ACO = accountable care organization; CMS = Centers for Medicare and Medicaid Services; Med-Peds = Medicine-Pediatrics; NA = not applicable; OB-GYN = obstetrics-gynecology.

↵^aOwnership structures: independent practices do not have any ownership relationships beyond the practice itself. Systems include medical group practices owned by an organization that owns other practices but no hospital, simple system practices owned by an organization that owns other practices and ≥1 hospital, and complex system practices owned by an organization that itself owns a medical group or another system (ie, a system within a system).

↵^bDenotes independent variables included in models estimating adjusted predictors of difficulty obtaining care for children with behavioral health disorders (see Table 2). These comprise pre-determined independent variables (and model specifications) that were based on our hypotheses regarding practice ownership structure, Medicaid ACO participation, and a parsimonious set of controls in these descriptive cross-sectional models. Other practice attributes in Table 1 are offered for descriptive context only.

↵^cDesign-based Wald c for categorical variables; F-statistic for continuous variables.

↵^dOther clinicians could be any of the following: physician assistants, nurse practitioners, clinical nurse specialists, clinical social workers, counselors, marriage and family therapists, or psychologists but were most frequently physician assistants or nurse practitioners with further specification about the role they might be playing clinically.

↵^eIncludes pediatric specialists who also prescribe psychotropic medications (eg, developmental-behavioral pediatricians, pediatric neurologists, neurodevelopmental pediatricians).

↵^fVia CMS Comprehensive Primary Care Plus participation lists. Note that these practices overlap with practices reporting participation in primary care improvement programs.

↵^gInstead of controlling for census region in models used to obtain adjusted estimates, we controlled for state in which the practice is located.