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Does the pill change your brain?

If you've seen the headlines about brain-shrinking birth control pills, keep calm and read on.

A team of researchers at UCLA and Harvard published a study that has inspired creepy headlines like: “Are Birth Control Pills Shrinking Your Brain?” Um, no. And anyone who has actually read the study can tell you that.

What the research found

The study looked at 90 women—about half of them were taking the pill and half were not taking any type of hormonal contraception. The researchers took brain scans and did a bunch of fancy math. They found that:

  • Women not on hormonal birth control whose last period had started 2-6 days before showed some thicker regions of the brain. (BTW, “thicker” and “thinner” in this study were measured in tenths of millimeter, or about the width of a piece of paper.)

  • Just a few days later, from 18-24 days after the start of a period, these same regions of the brains of the women who weren’t on hormonal birth control were slightly thinner.

  • In women taking the pill, these same brain regions were slightly thinner, but there were differences between women taking active pills or sugar pills. For women taking sugar pills, some regions of their brain were as thick as women in days 18-24 without birth control.

In other words, it’s true that naturally occurring lady hormones affect women’s brains. Just like dude hormones affect men’s brains. That’s the one thing the science seems to agree on. It doesn’t agree on much else: of the three studies that have looked at possible associations between hormones, birth control, and the brain, no consistent patterns have been found.

What the research DIDN’T find

Here’s the final sentence of the report: “Whether [the observed change in brain thickness] is causally related to oral contraceptive use, and the functional significance of this cortical thinning, remain to be investigated.” In plain English: they don’t know what is causing these types of changes. And they don’t know—in fact, this study didn’t even try to investigate—what these types of changes mean for mood and other behavior.

The good news is you don’t have to trash your pill pack or switch methods. The not-so-good news is you wouldn’t know it from the way this study has been covered.

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