A new study finds that oral contraceptives may change a part of a woman's brain. (Photo: Getty Images)

Oral contraceptives — one of the most popular forms of birth control in the U.S. — appear to be changing an important part of the brain, according to a new study presented at the Radiological Society of North America.

In the small study, 50 women — 21 of whom were taking birth control pills — all underwent brain MRIs and had their hypothalamus measured. The hypothalamus is a crucial part of the brain that helps regulate hormone levels and plays a role in several important areas, from your sleep cycle and heart rate to appetite and weight.

The study authors found that women who had been taking birth control pills had a significantly smaller hypothalamus compared to non-pill users.

"We found a dramatic difference in the size of the brain structures between women who were taking oral contraceptives and those who were not," the study author’s Michael L. Lipton, MD, PhD, professor of radiology at the Gruss Magnetic Resonance Research Center at Albert Einstein College of Medicine and medical director of MRI Services at Montefiore Medical Center in New York City, told ScienceDaily. "This initial study shows a strong association and should motivate further investigation into the effects of oral contraceptives on brain structure and their potential impact on brain function."

However, the researchers pointed out that this structural change in the brain did not affect cognitive performance. “They gave women a test of cognitive function and saw no changes in cognition, so that’s very reassuring,” Jonathan Schaffir, an obstetrician-gynecologist at The Ohio State University Wexner Medical Center, tells Yahoo Lifestyle.

Lipton also noted that the preliminary research revealed that pill use was correlated with depressive symptoms. “There have been other studies that also have raised that potential, that the pill can affect mood,” says Schaffir. But it’s not clear whether oral contraceptives are the cause or whether, for example, the reasons why women are taking them, such as painful periods or other medical concerns, might be a contributing factor.

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“It’s hard to draw cause and effect,” Schaffir says. “They’re just associations and don’t necessarily mean the pill is what’s causing it. And it doesn’t mean they should stop taking the pill.”

This isn’t the only study to find that oral contraceptive use may create changes in women’s brains. A February 2019 study published in the journal Frontiers in Neuroscience found that birth control pills may mildly affect a woman’s ability to decipher more hard-to-read emotions on people’s faces, such as contempt or pride. The small study found that women on oral contraceptives were nearly 10 percent worse at recognizing complex emotions while being shown photos of people on a computer screen.

What birth control pill users should take away from the study

Experts are taking this latest study on how pill use may affect the hypothalamus with a grain of salt, saying the results aren’t “game-changing.”

“I don’t think it’s terribly significant,” says Schaffir. He explains that the hypothalamus makes hormones that signal the pituitary gland, telling it when and how much hormone to make. But birth control pills take over part of that job, telling the pituitary gland to make fewer hormones, which helps prevent ovulation. “So it’s not really all that surprising — you’d expect the hypothalamus to be a little less active in that capacity,” he says. “It happens to anything that’s not being used.”

Amit Sachdev, MD, a neurologist and medical director for the department of neurology and ophthalmology at Michigan State University College of Osteopathic Medicine, agrees, telling Yahoo Lifestyle: “While these findings are interesting, I don’t think that they are very meaningful today. The hypothalamus helps to regulate hormone levels. It would not be surprising that when one takes hormones by mouth that the glands that help to produce and control these hormones begin to change. We know this happens with steroids and the adrenal glands. It is not surprising that it would happen with the hypothalamus.”

Sachdev adds: “The important consideration here is that oral contraceptives have been used safely in millions of women for decades. Women have safely transitioned onto and off these medications without ‘withdrawal.’ For this reason I don’t think this study is game-changing.”

So what effect might having a smaller hypothalamus have on women? “Most likely no effect,” Sachde says.

What to do if you’re concerned about using the pill

If you’re taking oral contraceptives, Sachdev recommends asking yourself the following questions: “Are you taking a medication that you need? Do you feel comfortable that you understand the potential risks? While unexpected risks can arise after a medication has already been available for a while, it would be really surprising for new information to become available that completely upended more than 40 years of medical practice,” referring to the fact that the pill has been approved for use since 1960.

Bottom line: “Talk to your provider if you have concerns,” says Schaffir. “But the birth control pill remains a very effective and safe way to prevent pregnancy. I don’t think this study should dissuade anyone from using it as a contraceptive method.”

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