December 11, 2023

The contraceptive pill may impair the fear-regulating regions of a woman’s brain, new research has revealed.

Combined oral contraceptive (COC) pills prevent pregnancy, mainly by stopping ovulation from occurring. Around 150 million women use the birth control method across the world. However the pills—which are made up of synthetic hormones— can cause a variety of negative, mental side effects that are rarely addressed.

New research by scientists at the University of Quebec in Montreal, published in the journal Frontiers in Endocrinology, has found that these hormones may impact how fear is processed in the brain.

Although scientists already knew that various sex hormones affect fear processes in the brain, this research found that women taking the combined pill had a thinner ventromedial prefrontal cortex than men. This region of the brain is associated with emotional responses, as well as decision making and self control.

Contraceptive pill
A stock photo shows a woman reading a leaflet included with contraceptive pills. The pill may impair the fear-regulating regions of a woman’s brain, new research has revealed.

“This part of the prefrontal cortex is thought to sustain emotion regulation, such as decreasing fear signals in the context of a safe situation. Our result may represent a mechanism by which COCs could impair emotion regulation in women,” Alexandra Brouillard, a researcher at Université du Québec à Montréal and first author of the study said in a release detailing the findings.

These findings back up other previous studies on the effects of the pill. A 2022 study published in Frontiers in Behavioural Neuroscience, found that out of 72 people, those who used oral contraceptives felt more fear, anger and disgust, than those who did not. Another study published in 2016 in JAMA Psychiatry found that hormonal birth control was linked with higher antidepressant use and depression as a whole.

The Canadian researchers studied a group of women who were either using combined contraceptives, used to take them but not anymore or had never used them. They also studied men.

Multiple side effects are associated with taking the contraceptive pill. Women are usually informed of some physical side effects by their doctor, before starting to take the pill. However mental side effects, and changes in brain development, are “rarely addressed,” according to Brouillard.

“Considering how widespread COC use is, it is important to better understand its current and long-term effects on brain anatomy and emotional regulation,” she said. “As we report reduced cortical thickness of the ventromedial prefrontal cortex in COC users compared to men, our result suggests that COCs may confer a risk factor for emotion regulation deficits during their current use.”

Scientists have already found that women experience anxiety and stress more frequently than men. And hormone fluctuations, which are altered by taking the pill, could be a reason why.

Scientists found this effect in women who currently took the pill, but not women who had once taken it, but had stopped. This suggests that the effect of the pill on the cortex may be reversible. However, more research will be needed to test this theory.

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