The impact of unrecognized bipolar disorders among patients treated for depression with antidepressants in the fee-for-services California Medicaid (Medi-Cal) program: A 6-year retrospective analysis

Introduction: The cost of unrecognized bipolar disorders over time is unknown. Methods: Ten years of data from the California Medicaid program were used to identify depressed patients initiating new episodes of antidepressant therapy and with 6+ years of post-treatment data. Recognized bipolar (RBP) patients received a BP diagnosis or used mood stabilizers in the pre-index period. Unrecognized bipolar (UBP) patients received an initial BP diagnosis or used a mood stabilizer in the post-index period. Depression-only (MDD) patients had no BP diagnosis or mood stabilizer use. Three analyses were conducted: (1) regression models of cost per year, (2) a regression model of aggregate cost over 6 years and (3) a time trend analysis of the costs for UBP patients. Results: 14,809 patients were identified: RBP 14.5%, UBP 28.2% and MDD 57.3%. The growth in costs per month for UBP patients over 6 years (171%) far exceeds the growth for RBP and MDD patients (82% and 95%, respectively). RBP and MDD patients cost $2316 and $1681 less per year in the 6th year relative to UBP patients (p < 0.0001 for both estimates). The cost per month increased by $91 for each month of delayed diagnosis (p = 0.011). Costs for UBP patients increased by $10 per month prior to their initial BP diagnosis (p < 0.001) and by - $1.01 thereafter (p = 0.006 for the change in slope). Limitations: Classification of patients based on diagnosis or mood stabilizer use using paid claims data is inexact. Conclusions: Early diagnosis of bipolar disorders may significantly reduce health care cost.