Diana M. Martinez, MD, conducts a Masterclass on marijuana’s effects on psychiatric disorders.

Dr. 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.

Take-home points

• 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 subjective effects.
• 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 CBD.
• 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 insomnia.

Benefits

• 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 finding.
• 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.

Risks

• 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.

References

National Academies of Sciences, Engineering, and Medicine. Health Effects of Marijuana: An Evidence Review and Research Agenda. Washington, DC: National Academies Press, 2017.

Whiting PF et al. JAMA. 2015;313(24):2456-73.

Fischer B et al. Am J Public Health. 2017 Jul 12. doi: 10.2105/AJPH.2017.303818.

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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 of interest.

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