Medical marijuana laws are associated with increases in substance use treatment admissions by pregnant women

BACKGROUND AND AIMS: Between 2002 and 2014, past-month marijuana use among pregnant women in the United States increased 62%, nearly twice the growth of the general population. This growth coincides with the proliferation of state medical marijuana laws (MMLs) authorizing physicians to recommend marijuana for approved conditions. We estimated the association between MMLs and substance use treatment utilization among pregnant and non-pregnant women of reproductive age. We also examined whether the association varied across MML provisions, age groups and treatment referral sources to clarify potential pathways. DESIGN: Nation-wide administrative data from the 2002-14 Treatment Episodes Data Set Admissions, and a difference-in-differences design that exploited the staggered implementation of MMLs to compare changes in outcomes before and after implementation between MML and non-MML states. SETTING: Twenty-one MML and 27 non-MML US states. PARTICIPANTS: Pregnant and non-pregnant women aged 12-49 admitted to publicly funded specialty substance use treatment facilities. MEASUREMENTS: The primary outcome variable was the number of treatment admissions per 100 000 women aged 12-49, aggregated at the state-year level (n = 606). Admissions for marijuana, alcohol, cocaine and opioids were considered. The primary independent variable was an indicator of MML implementation in a state. FINDINGS: Among pregnant women, the rate of marijuana treatment admissions increased by 4.69 [95% confidence interval (CI) = 1.32, 8.06] in MML states relative to non-MML states. This growth was accompanied by increases in treatment admissions involving alcohol (β = 3.19; 95% CI = 0.97, 5.410 and cocaine (β = 2.56; 95% CI = 0.34, 4.79), was specific to adults (β = 5.50; 95% CI = 1.52, 9.47) and was largest in states granting legal protection for marijuana dispensaries (β = 6.37; 95% CI = -0.97, 13.70). There was no statistically significant association between MMLs and treatment admissions by non-pregnant women. CONCLUSIONS: Medical marijuana law implementation in US states has been associated with greater substance use treatment utilization by pregnant adult women, especially in states with legally protected dispensaries.