This is Michael Cannon, writing at National Review Online about the Baicker/Finkelstein study summarized below:
[T]he likelihood of screening positive for depression fell from 33 percent to 25 percent, and the share reporting their health to be good or better rose from 55 percent to 68 percent. However, two-thirds of the improvement in self-reported health occurred almost immediately after enrollment, before any increases in medical consumption. The authors posit that much of this improvement could reflect “an improved overall sense of well-being” rather than “changes in objective physical health.”
Supporters of President Obama’s health-care law may tout these benefits, but the [data] does not provide the vindication they seek. First, despite being eligible for Medicaid, 13 percent of the control group had private health insurance — suggesting that on some dimension, Medicaid’s eligibility rules are already too broad.
Second, the [experiment] extended coverage to the most vulnerable population of uninsured Americans, yet the improvements in health and financial security are so far apparently modest. At higher income levels, where individuals have greater baseline access to health insurance and medical care, the benefits of expanding coverage are likely to be smaller and the costs (to the extent that crowd-out is higher at higher income levels) will be greater.