cannabis.

There’s an alarming connection between cannabis and mental illness.

Links have been made between long-term cannabis use and mental illness. Depression is more common among users (while, at the same time, youth who are depressed are more likely to turn to cannabis, which only worsens the problem with chronic use). The same is true for anxiety disorders.  Refer to Canada’s Lower-Risk Cannabis Use Guidelines (LRCUG) for science-based recommendations to reduce health risks associated with cannabis use at

What’s most alarming, however, is that those who frequently use cannabis during adolescence are significantly more likely to develop psychosis—a severe mental disorder in which thoughts and emotions are so impaired that the person loses touch with reality. Cannabis is also a risk factor for schizophrenia, especially for people who have a family history of the disease.


Did you know that smoking up before driving nearly doubles your risk of a car crash?

Even occasional use can have consequences—especially for drivers.

Incidences of impaired driving while on cannabis are common, with 9% of teenage drivers reporting driving within an hour of smoking cannabis—something which nearly doubles their risk of a crash. Cannabis is also the drug that teens combine most often with drinking alcohol. This can have unpredictable physical and psychological effects (like nausea or panic) and can lead to more risk taking.

Almost 1 in 8 (13%) of Ontario students in grades 7-12 said they used cannabis and alcohol together at least once i the past year.  This is called “cross fading”.  While the effects of co-use may vary among individuals, and less is known about combined use effects than single substance use, there are a number of reasons mixing is not a good idea.

Do you know the risks of using alcohol and cannabis on the same occasion?

Greening Out—Drinking alcohol before consuming cannabis can increase the likelihood of “greening out” which is characterized by feeling nauseous, dizzy, needing to lie down, and possibly vomiting.
Intensified Drug Effects—Highs experienced from each substance can be felt sooner and more intensely when co-used. When drinking occurs first, much higher levels of THC in the blood result.  Alcohol opens the blood vessels in the gastrointestinal tract helping THC to be absorbed more. Intensified negative effects, for some, include increased heart rate, memory impairment, and poor judgement elevating the risk for driving high, getting into a car with an impaired driver, inability to effectively negotiate safe sex, losing personal items, etc.
Overuse —Combined use increases the risk of overusing both substances. The effect of overdoing alcohol—alcohol poisoning—can be deadly. Co-use may lead to drinking beyond one’s usual tolerance, increasing the risk for alcohol poisoning. Cannabis can make it difficult to vomit, which is how the body gets rid of excess alcohol, increasing the risk of choking, or giving way to the effects of alcohol poisoning.

Bottom line, mixing can exaggerate side effects and increase the chance of negative interactions. Avoid drinking and using cannabis on the same occasion is a message both teens and adults need to know.


Students were asked their opinions about it.  The first question – Should cannabis be legal for adults? – had a close three-way tie on how students in grades 7-12 answered this question, although more older students answered “yes”.  The results were:

  • 35% said YES
  • 33% said NO
  • and 32% were unsure.

The second question – When legalized, will you use? – the majority of students said no, but a notable proportion said they would try it, or increase current use.  Given the risks associated with early onset and frequency of use, education to delay initiation or prevent additional use will be important.  The results were:

  • 62% said no
  • 11% said Yes, same as now
  • 8 % said I will try it
  • 4% said Yes, more than now
  • and 14% were unsure.

Understanding why youth start using cannabis can be helpful.  Some say it’s to manage stress as an escape, others use to fit in with a social group because they feel isolated.  Talk to your reen why they think young people use cannabis.  Exploring healthier alternatives to address coping and loneliness is an important strategy to connect with your teen and delay or reduce use.

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