The Treated Prevalence of Bipolar Disorder in a Large Staff-Model HMO

OBJECTIVE: The treated prevalence of bipolar disorder was examined in a large staff-model health maintenance organization (HMO) in western Washington state. METHODS: Automated data for all 294,284 adults enrolled in the HMO or treated by HMO providers were used to determine the number of patients treated for bipolar disorder between July 1, 1995, and June 30, 1996. Patients with bipolar disorder were identified using computerized records of inpatient diagnoses, outpatient visit diagnoses, and outpatient prescriptions of mood stabilizers. Validity of the identification procedure was confirmed by review of a random sample of outpatient records. RESULTS: The treated prevalence of bipolar disorder in the HMO was .42 percent. Somewhat higher treated-prevalence rates were found for women, younger enrollees, family members of HMO subscribers, enrollees in some of the individual plans within the HMO, and enrollees in the state's Basic Health Plan program for low-income residents. Of the 1,236 adults treated for bipolar disorder, 93 percent made at least one visit to specialty mental health services, and 86 percent received mood-stabilizing medications. Only a small percentage of the 1,236 patients received treatment with an antidepressant, an antipsychotic, or a benzodiazepine without having a mood stabilizer prescribed. CONCLUSIONS: The treated-prevalence rate found in this HMO population is higher than rates previously reported for prepaid health plans and lower than estimates from large population surveys. The majority of treated patients received specialty mental health services and treatment with mood-stabilizing medications.