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Hosted by Editor in Chief Lorenzo Norris, MD, Psychcast features mental health care professionals discussing the issues that most affect psychiatry.

Sep 23, 2020

Richard Balon, MD, returns to the Psychcast, this time to conduct a Masterclass on the impact of marijuana use on patients, particularly adolescents.

Dr. Balon is professor of clinical psychiatry and anesthesiology and associate chair of education at Wayne State University in Detroit. He has no disclosures.

Take-home points

  • Marijuana remains a controversial topic as potential legalization looms large in public policy and various groups espouse the positive benefits of marijuana.
  • Current marijuana formulations are more potent than formulations used in previous years. Formulations used today have a higher tetrahydrocannabinol content, with up to 80% THC content achieved through artificial selection.
  • Clinicians are rightly concerned about the well-established negative effects of marijuana on specific populations, particularly adolescents. They also worry about the effect of marijuana on brain development, which could affect educational outcomes, and the significant risk of developing psychosis and/or schizophrenia after using marijuana.
  • Newer research on marijuana use is also suggesting other negative health outcomes, including a potential link between marijuana use and an increased risk of developing various types of cancer.


  • Research over the past 20 years has elucidated the negative effects of marijuana on brain health and development. Marijuana use undermines cognitive function, including executive function and educational outcomes. Longitudinal and twin studies show a decline in the IQ of adolescents who have used marijuana. This is congruent with other established research and public health guidelines urging individuals to avoid the use of psychoactive drugs before the brain finishes maturing at approximately age 25 years.
  • In 2016, Nora D. Volkow, MD, director of the National Institute on Drug Abuse, and other leading investigators in the field published a review of the literature discussing the impact of marijuana cognitive capacity, amotivational syndrome, and the risk of psychosis. Ample evidence based on neuropsychological testing demonstrates a negative impact of marijuana on learning and working memory. Cannabis amotivational syndrome manifests as apathy, reduced concentration, and an inability to follow routines or master new material. Evidence demonstrates that long-term heavy cannabis use is associated with educational underachievement and impaired motivation.
  • Marijuana use is considered a preventable risk factor for the development of psychosis and schizophrenia. Any use of marijuana is estimated to double the risk of schizophrenia, accounting for 8%-14% of cases, and those at greatest risk include adolescents who start at an early age, engage in heavy use, and use high-potency THC.
  • There is limited evidence about the effect of marijuana on PTSD, and a study using a large Veterans Affairs database suggests that marijuana may worsen PTSD symptoms and increase the risk of violence.
  • A well-established physical outcome of heavy cannabis use is cannabis hyperemesis, defined as recurrent nausea, vomiting, and cramping abdominal pain tied to marijuana use.
    • The symptoms may improve temporarily by taking a hot shower or bath.
  • Though more research is required, low-strength evidence suggests that regular marijuana use may be associated with development of testicular germ cell tumors. The association of marijuana use with lung and oral cancer is unclear, partly because marijuana smokers often also smoke cigarettes.
    • Given that we know the smoke in cigarettes is a major risk factor for heart disease, the same concerns must be investigated for individuals who smoke only marijuana.


Fischer B et al. Am J Public Health. 2017 Jul 12;107(8):e1-12.

Volkow ND et al. JAMA Psychiatry. 2016;73(3):292-7.

Lorenzetti V et al. Eur Neuropsychopharmacol. 2020 Jul;36:169-80.

Fried P et al. CMAJ. 2002 Apr 2;166(7):887-91.

Meier MH et al. Addiction. 2017 Jul;113:257-65.

McAlaney J et al. Eur Addict Res. 2020 May 6;1-8.

Ben Amar M, Potvin S. J Psychoactive Drugs. 2007;39:131-42.

Wilkinson ST et al. J Clin Psychiatry. 2015 Sep;76(9):1174-80.

Steenkamp MM et al. Depress Anxiety. 2017 Mar;34(3):207-16.

Chocron Y et al. BMJ. 2019;366:l4336.

Ghasemiesfe M et al. JAMA Netw Open. 2019;2(11):e1916318.

Show notes by Jacqueline Posada, MD, who is associate producer of the Psychcast and consultation-liaison psychiatry fellow with the Inova Fairfax Hospital/George Washington University program in Falls Church, Va. Dr. Posada has no conflicts of interest.

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