Women diagnosed with cannabis use disorder during pregnancy were more likely to end up in an emergency room for a psychiatric problem in the year after giving birth, according to a study of more than 2 million California deliveries.
The study was conducted by UC Merced public health Professor Sidra Goldman-Mellor and graduate student LaMecia De Alba, along with researchers from Michigan State University and UCLA. The findings were published in the journal “Annals of Epidemiology.”
It showed that 10 percent of women with cannabis use disorder (CUD) — a medical diagnosis for people who keep using cannabis despite harm to their health, relationships or responsibilities — made a psychiatric emergency visit in their postpartum year, compared to 15.6 percent of women with alcohol use disorder (AUD) and less than 3 percent of women without cannabis or alcohol use disorder.
“One in 10 of the women who were diagnosed with cannabis use disorder during pregnancy went on to have a psychiatric emergency department visit in the postpartum year,” Goldman-Mellor said. “These aren’t just women saying, ‘I feel depressed.’ These are psychiatric symptoms serious enough that they had to go to the emergency room.”
During the six-year study period, CUD among pregnant women increased by 40 percent, whereas the incidence of AUD remained flat.
“It suggests there is a growing population of women who are using cannabis to a problematic extent when they’re pregnant, and that group is at higher risk of serious psychiatric problems,” Goldman-Mellor said.
The study, part of a broader National Institutes of Health grant that looks at substance use, violence victimization and self-harm behavior among pregnant and postpartum women, used hospital delivery records in California to compare psychiatric emergency department visits during the postpartum year among three groups — women diagnosed with CUD, women diagnosed with AUD and a control group without these diagnoses.
The study covers 2016 to 2021, a period that began as California voters approved recreational cannabis use. This legalization has prompted a need for scientific investigation regarding its effects on pregnant populations.
“Just because it’s legal doesn’t necessarily mean that it’s safe,” Goldman-Mellor said. “It’s like alcohol: Many people use it safely, but there’s a subset who become addicted, and that has really negative repercussions for their lives.
“As cannabis becomes more socially accepted, we have to pair that with education about real risks and with systems that actually screen and support pregnant and postpartum women who need help.”
“Some individuals don’t want to take prescribed medications because they know the side effects. With cannabis, there’s not much stated about the actual side effects,” said De Alba, whose research interests center on drug abuse among vulnerable populations. “Some people think that because it’s an herbal remedy, there are no larger side effects.”
Goldman-Mellor emphasized that the study shows a correlation between CUD and psychiatric emergencies but does not establish a cause-and-effect connection.
“This study is not designed to prove that cannabis use disorder causes psychiatric emergencies,” she said. “We didn’t set out to prove causation. What we wanted to show is that pregnant women who are addicted to cannabis are not a neutral group — this is a high‑risk group.”
The findings pinpoint a need for earlier screenings and support, but they leave important questions unanswered.
“There’s still a lot to be learned about the potency or the frequency of cannabis products that are being used within specific populations, especially among pregnant and postpartum women,” De Alba said.
“As cannabis becomes more socially accepted, we need to make sure pregnant and postpartum women are getting the substance use and mental health screening and treatment that they need,” Goldman-Mellor said.
Annals of Epidemiology
10.1016/j.annepidem.2026.110271
Data/statistical analysis
People
Prenatal cannabis use disorder and postpartum psychiatric emergency department visits: A retrospective cohort study of trends and associations in California, 2016–2021
2-Nov-2026
No conflict