States that have legalized recreational marijuana use for adults have also seen a drop in mental health treatment admissions, according to newly published research.
The findings, which came in a study published last month in the journal Health Economics, were based on data from ten states that have legalized adult-use cannabis.
“Recreational marijuana laws (RMLs) continue to grow in popularity, but the effects on mental health treatment are unclear,” wrote Alberto Ortega, a professor at O’Neill School of Public Health at Indiana University and the author of the study.
In the abstract, Ortega said that the study “uses an event-study within a difference-in-differences framework to study the short-run impact of state RMLs on admissions into mental health treatment facilities.”
“The results indicate that shortly after a state adopts an RML, they experience a decrease in the average number of mental health treatment admissions,” Ortega wrote. “The findings are driven by white, Black, and Medicaid-funded admissions and are consistent for both male and female admissions. The results are robust to alternative specifications and sensitivity analysis.”
Ortega said “there is a clear, immediate, statistically significant decrease in total admissions” after a state adopts recreational marijuana laws, and that the “effect becomes more pronounced as time goes on and remains negative through event year four.”
Overall, Ortega estimates that, in the early years following their passage, recreational marijuana laws “led to a roughly 37% decrease in total mental health treatment admissions or about 92 fewer admissions per 10,000 individuals in a state.”
“The results are driven by those under 65, Black, and white individuals. There is also a significant decrease in Medicaid-funded treatment admissions, with a much smaller statistically insignificant effect for non-Medicaid admissions,” he said.
The findings, though compelling, do also present a mystery.
“Due to data limitations, it is difficult to identify the mechanisms leading to the decrease in mental health treatment found above,” Ortega acknowledged. “One possibility is that [recreational marijuana laws] increase marijuana use and that this improves mental health.”
Another possibility, Ortega said, was “that individuals needing mental health treatment can more readily substitute or self-medicate with marijuana, post-[recreational marijuana law].”
Researchers continue to track the effects of marijuana legalization in the United States, a trend that is still in its historical infancy.
A policy paper released last year found that youth marijuana consumption had not seen an increase in states that ended pot prohibition.
In May, a survey found that more than half of marijuana consumers in legal states got their pot from the store.
The findings, which came from a research firm called New Frontier Data, showed that “52% of current consumers say their primary source is a brick-and-mortar dispensary and only 6% say their primary source is a dealer” in states that have legalized adult-use pot.
According to the survey, “43% of [all] current consumers say that a brick-and-mortar dispensary is their primary source of cannabis, compared to 34% in 2022.” Ten percent of current weed consumers said “their primary source is a dealer, down from 13% in 2022,” the survey said.
“Interestingly, 29% of current consumers in illicit markets say that their primary source is also a brick-and-mortar dispensary compared to 17% who say they use dealers. This means that, even in illicit markets, consumers are travelling (sic) across state lines to obtain cannabis from a regulated source, as 42% of consumers say they have sourced cannabis from out of state,” said Dr. Amanda Reiman, the chief knowledge officer at New Frontier Data.