Sex and stress hormones can affect our memory. A recently published study sheds some light on the memory altering effects of one of the most widely used hormone regulating drugs: the birth control pill.

Neurobiologists at UC Irvine, says that hormonal contraceptives like the pill have a strong and measurable influence on the way women remember emotionally charged events.

The experiment involved 72 women who were either naturally cycling or on the pill, and every woman in the study viewed a brief narrated story containing emotionally arousing elements and neutral elements.

The results? The emotionally arousing narative told the story of a woman and her son, involved in a car accident, where it gets hit and the boy is critically injured. The emotional neutral narrative on the other hand simply has the car hitting a curb.

Both stories were accompanied by 11 photographs depicting the woman, her son, and the accident (although the 11 photographs were the same across both stories.)

The experiment continued a week later and tested women who were administered a surprise free recall test and found that women who were on the pill experienced enhanced memory of the overall events of the story, compared to neutral story conditions.

On the other hand, naturally cycling women demonstrated what the researchers describe as "enhanced memory of story details" (that there had been a fire hydrant next to the crashed car, or that the hospital had been light brown in color, for example), but not of overall events.

"What's most exciting about this study is that it shows the use of hormonal contraception alters memory," said Shawn Nielsen, one of the researchers involved in the study. "There are only a handful of studies examining the cognitive effects of the pill, and more than 100 million women use it worldwide."

The researchers' findings are published in the latest issue of Neurobiology of Learning and Memory

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