Medical marijuana may increase rates of cannabis use disorder, study finds

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A new study by Massachusetts General Hospital (MGH) found patients given medical marijuana cards were more likely to develop cannabis use disorder (CUD). In addition, patients using medical marijuana reported no significant improvements in pain, anxiety, or depressive symptoms.

The study, published in JAMA Network, was led by Jodi Gilman, PhD, of the Center for Addition at MGH. The study aimed to discover the effect that medical marijuana cards have on the rate of CUD among patients as well as their symptoms of chronic pain, insomnia, anxiety, or depression. To do so, Gilman and her team of researchers conducted a random clinical trial in the Greater Boston area from July 1, 2017, to July 31, 2020. There were 186 participants ranging from age 18 to 65 years old, all with symptoms of either pain, insomnia, or anxiety, or depression. Participants were randomized into two groups. One group was giving a medical marijuana card immediately and the other was asked to wait 12 weeks. The groups were then categorized by symptoms, age, and sex.

The study’s results showed that those immediately given the medical marijuana card were more likely to develop CUD. In addition, the immediate acquisition group reported fewer signs of insomnia, however, they reported no significant improvements in symptoms of pain, anxiety, or depression. The study found rates of CUD were particularly high among those with anxiety and depression.

"Our study underscores the need for better decision-making about whether to begin to use cannabis for specific medical complaints, particularly mood and anxiety disorders, which are associated with an increased risk of cannabis use disorder," Gilman said in a statement. "There needs to be better guidance to patients around a system that currently allows them to choose their own products, decide their own dosing, and often receive no professional follow-up care."

Researchers said future studies should focus on the benefits of medical marijuana on insomnia and the effect it has on CUD specifically in those with anxiety and depression.