Health Care Resource Use, Costs, and Diagnosis Patterns in Patients With Schizophrenia and Bipolar Disorder: Real-world Evidence From US Claims Databases

Abstract Purpose Schizophrenia (SCZ) and bipolar disorder (BD) are typically viewed as nonconcurrent psychiatric disorders, yet patients may experience mood and SCZ symptoms simultaneously. Several studies have shown overlap between SCZ and BD symptoms and susceptibility genes. This study explored the following: (1) patterns of administrative claims; (2) demographic characteristics and comorbidities; (3) health care resource use; and (4) health care costs in patients with diagnoses of SCZ, type I BD (BD-I), and both in a real-world setting. Methods This study was a retrospective cohort trial using 4.5 years (January 1, 2012–June 30, 2016) of Truven MarketScan commercial, Medicaid, and Medicare supplemental databases. We considered a patient to have a new episode of SCZ if he or she had 1 inpatient claim or 2 outpatient claims for SCZ within the identification period (January 1, 2013–June 30, 2015). BD-I was defined in an analogous way. Three study cohorts were defined: (1) SCZ alone (cohort I), met the claims-based diagnostic criteria for SCZ; (2) BD-I alone (cohort II), met the claims-based diagnostic criteria for BD-I; and (3) BD-I and SCZ (cohort III), met the claims-based diagnostic criteria for both SCZ and BD-I. Findings Of the 63,725 patients in the final sample, 11.5% (n = 7336) had a new episode of SCZ alone (cohort I), 80.8% (n = 51,480) had a new episode of BD-I alone (cohort II), and 7.7% (n = 4909) had new episodes of both SCZ and BD-I (cohort III). Considering cohort III, 18.8% (n = 927) received both diagnoses on the same day. In the year after diagnosis, the cohort having a diagnosis of both SCZ and BD-I (cohort III) had the highest all-cause hospitalization rates (67.4% vs 39.5% in SCZ alone and 33.7% in BD-I alone) and the highest mean (SD) number of emergency department visits (3.44 [7.1] vs 1.39 [3.5] in SCZ alone and 1.29 [3.2] in BD-I alone). All-cause total health care costs were highest in the cohort having a diagnosis of both SCZ and BD-I (mean [SD]), $51,085 [$62,759]), followed by the SCZ alone cohort ($34,204 [$52,995]), and the BD-I alone cohort ($26,396 [$48,294]). Implications Our analyses indicate that a substantial number of patients received diagnoses of both SCZ and BD-I, based on claims, in a 2.5-year period. Patients with a diagnosis of both SCZ and BD-I had higher health care utilization and costs than patients with either diagnosis alone. We identified differential patient characteristics, utilization of medications and health care services, and health care costs among the cohorts.