What’s your birth control doing to your brain?

Any woman starting on a birth control pill is warned about some of the physical and emotional effects of those additional hormones floating around in your bloodstream: weight gain. mood swings. acne. headaches. If you’ve followed along popular science reports, you may even have heard that being on the pill could change what kind of person you’re attracted to. Surprisingly, relatively little attention is paid to the fact that those effects result from hormones getting into your brain, insinuating themselves between your brain cells and changing the way they talk to each other. No one warns you that being on the pill might change the very structure of your brain….because researchers haven’t looked that closely to find out if it does.

Fortunately, the latest research is probably good news for women on birth control. Certain varieties of the pill do change the structure of some specific regions in your brain, but those changes might just be for the better, helping women recognize faces.

The original contraceptive informational insert. Photograph by US FDA; used under creative commons license.

The original contraceptive informational insert. Photograph by US FDA; used under creative commons license.

Two regions of the brain play a special role in recognizing faces. One is the fusiform gyrus, also called the “fusiform face area” because it seems to be central to our ability to recognize peoples’ faces; damage to this region of the brain can make it impossible or people to recognize faces (prosopagnosia or face blindness). The other is the nearby parahippocampal gyrus, also called the “parahippocampal place area”, which seems to be very important for our visual memories – for places, obviously, but also for famous faces. If the birth control pill does alter these regions, making them smaller or larger, it could also change how easily we can recognize a familiar face.

Now, studying the impacts of birth control pills is tricky because there are so many of them, and they can work in different ways. We often simplify the name to “the pill”, but there are dozens of brands that use different main chemicals. One major distinction is  based on how pills relate to the male sex hormone androgen. “Androgenic” pills (including chemical names Levonogestrel, Desogestrel, Norgestimate, and Gestoden), can mimic androgen and are more likely to have side effects of acne and hair growth, while “anti-androgenic” ones (including chemical names Drospirenone and Dienogest) do not. Because these categories have different impacts on androgen, they probably also have different impacts on the brain.

So, researchers compared women in their 20s to early 30s who were not taking birth control pills, who were taking androgenic pills, and women who were taking anti-androgenic pills. All of these women had their brains scanned with an MRI machine, to look for differences in gray matter (made up of the bodies of your brain cells, and the synapses they use to receive information). They also tried to memorize 30 faces, seen for only 3 seconds each.

Women who were taking the anti-androgenic birth control pills (which include brand names like Yasmin) had more gray matter in both the fusiform face area and the parahippocampal place area, and were better at recognizing faces than women who were taking the androgenic birth control or weren’t taking birth control at all. The improvements aren’t too dramatic – an increase from about 75% correct for women taking no birth control or the androgenic pills, to about 80% correct recognition for women taking the anti-androgenic formula – but they do suggest that the right birth control pill will grow the regions of your brain that help you recognize faces. And these advantages could keep building up; the longer women had been taking the pill, the more their gray matter in those regions had grown.

That’s the good news. There is also a hint of bad news, for women who (like me) take the androgenic version of birth control. Although their facial recognition abilities and the gray matter in their fusiform face areas and parahippocampal place areas was the same as women who weren’t taking birth control, they negative side effects of birth control may include changes in another region of the brain. These women had slightly less gray matter in areas of the frontal lobe, which is usually linked to important skills like working memory, planning, and emotion regulation. The researchers didn’t have the women do anything that would tell us if these differences in gray matter showed up in how women behaved, so it’s hard to say whether these changes were enough to

Of course, life in general leads to growth in some brain regions and shrinkage in others. My first thought was back to the question of pregnancy. I wonder what what hormonal soup the adult woman’s brain usually marinated in, centuries ago when birth control pills weren’t an option and women spent a large chunk of their adult lives pregnant or breastfeeding. Pregnancy changes the brain in many ways, including making mothers more sensitive to emotional facial expressions. Are anti-androgenic birth control pills mimicking the effects of pregnancy, trying to prepare brains to recognize new faces that might be encountered (or, to give the parahippocampal place area more to do, remember the spot where she left that bottle?) with some costs like “momnesia“.

Perhaps the most important reminder from this research is that we don’t know the full impact of long-term use of medications; most clinical research focuses on the impacts to our health, not to subtler questions about our personality and cognition. But then, we also don’t know what “normal” brains are supposed to be like, because we have changed our environment and our lifestyles so much from what they used to be. Personally, this evidence of subtle brain changes isn’t enough for me to drop my (androgenic) prescription, or hunt around for a new (anti-androgenic) brand. But I would like to see more awareness that every medicine we take might be sculpting our brains.

Pletzer, B., Kronbichler, M., & Kerschbaum, H. (2015). Differential effects of androgenic and anti-androgenic progestins on fusiform and frontal gray matter volume and face recognition performance. Brain Research, 1596, 108-115.


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