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 dollars and 1681 dollars less per year in the 6th year relative to UBP patients (p<0.0001 for both estimates). The cost per month increased by 91 dollars for each month of delayed diagnosis (p=0.011). Costs for UBP patients increased by 10 dollars per month prior to their initial BP diagnosis (p<0.001) and by -1.01 dollars 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.