Medicaid Accountable Care Organization Implementation and Behavioral Health Care for Children.

Importance: Medicaid covers almost 40% of US children; state Medicaid programs are increasingly implementing financing and delivery system reforms through Accountable Care Organizations (ACOs). Little is known about how Medicaid ACOs are associated with outcomes for children with behavioral health conditions. Objective: To examine the association between Medicaid ACO implementation and behavioral health care access, unmet mental health needs, and care experience for Medicaid-insured children with behavioral health conditions. Design, Setting, and Participants: This repeated cross-sectional study used data from the 2016-2023 National Survey of Children's Health, a nationally representative household survey of US children. The study included children aged 3 to 17 years insured by Medicaid whose caregivers reported at least 1 current behavioral health condition (anxiety, depression, attention-deficit/hyperactivity disorder, Tourette syndrome, or behavioral problems), with analyses conducted between January 2025 and February 2026. Using a difference-in-differences design, changes in outcomes before and after Medicaid ACO implementation in states that implemented Medicaid ACOs between 2017 and 2022 were compared with contemporaneous changes in states without Medicaid ACO implementation. Exposure: Medicaid ACO implementation. Main Outcomes and Measures: Primary outcomes were (1) having a personal physician or nurse, (2) receiving treatment from a mental health professional in the past 12 months, (3) experiencing unmet mental health needs, (4) receiving effective care coordination, and (5) receiving family-centered care. Results: The sample represented 29 885 590 children (unweighted n = 15 783; females, 41.0%), and 9.1% resided in states with Medicaid ACO implementation. Medicaid ACO implementation was associated with higher reported unmet mental health needs (4.76 percentage points; 95% CI, 0.83-8.70 percentage points). Medicaid ACO implementation was not associated with having a personal physician or nurse, treatment from a mental health professional, care coordination, or family-centered care. Conclusions and Relevance: In this cross-sectional difference-in-differences study of Medicaid-insured children with behavioral health conditions, Medicaid ACO implementation was not associated with broad improvements in children's behavioral health care and was associated with higher unmet needs. These findings suggest that pediatric-specific strategies and workforce investments are needed in Medicaid ACOs to support children with behavioral health conditions.