Ed Cara | 12/4/2019 1:25pm

Scientists this week say they’ve found preliminary evidence that women who use birth control pills have differences in their brain structure compared to women who don’t. But it’s still too way early to know whether these differences are genuine or could have a meaningful impact on someone’s health.

The study’s authors enlisted the help of 50 healthy women, half of whom had reported using birth control pills. They scanned their brains using MRI, focusing on a small region called the hypothalamus.

The hypothalamus helps control the release of many hormones and is located right next to the pituitary gland at the base of the brain. These include the key hormones that regulate a woman’s fertility and menstrual cycle, estrogen and

progesterone. When a woman takes hormonal birth control, they’re actually taking the synthetic versions of these hormones in some combination, which stops the cycle in its tracks.

But according to study author Michael Lipton, a neuroscientist and director of radiology research at the Albert Einstein College of Medicine in New York, there’s never been any serious exploration of whether the use of these hormonal contraceptives could affect the hypothalamus.

When Lipton and his team looked at the brain scans of both groups, they found a clear contrast. Women on birth control, on average, had a smaller hypothalamus than those not on birth control. Moreover, there was also a link between a smaller hypothalamus and women experiencing more symptoms of depression and anger. “The finding is a first ever and does need to be replicated,” Lipton told Gizmodo via email. “It is nonetheless not marginal and unlikely to be due to chance variation.”

It’s important to point out that these findings are not yet peer-reviewed. They’re being presented in an early preview this week at the annual conference of the Radiological Society of North America (RSNA). While plenty of studies presented at conferences go on to become wholly accepted research, it does mean that other scientists haven’t had the chance to examine the team’s raw data or critique their interpretation of it in an open and transparent fashion.

But the team’s findings certainly aren’t implausible, according to Alexandra Herrera, a research assistant professor of gerontology at the University of Southern California who has studied how changing levels in sex hormones over a woman’s life—as well as the use of birth control—are linked to changes in their mood and health, including differences in the brain.

“Other work in women has shown similar associations, with gray matter volume differing between women using hormonal contraceptives and women not using hormonal contraceptives,” Herrera, who is not affiliated with the study, told Gizmodo via email. In these studies, women on birth control tended to have more gray matter in the areas that were examined. But “finding structural differences in additional brain regions is not unexpected,” she said.

At this point, it’s still anyone’s guess as to how birth control could be shrinking the hypothalamus. But Lipton notes that progesterone is thought to promote brain growth. If hormonal contraceptives are interfering with the typical release of progesterone, “that could lead to loss of volume, especially over the longer term,” he speculated.

Herrera and Lipton are both careful to add that these sorts of studies can only show a correlation between birth control and brain differences, not a causation. To know whether these differences were caused by birth control use for sure, you’d have to study the brains of women before they’ve ever taken birth control, then randomize if they’ll take it or not, and finally study them after.

Even if birth control could be causing real changes in the brain, it’s still unclear whether these changes are significant enough to affect a person’s life, much less in a negative way. Some research has pointed to a link between birth control use and things like emotion regulation or how women feel about a potential suitor’s attractiveness. But again, most of this evidence is circumstantial and sometimes contradicted by other research.

While the link between birth control use and the brain is worth studying further, it’s also not something to panic about just yet, according to Herrera.

“Women should not be too concerned about these associations, as there currently is not enough information to change hormonal contraceptive use based on this and similar studies,” she said. At the same time, anyone who feels they’re having too negative of an experience with their birth control for any reason should definitely talk with their doctor.

“There are so many different formulations of hormonal contraceptive on the market that with some thoughtful discussion with her physician she can likely find a new prescription that may come with fewer negative side effects,” Herrera said.