Use of Marijuana and Other Substances Among Pregnant and Parenting Women With Substance Use Disorders: Changes in Washington State After Marijuana Legalization.

OBJECTIVE: In 2012, possession of marijuana for nonmedical use was legalized in Washington State. This study examined how legalization affected alcohol and drug use in a sample of pregnant and parenting women with substance use disorders.
METHOD: Study participants from nine counties in Washington State (N = 1,359) were questioned about their substance use after completing a 3-year case management intervention program. The sample was divided into two cohorts based on whether participants had completed the program before or after legalization.
RESULTS: Most study participants reported complete abstinence from alcohol and nonprescription drugs at program exit. Among those who were still using substances, women who completed the intervention after marijuana legalization were significantly more likely to report marijuana use at program exit compared with women who completed the intervention before marijuana legalization. Across both cohorts (pre- and post-legalization), we found a positive association of exit marijuana use with alcohol, illegal methadone, other opioids, amphetamines, and cocaine use; even when we controlled for historical period, the association with some of these substances with marijuana use remained evident. Independent of marijuana use, we saw increased use during the post-legalization period of alcohol, illicit methadone, and other opioids.
CONCLUSIONS: Marijuana use at exit from the Parent-Child Assistance Program (PCAP) increased significantly after marijuana legalization in the state. Women who were not abstinent from marijuana at program exit were likely to report use of other substances as well. Our study design demonstrates an association but does not allow us to conclude that marijuana use leads to other substance use among this sample of women with a history of polysubstance use.