The impact of unrecognized bipolar disorders for patients treated for depression with antidepressants in the fee-for-services California Medicaid (Medi-Cal) program

Background: This study compares hospital use, suicide risk and health care costs of antidepressant patients with recognized bipolar disorders (recognized-BP) and unrecognized bipolar disorders (unrecognized-BP) with non-bipolar (non-BP) patients. Methods: Data from the California Medicaid (Medi-Cal) program were used to identify 25,460 adults with a new episode of antidepressant therapy. Recognized-BP patients received either a bipolar (BP) diagnosis or a mood stabilizer (MS) on or before the initiation of antidepressant therapy. Unrecognized-BP patients received a BP diagnosis or MS therapy after antidepressant initiation. Non-BP patients had no BP diagnosis and no MS use. Multivariate models were used to estimate marginal risks and costs across groups. Results: Recognized-BP and unrecognized-BP represented 14.9% and 6.2% of all antidepressant users, respectively. Less than half of recognized-BP patients used a MS medication in conjunction with their antidepressant. Unrecognized-BP patients were nearly four times more likely to attempt suicide and 50% more likely to be hospitalized than non-BP patients. Recognized-BP patients were at lower risk for attempted suicide and hospitalization relative to unrecognized-BP patients. Unrecognized-BP patients experienced higher 1-year total costs relative to non-BP patients (US$995, p<0.01) and recognized-BP patients (US$682, p<0.05). Limitations: Clinically relevant medical records data were not available making the classification of patients as unrecognized-BP, recognized-BP and non-BP imprecise. Conclusions: Unrecognized-BP is both common and costly. More than half of all recognized-BP patients do not use an MS at the time they initiated antidepressant therapy. More effort is needed to provide early and correct diagnosis and effectively treat both recognized-BP and unrecognized-BP patients.