Nov 19, 2020
Diana M. Martinez, MD, conducts a Masterclass on marijuana’s
effects on psychiatric disorders.
Martinez, a professor of psychiatry at Columbia University, New
York, specializes in addiction research. She disclosed receiving
medication (cannabis) from Tilray for one study and has no other
financial relationships with this company.
- The use of cannabis, recreationally and medically, has been a
controversial topic for ages, and the classification of cannabis as
a schedule I
controlled substance has made it all the more difficult to research
and meaningfully understand its harms and benefits.
- Based on information from the National Academies of Sciences
publication Health Effects of
Marijuana: An Evidence Review and Research Agenda, Dr.
Martinez presents a sweeping overview of the role of cannabis in
two domains: Its ability to worsen psychiatric symptoms, and its
role in causing psychiatric disorders.
- The cannabis plant has 100 cannabinoids. The two most commonly
studied are tetrahydrocannabinol (THC), which creates the "high,"
and cannabidiol (CBD), which does not create a high and has many
- Cannabis is researched and used in several forms, including the
smoked plant or flower form, and prescription cannabinoids based on
THC – namely dronabinol (Marinol), nabilone (Cesamet), and
- Research suggests that both benefits and risks are tied to
using cannabis and cannabinoids.
- Clinicians should have rational discussions with their patients
about the use of cannabis. If patients are no longer responding to
psychiatric treatment, and the clinician wants to talk about their
cannabis use, it is important to understand the common reasons
patients use cannabis, including for chronic pain, anxiety, and
- There is substantial evidence supporting the use of cannabis
and cannabinoids for the treatment of chronic pain. Most studies
evaluated the smoked or vaporized form. Research suggests a dose of
5-20 mg of oral THC is about as effective as 50-120 mg of codeine,
although there are few head-to-head studies to reinforce this
- Cannabis will likely have a role in the pain treatment
armamentarium. The risks of use include intoxication and
development of an addiction.
- Cannabinoids may have a role in achieving abstinence from
addiction to cannabis and other substances.
- THC in the form of cannabinoids shows some promise for its use
in disorders such as PTSD and obsessive-compulsive disorder, but
larger controlled studies are needed. In addition, cannabinoids
have an effect when combined with other behavioral interventions,
such as exposure therapy.
- There is substantial evidence that cannabis has a moderate to
large association with increased risk of developing psychotic
spectrum disorders in a dose-dependent fashion, particularly in
patients who are genetically vulnerable.
- Moderate evidence suggests that cannabis causes increased
symptoms of mania and hypomania in people with bipolar disorder who
use it regularly.
- Cannabis can cause addiction. About 9% of people who use it
will develop a substance use disorder, and the risk of developing a
substance use disorder increases to 17% in people who start using
cannabis in their teenage years. Frequent cannabis use is
associated with withdrawal symptoms, such as irritability, sleep
problems, cravings, decreased appetite, and restlessness.
National Academies of Sciences, Engineering, and Medicine.
Effects of Marijuana: An Evidence Review and Research Agenda.
Washington, DC: National Academies Press, 2017.
Whiting PF et al.
Fischer B et al. Am
J Public Health. 2017 Jul 12. doi:
Show notes by Jacqueline Posada, MD, associate producer of the
Psychcast; assistant clinical professor in the department of
psychiatry and behavioral sciences at George Washington University,
Washington; and staff physician at George Washington Medical
Faculty Associates, also in Washington. Dr. Posada has no conflicts
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