17 Jan , 09:56
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Taking oral contraceptives may affect how women's brains regulate fear in non-threatening situations. This conclusion was reached by an international team of researchers. The authors proved that women taking birth control pills - especially those with higher doses of synthetic estrogen - express stronger fear in "safe" contexts than those who have never used hormonal contraception. Moreover, such changes may persist long after discontinuation of the medication. The work is published in the journal Neuropsychopharmacology (NPP).
Anxiety disorders and post-traumatic stress disorder occur in women almost twice as often as in men. Scientists suggest that one of the key risk factors may be the influence of sex hormones, particularly estradiol. This hormone plays a crucial role in memory formation and fear suppression mechanisms. For this system to function normally, the brain must clearly distinguish between dangerous and safe contexts - for example, a snake in the forest versus a snake in a terrarium.
A research group led by Lisa-Marie Davignon from the University of Quebec organized a large-scale two-day experiment involving 147 healthy volunteers. The study included several groups: men, women with natural menstrual cycles, current users of oral contraceptives, and women who stopped taking them more than a year ago.
Participants were offered a unique experiment: first, they were trained to associate certain signals with a mild electric shock in one virtual context (a "threat" situation), and then trained to extinguish this fear in another, safe context. The next day, scientists tested whether fear returned in the safe environment. Reactions were recorded using skin conductance response and functional MRI data.
The results were unexpected: participants' sex and natural estradiol levels did not affect the intensity of fear in a safe context. However, women taking birth control pills experienced significantly higher fear in the safe environment compared to those who had never used such medications. Notably, a similar effect was observed in former contraceptive users, suggesting possible long-term changes in the fear regulation system.
Further analysis revealed a clear dose-dependent effect: the most pronounced disturbances were observed in women taking preparations with high concentrations of ethinylestradiol. The researchers note an important nuance: no differences in response to actual threats were found between groups - the changes concerned exclusively safe conditions.
MRI data revealed the neurobiological mechanism of the effect: increased fear was associated with reduced activity in the hippocampus and ventromedial prefrontal cortex - brain regions responsible for context recognition and fear suppression. These areas are particularly sensitive to estrogen effects, which aligns well with the experimental results.
In the future, scientists plan to expand their research to include women with clinical anxiety, as well as to evaluate in detail the role of other hormonal components in modern contraceptives.
