Contraceptive pills could change fear-promoting part of the brain: Quebec study

Study found that a brain region that decreases fear signals was thinner in women who currently use oral contraceptives

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Researchers in Quebec have uncovered a possible link between oral contraceptives and the regions of the brain that help us process and regulate fear.

For their paper “Morphologic alterations of the fear circuitry: the role of sex hormones and oral contraceptives,” researchers from the University of Montreal and the University of Quebec recruited 139 women and 41 men between the ages of 23 and 35.

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The women were identified as current users of oral contraceptives, previous users and those who had never used them. The researchers used magnetic resonance imaging (MRI) to measure volume and thickness for regions of the brain that influence fear processing.

Scientists already knew that sex hormones (both naturally produced and those found in contraceptives) can have an impact on brain morphology. It’s also understood that woman are more likely than men to have anxiety and stress disorders.

The researchers noted that a brain region known as the ventromedial prefrontal cortex was thinner in women who currently use oral contraceptives than in the men in the study. But they also noted that there was no difference in thickness for women who had previously or never taken the pill. This suggests that any physical change is temporary and reversible.

“This part of the prefrontal cortex is thought to sustain emotion regulation, such as decreasing fear signals in the context of a safe situation,” lead researcher Alexandra Brouillard told the web site sciencealert.com. “Our result may represent a mechanism by which [oral contraceptives] could impair emotion regulation in women.”

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The key word in that statement is “could.” The study did not look for any psychological changes among the participants, and the researchers were at pains to point out that changes in brain region size do not necessarily correlate to changes in behaviour.

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Even so, the study did suggest possible effects. The men showed a smaller volume of a fear-promoting region of the brain than the women, regardless of their contraceptive use.

This, the researchers wrote, “could represent a female predisposition to fear promotion, whereas [oral contraceptive] use could exacerbate this vulnerability by potentially inducing a thinning of a fear-inhibiting region.”

They added: “As tempting as it may be to settle on this conclusion, caution must be exercised when interpreting interrelations between brain morphology and behavioural or psychological data. Despite the high reliability of structural imaging, the validity of brain-behaviour associations has been criticized.”

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They also noted that more research should be done on younger women. “Given that adolescence is a sensitive period for brain development and that oral contraceptive use at this age has been linked to a higher vulnerability to depression, oral contraceptive parameters (e.g., duration of use and age of onset) may be other relevant and possibly more sensitive factors for studying durable effects,” they wrote.

“Of note, our team is currently investigating the effects of these parameters.”

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