LOS ANGELES — Long after learning that a troubling reading on a screening mammogram was just a false alarm, women continued suffering negative psychological effects, researchers in Denmark have reported.

Six months after hearing they did not have breast cancer, women with these false positives experienced changes in “existential values” and “inner calmness” as great as for women who had cancer. They reported having more anxiety, feeling more pessimistic and having more problems with their sleep and sex lives — as well as other negative outcomes — than women who had normal mammograms.

The effects moderated over time but were still apparent three years after the initial screening.

The findings suggest that health care providers need to pay closer attention to the harmful effects of screening programs, said University of Copenhagen physician-researcher Dr. John Brodersen, lead author of a study detailing the work.

“When I became a doctor and I took the Hippocratic Oath, I said, ‘Do no harm,’” he said. “But this is harm.”

In the U.S., health care policymakers for years have debated the best way to screen asymptomatic women for breast cancer. The hope is that regular mammograms will detect small, early-stage cancers that can be easier to treat.

In 2009, citing concerns about false positives, the U.S. Preventive Services Task Force urged women 50 and older to get a mammogram every two years. Younger women should decide for themselves whether to begin screening, the task force said.

But many medical practices — not to mention groups like the American Cancer Society — still recommend that women get screenings every year, starting at the age of 40.

Early detection is the best way to prevent cancer deaths, screening proponents argue.