Cannabis is a significant political,
health and law-enforcement issue. Across North America, the public discourse on
cannabis tends to focus on sociopolitical and legal issues. With evidence,
opinions and perspectives being released and discussed every day the public has
become increasingly confused about cannabis’ status,
prevalence and effects. For teenagers,
making decisions about cannabis without having a good knowledge of the facts can
have profound consequences.
What are the direct safety risks of cannabis use?
Some people, especially inexperienced users, can experience very unpleasant
events such as intense anxiety, panic and psychotic symptoms when using
cannabis. However the risk of overdose is
extremely low, even among individuals with the highest levels of use.
Perhaps the most significant safety concern for youth is driving under the
influence of cannabis. In student surveys,
approximately 10–20% of student who have a driver’s license, reported driving
within one hour of using cannabis, which is nearly identical to the rates
reported for driving under the influence of
alcohol. Although evidence suggests
that it is not quite as dangerous as driving under the influence of alcohol,
driving under the influence of cannabis is still associated with a significantly
increased risk of collision and injury; that risk increasing further when
driving under the influence of both alcohol and cannabis.
Cannabis intoxication has also been
linked to deficits in attentional focus, information processing, motor
coordination and reaction time.
What are the short- and long-term effects of cannabis use?
Numerous studies indicate that cannabis
use can result in a number of short- and long-term physical, mental, and
psychosocial effects. In studies where strong evidence for a connection with
cannabis use has been found, the following variables were linked to “regular” or
“heavy” cannabis use, which is typically defined as daily or near-daily use :
- When compared to alcohol and
tobacco, among adolescents, cannabis
users have a higher rate of transition to either other drugs or to substance
- The risk of dependence is
approximately 9% among all people who use cannabis, and approximately 16%
among those who started use during adolescence.
- Symptoms of tolerance and
withdrawal, such as
insomnia, anxiety and disturbances
in appetite, are reported, typically in the context of high-frequency,
- Regular cannabis use in adolescence is associated with experiencing
psychotic symptoms, such as
schizophrenia, and also with a possible
increased risk for depression and suicide. Long-term regular use that starts
in adolescence has also been found to be associated with impairments in
attention, memory and verbal learning.
What are the possible consequences of cannabis use during adolescence?
Adolescents are more sensitive than adults to the adverse effects of regular
heavy use of cannabis, including
dependence, poor psychosocial
development, impaired school and work performance, drug-related psychiatric
illness, and generally poorer treatment outcomes.
In some contexts, the long-term cognitive
impairments that result from regular
cannabis use have been reversed, but this
appears less likely for heavy use that begins in adolescence. Youth might be
particularly vulnerable to these negative
outcomes due to the extensive structural and neurochemical changes that are
taking place in the brain during adolescence. In general, the earlier the use of
cannabis started, the more risk there is of long term problems.
As the effects of cannabis can impact
learning and schoolwork completion, youth who use cannabis regularly are more
likely to drop out of high school and, in turn, less likely to pursue
post-secondary education. In addition, youth who are already
vulnerable to poor educational outcomes
due to other factors might be more likely to use cannabis regularly and
affiliate with peers who also use cannabis.
What are the actual limits of the available studies on the effects of cannabis use?
Given the high rates of cannabis use by
youth during this critical period of their development — as well as the
multitude of cannabis-related information being released and discussed every day
— it is more important than ever to review what is known, what is not known and
what evidence is emerging about the effects of cannabis use during adolescence.
Preventive education programs delivered in schools or healthcare facilities are
highly variable in content and execution, but the best ones can delay the
commencement of use by 20–40% compared to the outcome in groups not attending
How is cannabis perceived and used by Canadian youth?
In Canada, use of cannabis is more
prevalent than the use of any other illicit drug, and many start consuming it as
early as late elementary school. About a quarter of youth in age groups 15-19
and 20-24 reported past-year use of cannabis. In total, youth use cannabis at a
rate 2.5 times higher than adults aged 25 and older.
While the current levels of past-year
cannabis use are concerning, more
problematic is the high-frequency use of cannabis reported by some students.
Daily or near-daily use by adolescents is associated with increased harm and the
rates for this type of heavy cannabis use range from 1% to 6%.
In Canada, the youth has a wide range of opinions about
cannabis, some of which are
misconceptions, and conflicting messages received through the media, peers and
adults. They perceive cannabis use to be widespread: it is something that
“everyone” is using “all the time.” They also believe cannabis to be relatively
harmless, viewing it as a more “natural” substance that is not really a drug at
all. Youth have also expressed mixed beliefs about cannabis’ impact on one’s
ability to drive, with some stating that using cannabis improves driving
performance and is not as dangerous as drinking and driving. It is therefore of
paramount importance to provide the best possible information to these young