Legalization linked to fewer suicides, traffic fatalities, and opioid deaths. A new paper on the public health effects of legalizing marijuana finds “little credible evidence to suggest that [medical marijuana] legalization promotes marijuana use among teenagers” and “convincing evidence that young adults consume less alcohol when medical marijuana is legalized.” And that’s just the start of the positive pot news contained in the paper, which was published this month in the Journal of Economic Literature.
The paper reviews previous research on the public health effects of legal weed, including studies published between 2013 and 2020.
These days, 36 states have legalized medical marijuana and 18 states have legalized recreational marijuana, study authors D. Mark Anderson and Daniel I. Rees note. This has spawned all sorts of concerns about potential public health issues, from promoting the use of marijuana—or other substances—among teenagers to worry about crime, traffic fatalities, and more. But across a range of measures, the evidence is inconclusive at worst and very often quite positive.
For instance: it becomes clear that medical marijuana laws aren’t driving an epidemic of marijuana use among minors. In fact, some researchers have even “found a negative association between [medical marijuana laws] and youth marijuana use.”
Likewise, a 2019 paper found recreational marijuana legalization associated “with an 8 percent decrease in the odds of any marijuana use among high school students and a 9 percent decrease in the odds of frequent marijuana use among high school students.”
Anderson and Rees suggest one possible explanation for the decreased use findings is that “it is more difficult for teenagers to access marijuana when drug dealers are replaced by licensed dispensaries that require proof of age.”
But some small studies have shown a correlation between recreational marijuana legalization and increased teen use. “Researchers will have to wait until more years of post-legalization data become available before drawing firm conclusions about the relationship between [recreational marijuana laws] and youth marijuana use,” the authors say.
The effect of legalization on adult marijuana use is also inconclusive. Using surveys that asked adults about their use, one study found “no evidence of a relationship between [medical marijuana laws] and marijuana consumption among adults,” while another found them associated with a 4–7 percent increase in past-month adult use and recreational legalization linked to a 30 percent increase in use.
Of course, data about the effect of legalization on adult use is complicated by the fact that legalization might make more people comfortable admitting marijuana use in surveys.
Anderson and Rees also say that it’s “difficult to gauge” the effect of marijuana legalization on opioid deaths and on several other public health measures, including mental health, traffic fatalities, workplace health, and crime. Still, there are a lot of positive indicators in the research.
The authors note that “several studies have produced credible evidence” that medical marijuana legalization may reduce the number of opioid-related deaths. However, one 2019 study “confirmed the negative association between legalization and opioid-related mortality…for the period 1999–2010, but found that this association became positive when data for the years 2011–17 were added to the analysis.” The authors suggest that this could be “due to the changing nature of the opioid epidemic. Perhaps marijuana and prescription pain medications are substitutes, but marijuana and heroin are not.”
Recent research on recreational marijuana legalization and opioid deaths has been promising. Another 2019 study found recreational legalization associated with a 14 percent decline in opioid-related deaths, and a 2020 study “found that the legalization of recreational sales was associated with a 16–21 percent decrease in opioid-related mortality.”
In addition, there is “strong evidence that legalizing marijuana discourages the use of alcohol, especially binge drinking.”