When and how often should you get a mammogram? If you have no special risk factors for breast cancer, the recommendation is every two years. That is if you’re between the ages of 50 and 74.

If you’re in your 40s or older than 74, the answer is a lot more complicated.

Breast Cancer

After months of studying input from healthcare professionals and the public, the U.S. Preventive Services Task Force today released its newest recommendations for breast cancer screenings. The guidelines are not meant for women who are at high risk for the disease.

The panel is made up of independent experts in preventive care and evidence-based medicine. Details are published in Annals of Internal Medicine.

Read More: Why Do We Still Not Know Who Needs a Mammogram? »

Screening for Women in Their 40s

The task force found that mammography screening every two years can be effective for women aged 40 to 49 as well as those between 50 and 74.

However, the panel didn’t go so far as to make that a recommendation. Instead, they advise younger women to consult with their doctors in making that decision.

There’s a smaller benefit and greater potential for negative consequences for women in their 40s, according to the task force.

The major concern is the frequency of false-positive results — those that indicate cancer when there is none. These can lead to more painful tests and potentially risky and unnecessary procedures, as well as a lot of avoidable anxiety.

There’s also potential for serious harm when women are treated aggressively for a type of cancer that wouldn’t have been a threat to their health if left untreated.

“Our findings support a range of choices available to women — from beginning regular mammograms in their 40s, to waiting until age 50 to begin screening, when the likelihood of benefit is greater,” Dr. Kirsten Bibbins-Domingo, Ph.D., the task force vice chair, said in a press release. “Women deserve to understand what the science says about mammography screening, so that they can make the best decision for themselves, in partnership with their doctor.”

Some experts take issue with the guidelines.

“About 25 percent of cases of breast cancer I see in my practice occur in women less than 50,” Dr. Diane Radford, a breast surgical oncologist who will join the Cleveland Clinic next week, said to Healthline. “Thus, I feel we have to be wary about excluding appropriate imaging in that group.”

Radford notes the task force recommendation is different for women depending on their own values, preferences, and health history.

“It is important to note that, as we understand more about the genetics of breast cancer,” she said, “women may be carriers of a low-penetrance gene predisposing to breast cancer [even though they] have no family history of breast cancer.”

Dr. Susan Boolbol is associate professor of surgery at Icahn School of Medicine at Mount Sinai and chief of breast surgery at Mount Sinai Beth Israel.“One of the points that has not been discussed is that early detection also potentially alters treatment that a woman has to undergo for her breast cancer and may also lead to less aggressive treatment,” she told Healthline.

“Over the last several decades, there has been enormous progress in the overall outcome for women with breast cancer,” Boolbol said. “There are many reasons for the fact that 5-year survival for breast cancer is 90 percent, and early detection is one of them.”

Read More: Ultrasounds Effective in Detecting Breast Cancer, but You Still Might Want a Mammogram »

What About Women 75 and Older?

For women 75 and up, the task force makes no recommendation for or against mammography screening. They say more research is needed.

Boolbol thinks the task force erred in not issuing guidelines for women in that age group. She presented an abstract on the topic at the 2015 San Antonio breast cancer symposium.

In the Mount Sinai study she cited, 2,057 patients had screening mammography. Ten were diagnosed with breast cancer. The cancer detection rate in this group was 4.9 per 1,000 screening examinations. According to Boolbol, that’s nearly double the rate the American College of Radiology uses as a standard for when mammograms should be used. 

“We should not base recommendations on an age limit,” she said. “It should really be based on the woman’s expected lifespan and her health status.”

Read More: Early-Stage Breast Cancer Patients Should Think Twice Before Opting for Mastectomy »

What We Don’t Know

Dense breasts can make it harder to detect breast cancer with mammography. The task force said more research is needed to weigh the balance of benefit and harm of screening for women with dense breasts.

Further research may prove 3-D mammography effective in certain women where older technologies fall short.

Then there’s the matter of cost. The panel did not make recommendations regarding what health insurers should or shouldn’t cover. But insurers certainly consider such recommendations when determining coverage.

With that in mind, some experts worry that insurers will eventually stop covering screening mammograms for women in their 40s altogether. Without coverage, some women won’t be able to get a mammogram, even if they want one or a doctor recommends one.

“If, as a result of these recommendations, insurance coverage changes and or fewer women undergo screening mammograms,” said Boolbol, “we will slowly erode all of the progress that we have made in this arena.”