Birth control pills quite literally changed the course of history, giving women unprecedented control of their fertility and thus more freedom of choice in education, work, and family matters. But the most used form of hormonal contraception was developed before scientists understood the myriad functions hormones play in the body and brain—and some recent findings are highlighting how much is not yet known.
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Moving beyond the mean
Brain scanning research further supports the idea that hormone-driven biological changes could underlie the psychological side effects of birth control. Taylor, her supervisor Emily Jacobs, PhD, an associate professor of psychological and brain sciences at UCSB, and their colleagues have shown that hormones are even linked to daily changes in the structure of a woman’s brain.
The group collected brain scans from a woman for 30 consecutive days during a natural menstrual cycle, finding fluctuations in the volume of her hippocampus that correlated with changes in progesterone (NeuroImage, Vol. 220, 2020).
“We then collected scans while she was on the birth control pill and saw no volume differences across the 30 days we scanned her. That suggests that the pill’s control of her hormone levels was quashing the natural fluctuations of the brain,” said Taylor, who is now conducting a similar analysis of the whole brain.
It is no surprise, then, that researchers have documented a broad range of psychological changes linked to birth control use. In addition to changes in stress response and depression risk, hormonal contraceptives can lower libido and impact sexual attraction.
Pill use may also alter spatial reasoning, according to research by Adriene Beltz, PhD, an associate professor of psychology at the University of Michigan who studies gendered cognition. In a study that compared men, naturally cycling women, and users of two types of birth control pills, one group of pill users performed slightly better on a 3D mental rotation task than naturally cycling women (Hormones and Behavior, Vol. 74, 2015).
“The effects were present but small. We expect to see small effects because we’re studying highly complex behaviors that vary among people for so many different reasons,” Beltz said.
Read the full article on the American Psychological Association.
