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Effects of Chronic Marijuana Use in Adolescence

The unifying chant “free the weed” was heard recently in the Toronto downtown core for the annual Global Marijuana March (Yuen, 2016). Rally attendees sought to push the liberal government to accelerate their promise to legalize marijuana. Political debates and legalization is ongoing, one prominent reason for prolonged legislation is the adverse effects of early chronic use of the drug. Researchers posit that early chronic use worsens cognitive performance and increases likelihood of mental illness later on in life (Jacobus, Squeglia, Infante, Castro, Brumback, Meruelo, & Tapert, 2015; Casadio, Fernandes, Murray& Di Forti, 2011).
Jacobus et al. (2015) examined networks in the brain of marijuana using adolescents compared to healthy controls to determine any differences. They found that exposure to marijuana may affect multiple brain networks involved in widespread cognitive, emotional, and motor functions. Particularly, their results showed an imbalance in cognitive control associated with attention and executive function as well as impulsivity.

Another recent study examined the impact on physical and mental health on a group of 506 young men from the age of 14 to 26 (Bechtold et al., 2015). Participants of this study were part of a larger Pittsburgh Youth Study in the United States to examine delinquency, substance abuse, and mental illness. A distinguishing factor of this study among the many other studies pertaining to young people and marijuana intake was that researchers examined participants across ethnicity and had frequent check-ins with participants over a long duration of time.  This study, unlike the previously delineated study, found that chronic marijuana users were not more likely than others to experience physical or mental health problems in their mid-30s.  Despite these findings, Bechtold et al. (2015) caution one to consider the potential effects on many other domains such as cognitive and intellectual functioning, alterations in brain function and structure, academic and occupational failure and psychosocial adjustment.






Overall, the results of these studies show that exposure to marijuana can result in attention and executive function difficulties in adolescents; however, its use does not increase the likelihood of having a mental illness.  Furthermore, the results do not indicate whether the cognitive affects found in adolescent marijuana use is lasting.

At Simone Friedman SLS, our Speech Therapists treat executive function and attention difficulties regardless of the cause.  We often get parents who bring in their children ages 12-26 complaining that their children have difficulty:

  • paying attention in class
  • breaking down assignments into manageable parts
  • getting organized
  • problem-solving
  • planning long term for their future careers.
  • managing their time
  • prioritizing
  • Insight and Self-Awareness

Regardless of the etiology of executive dysfunction, be it due to marijuana use and/or struggles one see’s with normally developing teenage brains, executive dysfunction is a common complaint that we hear, assess and treat.  Our Speech Therapist’s at Simone Friedman SLS begin by working with the individual and educating them on the brain and the necessary executive function skills required to be successful in life.    We then assess specific areas of weakness and work with the individual on finding the best strategies that they can use in the context of their everyday lives (school, home, personal relationships) in order to improve function.



Bechtold, J., Simpson, T., White, H. R., & Pardini, D. (2015). Chronic adolescent marijuana use

as a risk factor for physical and mental health problems in young adult men. Psychology of Addictive Behaviors, 29(3), 552.

Casadio, P., Fernandes, C., Murray, R. M., & Di Forti, M. (2011). Cannabis use in young people:

The risk for schizophrenia. Neuroscience and Biobehavioral Reviews, 35, 1779 –1787. .neubiorev.2011.04.007

Jacobus, J., Squeglia, L. M., Infante, M. A., Castro, N., Brumback, T., Meruelo, A. D., & Tapert,

  1. F. (2015). Neuropsychological performance in adolescent marijuana users with co-ocurring alcohol use: A three-year longitudinal study.

Yuen, J. (2016, May 7). Marchers want government to ‘free the weed.’ Toronto Sun. Retrieved


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