This study assessed the impact of Oregon’s 2007 parity law, which required behavioral health insurance parity, on rates of follow-up care provided within 30 days of psychiatric inpatient care.
Data sources were claims (2005–2008) for 737 individuals with inpatient stays for a mental disorder who were continuously enrolled in insurance plans affected by the parity law (intervention group) or in commercial, self-insured plans that were not affected by the law (control group). A difference-in-difference analysis was used to compare rates of follow-up care before and after the parity law between discharges of individuals in the intervention group and the control group and between discharges of individuals in the intervention group who had or had not met preparity quantitative coverage limits during a coverage year. Estimates of the marginal effects of the parity law were adjusted for gender, discharge diagnosis, relationship to policy holder, and calendar quarter of discharge.
The study included 353 discharges in the intervention group and 535 discharges in the control group. After the parity law, follow-up rates increased by 11% (p=.042) overall and by 20% for discharges of individuals who had met coverage limits (p=.028).
The Oregon parity law was associated with a large increase in the rate of follow-up care, predominantly for discharges of individuals who had met preparity quantitative coverage limits. Given similarities between the law and the 2008 Mental Health Parity and Addiction Equity Act, the results may portend a national effect of more comprehensive parity laws.