Biometrics published a study examining the impact of MH/SUD parity in federal employee beneifts on spending and utilization.  The authors found that parity did not dramatically increase spending or service utilization, but suggest that some groups of beneficiaries may benefit more from parity than others.

Neelon, B., et. al.  (2010).  A bayesian two-part latent class model for longitudinal medical expenditure data: assessing the impact of mental health and substance abuse parity.  Biometrics.  

Authors: B. Neelon, A. J. O'Malley, et. al.