New Study Finds Recreational Marijuana Liberalization Policies Increase Maternal Hospitalizations Involving Marijuana but Have Limited Impact on Newborn Health

RESEARCH TRIANGLE PARK, N.C. — A new study by lead author Angelica Meinhofer, Assistant Professor at Weill Cornell Medicine, along with coauthors at  the University of North Carolina at Wilmington, RTI International’s (RTI), Jesse Hinde, a research economist in RTI’s Community Health Research Division, and Indiana University found that the proportion of maternal hospitalizations with marijuana use disorder increased by 23% (0.3 percentage points) in the first three years after recreational marijuana laws were implemented. The increases were larger in states with legalized commercial sales of marijuana.

The study, forthcoming in the Journal of Health Economics, was released today as a working paper by the National Bureau of Economic Research. Researchers assessed the impact of medical and recreational marijuana laws on maternal and newborn health, an important question for policy makers as marijuana use among pregnant women increased 103% between 2003 and 2017. As of today, 17 states have implemented recreational marijuana laws and 36 states and DC implemented medical marijuana laws.

Researchers also found that in the first three years after the implementation of a recreational marijuana law, the proportion of maternal hospitalization involving a tobacco use disorder diagnosis decreased by 7% (0.4 percentage points), yielding a net zero effect over maternal hospitalizations involving any substance use disorder after recreational marijuana legalization. Recreational marijuana laws were not associated with statistically significant changes in newborn health. Researchers additionally found that medical marijuana law implementation was not associated with statistically significant changes in maternal substance use disorders nor newborn health. The types of newborn health outcomes examined included low birth weight, low gestational age, congenital anomalies, respiratory conditions, feeding problems, neonatal drug withdrawal syndrome, fetal alcohol syndrome and prenatal exposure to noxious substances.

“Our findings implied modest or no adverse effects of marijuana liberalization policies on the array of perinatal health outcomes considered. Importantly, our null findings do not refute evidence that in utero exposure to marijuana can be harmful for newborns,” said Angelica Meinhofer, an Assistant Professor at Weill Cornell Medicine and lead author on the study. “Our findings do suggest that the implementation of the policies is not associated with net changes in newborn health at the population-level that are statistically detectable or economically meaningful in the first three years after adoption. Possible explanations for our null findings of the policies on newborn health may include modest increases in maternal marijuana use disorder along with reductions in tobacco use disorder. Future research must consider additional perinatal health outcomes and subpopulations; long-term effects; and the impact of more recent recreational marijuana laws as states continue to broaden access to cannabis.”

Using birth certificate data from the 2007-2019 National Vital Statistics System in 51 states and hospital discharge data on close to 16 million observations from the 2007-2018 Healthcare Cost and Utilization Project State Inpatient Databases in 34 states, researchers used standard statistical techniques that assess the causal changes in perinatal outcomes between states with and without a policy, before and after the policy was implemented. 

To read the full study, click here.