A new study out from the University of California, Irvine found that hormonal contraception influences how women remember emotionally provocative events, compared to women who aren't on birth control. Specifically, naturally cycling women may retain more details about an emotional event (i.e. the type of car involved in a fatal car accident, the accident setting, etc.), whereas women taking birth control pills may better recollect central information, or the "gist" of it.
This adds to the body of research findings of how hormonal birth control quietly tinkers with our cognitive functioning, stress and behavior. The study authors, for instance, mention recently established correlations between oral contraceptives and the brain's gray matter volume, improved verbal memory and a lowered stress response. On Stuff Mom Never Told You, we've also discussed how oral contraception in particular may lower women's libidos and affect short-term and long-term mating choices. The UC Irvine study authors didn't explicitly describe which types of hormonal birth control the women were taking, however.
These correlations are likely tied to sex hormones, since previous studies have highlighted gender differences in memory formation and recall. Men tend to rely on their right brain hemispheres remember the "gist" of events, and women fire up their left brains to recall more supporting details and nuances. Oral contraceptives prevent ovulation by suppressing natural levels of estrogen and progesterone, replacing it with synthetic estrogen and progestins. Therefore, the suppression of estrogen and progesterone in women taking hormonal birth control may explain why, in the UC Irvine study, they did a better job recounting a gist of an emotional event, as opposed to the details. This doesn't mean that either group had superior memory skills; their brains merely called up information differently.