Mass General researchers find obtaining a medical marijuana card can increase the risk of cannabis use disorder, anxiety and depression

As we all attempt to find our new normal after years of pandemic living, it’s evident that this will involve an immense societal need to focus on individual mental health. With nearly one in five adults living with a mental illness, finding innovative new approaches to diagnosis, treatment, and prevention are crucial to improving the lives of millions of people. Investigators at the Mass General Research Institute are working to do just that. 

Many cannabis dispensaries and websites across the U.S. are promoting the use of marijuana for mental health disorders such as depression and anxiety. However, the scientific research regarding potential benefits of cannabis for mental health disorders is still in its early stages, meaning there is little evidence-based guidance for patients seeking alternative treatments.

In a recent study, Jodi Gilman, Ph.D., the Director of Neuroscience at the Center for Addiction Medicine (CAM) at the Mass General Research Institute as well as an Associate Professor at Harvard Medical School/Massachusetts General Hospital, explored how receiving a card for medical cannabis usage impacts mental health outcomes.

“Oftentimes patients go to a dispensary and get advice from a dispensary worker who usually does not have any medical training,” Gilman explains. “They pick the products that are intriguing to them, and they try things out and they see what they like and what they don’t like.” 

“This is quite different from any other medicine, where you have a formulation that’s well-known and an established treatment/dosage regimen,” Gilman says. “In the current study, we are testing the system of commercialized cannabis that has been set up by Massachusetts.”

In the Mass General Research Institute study, they recruited patients with anxiety, depression, or insomnia that were already interested in using cannabis as a treatment. They also did not advise patients on how much or what kind of cannabis to use, to ensure applicability in a real-world setting. 

In the study, 186 participants with concerns of chronic pain, insomnia or anxiety or depressive symptoms were randomized into two groups. One group immediately received a medical marijuana card and the second was asked to wait 12 weeks before obtaining a card. 

All participants could choose cannabis products from a dispensary, the dose and the frequency of use. 

Compared with the delayed card acquisition group, the immediate card acquisition group had more symptoms of cannabis use disorder, fewer insomnia symptoms and no significant changes in pain severity or anxiety or depressive symptoms. 

“We found that the medical cannabis in the system that we’ve created was not effective for treating pain, depression, or anxiety,” Gilman states. “Some people actually develop cannabis use disorder.”

Cannabis use disorder, or CUD, is characterized by the continued use of cannabis despite significant negative impact on one’s life and health. Clinical research estimates that one in every 10 cannabis consumers will become addicted to the psychoactive drug, developing CUD. 

“We saw the signs of CUD emerge early, and what we found after the 12 weeks is that a substantial minority of patients did develop cannabis use disorder, particularly in the anxiety depression sub-group,” Gilman states. 

This suggests that receiving a medical marijuana card can worsen outcomes for those with anxiety and depression, by adding addiction as a comorbidity. 

“The thing that I want people to know about commercialized cannabis–and particularly people who want to use cannabis for medical conditions–is that we don’t know how much, if any, is safe, or if any is effective for specific medical conditions.” Gilman states. “Chances are, lighter, more infrequent use in older adults is generally safe, but we just don’t know how much and at what potency some people will have adverse responses.”

“The next step for medical cannabis is to get standard formulations and test them in randomized controlled trials. You can make a standard formulation and figure out what dose works and what formulations work for specific medical conditions. This is how we test other medicines.” 

“We have made really important advances on the science of cannabinoids in the past few decades but we have a long way to go. Many mental health conditions are poorly understood, the brain mechanisms underlying these conditions are poorly understood, and established treatments don’t work for everybody. If we could find specific cannabinoids that could be helpful, this would be a huge step forward, but I think more research is needed.”

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