The American Medical Association has spoken out against the proposed Anthem-Cigna and Aetna-Humana mergers before, but the organization went further in a new analysis on how the consolidation of major insurers could affect competition.

According to the AMA study, the Anthem-Cigna deal would “diminish competition” in 121 metropolitan areas in 14 states, with nine of those 14 already supporting the U.S. Department of Justice’s lawsuit to block the merger on antitrust grounds.

For the Aetna-Humana merger, the AMA said competition would be hurt in 57 metro areas in 15 states. Four of them—Florida, Georgia, Illinois and Ohio—are currently working to block the deal.

“The AMA analyses show that Anthem-Cigna and Aetna-Humana mergers would significantly compromise market competition in the health insurance industry and threaten health care access, quality and affordability,” said AMA President Andrew W. Gurman, MD. “With existing competition in health insurance markets already at alarmingly low levels, federal and state antitrust officials have powerful reasons to block harmful mergers and foster a more competitive marketplace that will operate in patients' best interests.”

The mergers would only exacerbate the existing problems of diminished competition among health insurers. The study said 71 percent of the 388 metro areas studied were already “highly concentrated” and lacked competition. In 40 percent of those areas and 14 states, one insurer had at least a 50 percent share of the market.

“High-quality medical care is only possible if regulators enforce antitrust laws to prohibit harmful health insurance mergers that run counter to patients' best interests,” Gurman said. "It is clear that more can be done in certain states where the attorneys general have not yet taken a strong stance against the mergers.”