Birth Control Pills Alter Memory

Fran Lowry

September 26, 2011

September 26, 2011 — The use of oral contraceptives can alter the way a woman remembers emotional events, according to new research published in the September issue of Neurobiology of Learning and Memory.

After viewing an emotionally arousing story, women receiving hormonal contraceptives demonstrated enhanced memory of the central information about the story, or its gist, whereas women who were not receiving hormonal contraceptives showed an enhanced memory of the story details, but not the gist.

"There have been only a handful of studies that have looked at the effects of birth control on memory. This is the first to study emotional memory," lead author Shawn E. Nielsen, PhD, from the University of California, Irvine, told Medscape Medical News.

Dr. Shawn E. Nielsen

"What is most exciting about this study is that it is showing that the use of hormonal contraception alters memory. There are a number of disorders of emotional memory that disproportionately affect women, such as posttraumatic stress disorder, anxiety, and depression.

"If this is in any way connected to how women remember an emotional event in their lives, it may provide insight into the underlying neurobiology. Are sex hormones involved? How do they interact with stress hormones? This is a good starting point from which to begin that research," Dr. Nielsen said.

Headed by neurobiologist Larry Cahill, PhD, the investigators randomly assigned women who were receiving oral contraceptives and those who were not to view an emotional story or an emotionally neutral story presented as slide shows.

Both had 11 slides and showed the same images, but the narrative associated with each image was different.

"In the emotional version, a mother and son are walking along, the child gets hit by a car, they rush into the hospital, and they try to reattach his severed feet, so it's pretty emotionally arousing," Dr. Nielsen explained.

"In the neutral version, the mother and son are walking along, they pass the scene of a minor accident, they go to the hospital to practice a disaster drill, so it's a lot less arousing than the emotional version," she added.

Each participant's eye movements and pupil dilation changes were recorded as they viewed the story, and saliva samples were taken throughout the sessions to examine salivary alpha-amylase, a biomarker for norepinephrine.

A week later, the women were called in for a surprise memory test.

The researchers found that the women who were not taking oral contraceptives showed enhanced memory of story details, but not of central information, or gist, in the emotional compared with the neutral story conditions.

In contrast, the women using hormonal contraceptives showed enhanced memory of gist, but not story details, in the emotional compared with the neutral story conditions.

The researchers also found that eye movements while watching the stories showed that these differences in memory were not a result of differences in attention or the degree of arousal induced by the stories.

Commenting on the findings, Pauline Maki, PhD, professor of psychiatry and psychology at the University of Illinois at Chicago, who specializes in memory and brain function, said Dr. Cahill "is already well known for his phenomenal research linking sex to memory. The fact that women on oral contraceptives remembered different elements of a story tells us that estrogen has an influence on how women remember emotional events."

Dr. Nielsen and Dr. Maki have disclosed no relevant financial relationships.

Neurobiol Learn Memory. 2011;96:378-384. Abstract

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