Legal cannabis access has a complex effect on prescription fill rates for mental health medications, new research shows.

Researchers have long known about the relationship between cannabis use and mental health. But how that practice has affected prescriptions for drugs to treat mental health disorders has been less clear, until now.

A new study from Georgia Tech’s School of Public Policy shows that commercially insured patients living in states with legal cannabis sales filled fewer prescriptions for benzodiazepine-class anti-anxiety drugs, but turned in scripts for antipsychotic and antidepressants at rates higher than residents of states without legal cannabis access.

In one way, the news could be good: benzodiazepines are commonly misused, with sometimes fatal results. But the increase in antipsychotic and antidepressant prescriptions is uncharted territory, says Ashley Bradford, the lead researcher on the study and an assistant professor in the School of Public Policy.

“Does this reflect a social benefit with fewer people feeling anxious, or a social harm with fewer people treating their anxiety effectively and more people experiencing psychosis and depression?” Bradford says.

“We can’t say. What we can say is that physicians and patients seem to be responding to cannabis access in clinically meaningful ways.”

The researchers analyzed prescription data from more than 10 million commercially insured patients and five classes of psychotropic drugs—benzodiazepines, antidepressants, antipsychotics, barbiturates, and sleep medications. They then used a synthetic control method to compare prescription fill rates in states with medical and recreational cannabis laws to those without.

They found that in states where medical cannabis laws were in place, the prescription fill rate for benzodiazepines fell by 12.4% compared to states that did not allow any form of legal marijuana. Legal recreational marijuana caused a bigger drop: 15.2%.

However, in states with medical cannabis laws, the antidepressant prescriptions fill rate increased by 3.8% while fill rates for antipsychotics rose by 2.5%. Recreational cannabis availability resulted in an 8.8% increase in the antidepressant prescription fill rate, according to the study.

The impact of legal cannabis on barbiturates and sleeping medications was insignificant.

“This study suggests that cannabis laws may be significantly associated with the population-level use of prescription drugs to treat mental health disorders, although the associations vary by drug class and state,” the authors write in the paper.

“Our results suggest that additional research is needed to assess whether changes in dispensing of (mental health drugs) are associated with differences in health care outcomes.”

Previous studies focused primarily on the impact of medical and, to a lesser extent, recreational laws on prescription dispensing in the Medicaid and Medicare populations. This work reveals that commercially insured patients seem to respond to legal cannabis access in similar ways to those on Medicare and Medicaid.

The study also demonstrates the impact of different state laws, Bradford says. She says that the results suggest that researchers could identify which aspects of cannabis policies lead to socially optimal outcomes and help policymakers in each state tailor their laws to the outcomes they most care about.

“It’s important to remember that these results don’t tell us anything about the mental health outcomes of people who may be using cannabis instead of anxiety medications, or why prescriptions for these other drugs are increasing,” she says. “So, there’s room for a lot of future research here.”.

The study appears in JAMA Network Open.

Source: Georgia Tech

Original Study DOI: 10.1001/jamanetworkopen.2024.32021