Could Taking Birth Control Pills Make Women’s Memory More Like Men’s?

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A new study shows that taking birth control pills can affect women’s memory.

Shawn Nielsen, a graduate student in neurobiology and behavior at the University of California, Irvine, conducted a study with 66 female students, half of whom were taking oral contraception and half who were not.

The participants were given a unique memory test. Some women were randomly assigned to view an emotionally charged video about a young boy who was hit by a car while walking with his mother and then rushed to the hospital, where doctors reattach his severed feet. Other women watched a more neutral narrative in which the mother and son observe a minor accident and then go to the hospital to practice a disaster drill.

Nielsen, who is working toward her doctorate in the lab of Larry Cahill, a well-known hormone researcher, was interested in teasing apart how differences in estrogen and progesterone levels may affect memory. Previous research has hinted that estrogen may enhance verbal memory; in one study, for example, women taking oral contraception showed better recall of words on the active hormone days of their pill cycle than on days when they either weren’t supposed to take active pills or took non-hormonal substitutes.

In the current study, when women who viewed the emotional video were tested a week later about what they saw, those who were taking the pill were able to recall the general thread of the story better than its specific details. This is similar to how men remember emotional events, says Nielsen.

“If we reduce women’s sex hormone levels, the change in the type of information they recall is more like what a male participant might remember,” she says. The pill works by flattening out natural spikes in estrogen and progesterone — which is what triggers ovulation — and signals the body not to make additional hormones, keeping levels low throughout the cycle.

The results were the exact opposite for the women who weren’t on the pill: they were better at remembering details, such as what color shirt the boy had on, whether the mother wore glasses, or whether there was a fire hydrant at the intersection. The naturally cycling women couldn’t recall the general narrative of the story as well as they could these details.

This doesn’t mean that the pill squelches memory or that it robs women of their ability to recall salient things. It’s just a matter of what type of information they remember. Since the pill keeps hormone levels steady throughout the cycle, women who take it tend to react differently to emotionally charged experiences, compared with women undergoing the natural monthly ebb and flow of hormones. And that’s important since many of the mental illnesses that affect women — such as depression, anxiety and post-traumatic stress disorder — are extremely emotional in nature.

“What is important about these findings is that sex hormones affect the type of information recalled from an emotional event,” says Nielsen. “What that says to us is that these changes are a powerful tool for future studies investigating the underlying neurobiology of these disorders.

“Simply taking the pill and suppressing natural sex hormone levels can affect what type of information you remember from an emotional event. That speaks to the role that estrogen and progesterone play in memory — they affect how a woman remembers an emotional event in her life,” says Nielsen.

A better understanding of this connection could lead to more effective therapies that may target such hormonal drivers. Nielsen is already trying to figure out exactly what levels of hormones are associated with changes in recall. She is about to launch additional studies to correlate fluctuating levels of estrogen and progesterone in naturally cycling women with changes in the type of information they recall from emotional events.

The current study was published in the journal Neurobiology of Learning and Memory.

Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME‘s Facebook page and on Twitter at @TIME.

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