24 Sep 2017

Early Onset Cannabis Use Among Adolescents and Development of Mental Illness

Weed, grass, pot, and dope are among some of the common street names referring to marijuana, the most commonly used illicit drug among Canadian youth, besides alcohol1.  According to the Canadian Alcohol and Drug Use Monitoring Survey 2009, the average age of first time cannabis use among youth was 15.6 years of age. The prevalence of cannabis use for youth (defined in the survey as 15 to 24 years of age) was 26.3%, compared to the adult (25 years of age and older) rate of 7.6%.  Clearly there is a concern here for Canadian youth, and there seems to be a variety of factors as to why young people use cannabis at a higher rate than adults.  Young people are more likely to experiment with cannabis, boys are more likely than girls, single or people without committed relationships are more likely to experiment as well because they are not responsible for anyone else. The younger aged individuals are at the highest risk of cannabis use because they are in the experimental phase as teenagers, where their brains are still developing.  Unfortunately, this age group is also the most susceptible to the long-term consequences of cannabis use. It is important for parents to educate their children on the hazards of marijuana use.  For most adolescents, marijuana is easily accessible and it is perceived as being safe and harmless.  An abundance of evidence is emerging indicating early onset cannabis use among adolescents has negative mental health consequences later on in life.

The immediate positive effects of cannabis makes an individual feel calm, relaxed, talkative and appetite can also be increased (“munchies”).  Negative effects include impaired short-term memory and concentration, loss of interest in activities, distortions of vision, colours and sound.  Cannabis also causes impaired vestibular functions, red eyes, rapid heart rate, and similarly as alcohol, users should not drive or operate dangerous machinery while under the influence of cannabis. In chronic heavy long-term users, potentially mental illness can develop, especially in young adults who have smoked cannabis for years and are vulnerable to mental illnesses. These mental illnesses include depression, schizophrenia, and psychosis characterized by hallucinations and delusions.  When cannabis is inhaled, its effects are felt within seconds.

Withdrawal symptoms include irritability, insomnia, anxiety, weight loss and aggression. However due to the long half-life of cannabis the withdrawal symptoms are not as profound as compared to crack cocaine withdrawal.

Schizophrenia is a mental disorder characterized by psychotic episodes such as hallucinations and delusions.  In schizophrenia there is inappropriate dopamine transmission in the prefrontal cortex.  This is because in schizophrenic individuals there is abnormal prefrontal cortical functioning, which leads to the altered dopamine levels in the prefrontal cortex. Adolescents are at the highest risk of developing psychosis due to cannabis use because their brains are still developing. Family history of mental illness (schizophrenia, psychosis or depression), concomitant substance abuse and child abuse are other factors that can increase risk of developing psychosis in adolescents due to cannabis use. Teenagers are in the experimentation stage with different drugs, and onset of addiction forming habits is most likely to occur with this age group of individuals. This is because during the teenage years the brain is still developing, making circuits and connections, and susceptibility to addictive drugs and behaviours is expected to occur at this stage in development. Adults who have addictive disorders, likely developed the roots of their addiction during the adolescent years when their neurocircuitry was still developing. Early onset drug users are more likely of developing drug related problems such as dependence. In other words, the younger the age of a child when they are first exposed to an illicit substance such as cannabis, the more likely they are of becoming chronic users, and exposing themselves to the long-term hazards of cannabis such as development of psychosis. Impulse control can be impaired in some youth, leading to poor decision making that results in negative outcomes.

In adolescence the prefrontal cortex is still developing and it has not formed all the necessary inhibitory substrates, such as adequate levels of serotonin, to inhibit impulses. This explains why teenagers are more prone to impulsive behaviours, since there are higher levels of impulses or motivational stimuli that cannot be inhibited in teenagers due to low levels of inhibitory substrates such as serotonin. The prefrontal cortex is important in relaying motivational drives to other parts of our brain, but when the prefrontal cortex is not functioning properly it relays motivational drives that are inappropriate and result in bad decision making, and this is what results in poor impulse control.

In order for these negative consequences of marijuana smoking to be prevented, education and family conversion with parents and children needs to be on the forefront.  Unfortunately there is a wide perception by young people that cannabis use is safe and harmless.   This concept needs to be changed in the mind frame of children.  However, this will be a difficult task because of all the positive propaganda of cannabis use everywhere, from celebrities to pro-cannabis internet websites and YouTube.  Even Hollywood movies glorify cannabis use, for example “Harold and Kumar Go to White Castle”, is a movie that is based on two students who constantly smoke weed and go to great lengths just to satisfy their cravings.  Parents need to sit down with their children and have upfront conversions about the dangers of marijuana use for their young children such as development of psychosis. Sometimes children are in a disadvantaged situation in which there is not a stable family household environment.  These youth are probably at a higher risk to experiment and become chronic drug users.  For these specific children there should be more education presented in school and guidance counsellors willing to mentor and help children that seem high risk.  Education should focus on the negative consequences of cannabis use and teach young children the dangers of THC and how to confront people who approach them about using marijuana for their first time.  Education from school and parents should also consist of informing children about positive lifestyle choices instead of succumbing to peer pressures.  Parents should try to keep their teenage children busy in extra-curricular activities in order to prevent them from hanging around individuals that can influence their children in experimenting with drugs.  However, sometimes despite the parents’ best efforts their children do give into the temptations of smoking cannabis.


Written by Komal Kaler,

Pharmacist, Mental health first aid certified



  1. Health Canada. Canadian Alcohol and Drug Use Monitoring Survey.  Available at:  http://www.hc-sc.gc.ca/hc-ps/drugs-drogues/stat/_2009/summary-sommaire-eng.php#cannabis.  Accessed February 28,2011.
  2. Health Canada. Straight facts about drugs and abuse.  Available at: http://www.hc-sc.gc.ca/hc-ps/alt_formats/hecs-sesc/pdf/pubs/adp-apd/straight_facts-faits_mefaits/facts-faits-eng.pdf.  Accessed February 28, 2011
  3. Centre for Addiction and Mental Health. Cannabis.  Available at: http://www.camh.net/about_addiction_mental_health/drug_and_addiction_information/cannabis_dyk.html.  Accessed February 28, 2011
  4. Stahl, Stephen M. Getting Stoned Without Inhaling:  Anandamide Is the Brain`s Natural Marijuana. Clinical Neuroscience Research Center in San Diego and the Department of Psychiatry at the University of California San Diego.  Available at: http://www.psychiatrist.com/pcc/brainstorm/br591101.htm.  Accessed March 3, 2011

5. Howes OD, Kapur S. The dopamine hypothesis of schizophrenia: version III—the final common pathway. Schizophr Bull. 2009 May;35(3):549-62. 6.  The University of Utah, Genetic Science Learning Center.  Mouse Party: Marijuana.  Available at:  http://learn.genetics.utah.edu/content/addiction/drugs/mouse.html.  Accessed March 15, 2011

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