Using inpatient and outpatient service claims associated with the primary ICD-9 code, each claim was classified as being related to mental health conditions, including bipolar disorder (ICD-9 codes 290.00–319.99); or non-mental health conditions (all other ICD-9 codes). To avoid overestimating the number of visits received by children in the cohort we excluded duplicate claims on the same service date and outpatient visits during which only laboratory services were provided (CPT codes 80048 through 89356). However, charges for all services received, including laboratory claims, were included in cost estimates. Mean patient out-of-pocket costs and mean total health costs were estimated among children in the sample. Patient out-of-pocket costs were calculated as the sum of copayments, coinsurance, and deductible payments. Total health costs included both patient out-of-pocket costs and health plan costs (negotiated fees paid to providers for services).
