There are limits to mental health coverage and the reason why most employers impose limits is due to cost. Estimates vary widely of how much more mental health coverage costs. Here are some results from some studies:

• A 1998 study sponsored by National Advisory Mental Health Council (NAMHC) and Parity Workgroup, a division of the federal National Institute of Mental Health, estimated that mental health parity would add less than 1 percent to the cost of a health insurance policy for an HMO.

• A 1998 study by Mathematica estimated a 3.6 percent increase across all plans, with a range of 0.6 percent increase for HMOs up to a 5 percent increase for fee-for-service plans.

• A 1997 analysis by the actuarial firm Milliman & Robertson for the National Center for Policy Analysis, examining the cost of a typical mental health mandate (not specific legislation), concluded that mental health parity legislation tends to drive up costs by 5 percent to 10 percent.