At a recent session at the APA Annual Meeting, a panel of psychiatrists addressed many of the common misconceptions around cannabis. With more states legalizing cannabis and changing public perceptions, there is confusion around its safety and uses. At the APA session, Smita Das, M.D., Ph.D., M.P.H., provided an overview of cannabis and its current use. To date, 16 states and the District of Columbia have legalized cannabis for recreational use by adults, and 36 states legalized it for medical use. However, cannabis is still a federal schedule 1 substance (most restricted schedule) under the Controlled Substances Act.

Cannabis is a complex plant with more than 80 chemical compounds, including the mind-altering chemical delta-9-tetrahydrocannibinol (THC), the main psychoactive compound. Cannabidiol (CBD) is another well-studied and commonly available compound. The FDA has approved only one CBD product, a prescription drug that treats a very specific types of seizures. The FDA warns that “some CBD products are being marketed with unproven medical claims and are of unknown quality.”

An estimated 16% of people 16 years and older used marijuana in the last year. Use is higher among teens—one in three high school seniors use marijuana and 6% use it daily, Dr. Das reported. People use marijuana in several different ways, including smoking, eating, drinking, or inhaling it. Much of the teen use is via vaping.

The amount of THC in marijuana has been increasing steadily in recent decades, creating more harmful effects in some people, according to the National Institute on Drug Abuse (NIDA). THC acts on many areas in the brain. In the image below yellow indicates THC impact.

Cannabis has both short and long-term effects on the brain. In the short term, heavy use of marijuana can lead to problems with attention, memory, and learning, according to the Centers for Disease Control and Prevention (CDC). There is evidence that cannabis may exacerbate or hasten the start of psychiatric illness, particularly in young adults. Among people with depression, cannabis use is associated with increased rates of suicidal ideation and attempts. These risks are higher with more potent cannabis and with longer and more frequent use.

Long-term use of marijuana has been linked to temporary hallucinations and paranoia.  Among adolescents, daily use of cannabis is associated with deficits in learning for up to six weeks after stopping and associated with significant decreases in academic achievement.

In a separate panel at the APA meeting Timothy Fong, M.D. with UCLA, reviewed the medical used and benefits of cannabis. Current accepted therapeutic uses include CBD for specific pediatric seizures; THC and CBD to treat muscle spasticity and pain multiple sclerosis (in Canada and Europe); and synthetic THC to treat chemotherapy-induced nausea and to stimulate appetite in people with AIDS.

There is evidence for use of cannabis for chronic pain in adults, however, even with the significant increase in research in recent years, many uncertainties remain. The Centers for Disease Control and Prevention concludes that “cannabis-based products may help treat chronic pain in some adults, but more information is needed… more research is needed to know the specific indications, ideal doses, and how to avoid adverse effects.”

Currently there is no clear evidence for use of cannabis to treat any psychiatric illness, however there is some early research showing potential benefits of pure pharmaceutical CBD for some psychiatric conditions, Dr. Das reported.

Dr. Das also addressed the myth that people don’t become dependent on cannabis. An estimated 9 to 30% of cannabis users become dependent on cannabis and an estimated one in six adolescent cannabis users has cannabis use disorder. People who start using cannabis before age 18 are four to seven times more likely to develop a cannabis use disorder than people who begin as adults, according to NIDA. Withdrawal symptoms can include irritability, changes in appetite, depression, and twitches and shakes.

The panel also addressed treatment of cannabis use disorder. Oscar Bukstein, M.D., M.P.H., with Boston Children’s Hospital and Harvard Medical School, explained the goal of treatment may be either abstinence or reduced use of cannabis (decreased frequency or quantity) and may be directed at improving psychological, work or social functioning.

Bukstein described several types of treatments which have been shown to be effective, including motivational interviewing and several psychosocial interventions, such as cognitive behavioral therapy (CBT), motivational enhancement therapy, and a combination of these. Self-help groups, such as Narcotics Anonymous, can provide important peer support.