Medicinal marijuana in psychiatric population: Benefits? Perils?

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Presenting Author(s): Dr. Yakov Shapiro, MD

Co-Author(s): Pierre Flor-Henry

Date and time: 23 Mar 2019 from 14:50 to 15:20

Location: Hawthorn B  Floor Map


  1. To learn about the history of marijuana cultivation and medicinal versus adverse consequences of its use;
  2. To review the impact of cannabis use in psychiatric population, including its association with psychotic states and their distinct neurophysiological signature; and
  3. To become more effective at establishing a dialogue with our patients regarding THC-containing preparations use and its impact on psychiatric care.

Literature References

  1. Arsenault L, Cannon M, Witton J, Murray RM. (2004). Causal association between cannabis and psychosis: Examination of the
    evidence. Brit J Psychiatry.184: 110-117
  2. Batalla A, Bhattacharyya S, Yücel M, Fusar-Poli P, Crippa JA, et al. (2013). Structural and functional imaging studies in chronic
    cannabis users: A systematic review of adolescent and adult findings. PLoS One. 8(2): e55821.
  3. Ben Amar M. (2006). Cannabinoids in medicine: A review of their therapeutic potential. J Ethnopharmacol. 105: 1-25.
  4. Carhart-Harris RL, Leech R, Hellyer PJ, Shanahan M, Feilding A, et al. (2014). The entropic brain: A theory of conscious states
    informed by neuroimaging research with psychedelic drugs. Front Hum Neurosci. 8: 20.
  5. Flor-Henry, P & Shapiro, Y. (2018). Brain changes during cannabis-induced psychosis: Clarifying the marijuana medicine/harm
    dichotomy. J Psychiatry Brain Science, 3(5): 1-13
  6. Flor-Henry P, Shapiro Y, Sombrun C. (2017). Brain changes during a shamanic trance: Altered modes of consciousness, hemispheric
    laterality, and systemic psychobiology. Cogent Psychology. 4: 1-25.
  7. UNODC. World Drug Report (2015). From:
  8. Volkow ND, Baler RD, Compton WM, Weiss SR. (2014). Adverse health effects of marijuana use. N Engl J Med. 370(23): 2219-2227.
  9. Watson SJ, Benson JA Jr, Joy JE. (2000). Marijuana and medicine: Assessing the science base. A summary of the 1999 Institute of
    Medicine report. Arch Gen Psychiatry. 57(6): 547-552.


Marijuana is the most widely consumed recreational drug in the world and its use represents an increasing problem worldwide. A
number of countries have struggled with implementing legislation for its decriminalization and medicinal use. In Canada, marijuana was
legalized in October 2018, and physicians are under increasing pressure to prescribe it for a wide variety of medical and psychiatric
conditions. The use of marijuana-derived products in general and psychiatric populations is increasing, and the prescribing process is
largely unregulated. There are few guidelines for evidence-based use of medicinal marijuana, its potential impact on psychiatric
conditions, or its interactions with psychotropic drugs.

In spite of several medicinal indications, chronic marijuana use is associated with serious consequences including early-onset
psychosis, addiction, increased suicide risk, adverse outcome in mood and anxiety disorders, persistent psychosocial dysfunction, and
neuropsychological abnormalities. This workshop integrates the results of an original spectral electroencephalography (EEG) study and
comprehensive clinical review on the associations between marijuana use and the burden of psychiatric illness. We identify a unique
signature for marijuana-induced psychosis, and provide detailed recommendations for cannabis use in psychiatric population, public
education, and prescribing process of medicinal marijuana use. We believe that the subject of cannabis use in psychiatry is highly
relevant for both psychiatric specialists and mental health workers of all backgrounds.

This workshop is based on the authors’ recent paper: Brain Changes during Cannabis-Induced Psychosis: Clarifying the Marijuana
Medicine/Harm Dichotomy. J Psychiatry Brain Science, 2018, 3(5): 1-13

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