Bloomington, IN: The enactment of statewide adult-use marijuana legalization laws is associated with a decline in overall mental health treatment admissions, according to data published in the journal Health Economics.

A researcher affiliated with Indiana University’s O’Neill School of Public Health tracked trends in mental health admissions in ten states following legalization. He concluded that the adoption of adult-use legalization “led to a roughly 37 percent decrease in total mental health treatment admissions or about 92 fewer admissions per 10,000 individuals in a state.” He also identified “a significant decrease in Medicaid-funded treatment admissions.”

He concluded: “Once a state has an RML [recreational marijuana law], there is a clear, immediate, statistically significant decrease in total admissions. The effect becomes more pronounced as time goes on.”

The study’s author did not identify a specific reason for this trend, but he did suggest: “One possibility is that RMLs increase marijuana use and that this improves mental health. … There is also the possibility that individuals needing mental health treatment can more readily substitute or self-medicate with marijuana, post-RML.”

Survey data confirms that cannabis consumers frequently use the substance to improve anxiety and depression, although data is inconsistent with respect to its efficacy in treating mental health conditions.

Full text of the study, “The highs and lows: Recreational marijuana laws and mental health treatment,” appears in Health Economics