To evaluate temporal changes in pediatric emergency department (ED) visits for mental health problems in Massachusetts based on diagnoses and patient characteristics and to assess trends in all-cause pediatric ED visits.

This statewide population-based retrospective cohort study used the Massachusetts All-Payer Claims Database, which includes almost all Massachusetts residents. The study sample consisted of residents aged <21 years who were enrolled in a health plan between 2013 and 2017. Using multivariate regression, we examined temporal trends in mental health–related and all-cause ED visits in 2013-2017, with person-quarter as the unit of analysis; we also estimated differential trends by sociodemographic and diagnostic subgroups. The outcomes were number of mental health–related (any diagnosis, plus 14 individual diagnoses) and all-cause ED visits/1000 patients/quarter.

Of the 967 590 Massachusetts residents in our study (representing 14.8 million person-quarters), the mean age was 8.1 years, 48% were female, and 57% had Medicaid coverage. For this population, mental health–related (any) and all-cause ED visits decreased from 2013 to 2017 (P < .001). Persons aged 18-21 years experienced the largest declines in mental health–related (63.0% decrease) and all-cause (60.9% decrease) ED visits. Although mental health–related ED visits declined across most diagnostic subgroups, ED visits related to autism spectrum disorder–related and suicide-related diagnoses increased by 108% and 44%, respectively.

Overall rates of pediatric ED visits with mental health diagnoses in Massachusetts declined from 2013 to 2017, although ED visits with autism- and suicide-related diagnoses increased. Massachusetts' policies and care delivery models aimed at pediatric mental health may hold promise, although there are important opportunities for improvement.