Stephen Bartels, MD, MS, Susan Horn, Ph.D., Phoebe Sharkey Ph.D.

Purpose: 1) To compare general health service use for medically ill patients in HMOs with and without psychiatric comorbidity controlling for severity of illness and age. 2) To describe the relationship of different managed care cost containment strategies to health service use among medically ill patients with psychiatric comorbidity across six different HMOs Methods: The Managed Care Outcomes Project (MCOP) is a chart study of 12,997 patients in six HMOs with a primary diagnosis of one or more of five medical diagnoses: arthritis, asthma, otitis media, epigastric pain/ulcer, and hypertension. The six HMOs varied with respect to cost-containment strategies including use of specialty psychiatric care, prescribing practices (generic vs. non-generic), physician affiliation (salaried staff vs. contracted), for-profit vs. not-for-profit status, visit co-pay, and mental health carve-out use. Detailed service use were aggregated for one year on medical office visits, emergency and hospital visits, and prescriptions (type, number, and costs). Health service use was compared for medically ill patients without comorbid psychiatric diagnoses to those with psychiatric diagnoses (n=818) and those with a psychiatric chart diagnosis or those receiving treatment with psychiatric medications (n=2851).

Results: Health service use was compared between patients who had a medical diagnosis (only) and patients with a medical diagnosis with psychiatric comorbidity, stratified by index rating of medical severity and age. For young and old patients the presence of psychiatric comorbidity was associated with substantially greater annual outpatient medical visits, medication prescriptions and costs, hospitalizations, and emergency room visits. Differences across the HMOs with different cost-containment characteristics were examined.

Conclusions: Psychiatric comorbidity is associated with dramatically greater use of general health care services. Differences across HMOs suggest further inquiry into the effect of managed care cost-containment strategies on the impact of psychiatric comorbidity on health service use.
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