A federal law that requires group health plans and health insurers offering mental health benefits to make the aggregate annual or lifetime limits on mental health benefits no more restrictive than the limits on medical and surgical benefits. The MHPA covers group health plans for plan years beginning on or after January 1998, and gives employers discretion regarding the extent and scope of mental health benefits provided. The MHPA, which does not apply to benefits for substance abuse or chemical dependency, was substantially expanded by the Mental Health Parity and Addiction Equity Act of 2008 (MHPAEA).

The MHPA exempts small employers, defined as employers that:

The definition of small employer is different under the MHPAEA, for plan years beginning after October 3, 2009.