Characteristics of Specialty Mental Health Provider Networks in Oregon Medicaid.

Objective: Provider networks for mental health are narrower than for other medical specialties. Providers' influence on access to care is potentially greater in Medicaid because enrollees are generally limited to contracted providers, without out-of-network options for nonemergency mental health care. The authors used claims-based metrics to examine variation in specialty mental health provider networks.
Methods: In a cross-sectional analysis of 2018 Oregon Medicaid claims data, claims from adults ages 18-64 years (N=100,515) with a psychiatric diagnosis were identified. In-network providers were identified as those associated with any medical claims filed for at least five unique Medicaid beneficiaries enrolled in a health plan (coordinated care organization [CCO]) during the study period. Specialty mental health providers were categorized as prescribers (psychiatrists and mental health nurse practitioners) and nonprescribers (therapists, counselors, clinical nurse specialists, psychologists, and social workers). Measures of network composition, provider-to-population ratio, continuity, and concentration of care were calculated at the CCO level; the correlation between these measures was estimated to describe the degree to which they capture unique dimensions of provider networks.
Results: Across 15 CCOs, the number of prescribing providers per 1,000 patients was relatively stable. CCOs that expanded their networks did so by increasing the number of nonprescribing providers. Moderately negative correlations were found between the nonprescriber provider-to-population ratio and proportions of visits with prescribers as well as with usual provider continuity.
Conclusions: This analysis advances future research and policy applications by offering a more nuanced view of provider network measurement and describing empirical variation across networks.