Medical Marijuana: What Psychiatrists Need to Know

Cannabis and Schizophrenia: Trigger or Treatment?
Cannabis and Schizophrenia: Trigger or Treatment?
With growing calls for the use of cannabis in treating psychiatric conditions, psychiatrists need to be aware of the scientific evidence.

TORONTO — Medical marijuana is currently legal in 23 states and the District of Columbia. On a regular basis, studies are released supporting the use of cannabis for the use in the treatment of psychiatric disorders, including post-traumatic stress disorder (PTSD).

Despite the growing calls to expand the use of marijuana for a host of medical conditions, psychiatrists should be hesitant as much of the data out there is inconclusive and marijuana use, even for supposed medicinal purposes, can lead to addiction in some cases, according to Kevin P. Hill, MD, a psychiatrist at McLean Hospital in Belmont, Mass. and an assistant professor at Harvard Medical School.

“It’s an important time to understand what the science is,” Hill told Psychiatry Advisor prior to a presentation on what psychiatrists need to know about medical marijuana at the American Psychiatric Association Annual Meeting. “There’s a gap between what the science is and what the perception is.”

Hill, who is the director of Substance Abuse Consultation Service at McLean, does agree that there is a role for cannabinoids, chemical compounds that act on cannabinoid receptors on cells that repress neurotransmitter release in the brain. However, he is concerned that many people use marijuana for medical purposes even though they may not have a legitimate medical condition.

“One of the key points for medical marijuana is that when you use [it] for conditions where there is little or no evidence and when states put that into law, the policy is ahead of the sciences,” Hill said.

There are currently two FDA-approved cannibinoid pills: dronabinol (Marinol) and nabilone (Cesamet), which are both used for nausea and vomiting associated with chemotherapy as well as to stimulate the appetite of patients with HIV/AIDS. Hill supports the use of the these two drugs, and says there is increasing evidence that it is effective for other condition, including chronic pain, neuropathic pain, and spasticity associated with multiple sclerosis.

Hill contended that synthetic cannibinoids, such as dronabinol and nabilone, might be useful in treating PTSD, but there needs to be more evidence.

He also noted that there may me additional clinical benefit from marijuana as it is known to contain 60 cannibinoids. “Therefore, the plant itself may offer more or different medicinal opportunity than drabinol or nabilone, and we have to open to that idea.”

Indeed, Cambridge, United Kingdom-based GW Pharmaceuticals is investigating a host of cannibinoids for use in many different conditions including epilepsy, type 2 diabetes and ulcerative colitis. It also has a cannibinoid candidate in Phase II for the treatment of schizophrenia. The company also believes than anxiety and depression might be candidates for cannibinoid medicines.

The debate over medical marijuana may also benefit those with mental illness as it may prompt people who otherwise wouldn’t seek treatment to do so, according to Hill.

“If patients call on [their doctor] to go on medical marijuana, I encourage doctors to do a thorough evaluation” before deciding whether to use it on patients, he added.


Hill, KP. Medical Marijuana: What a Psychiatrist Needs to Know. Presentation at: APA 2015. May 16-20, 2015; Toronto, Canada.