Scientists warned about unexpected danger of contraceptives

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 discontinuing 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 consider the influence of sex hormones, particularly estradiol, which plays an important role in memory formation and fear suppression, as one possible risk factor. 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 team led by Lisa-Marie Davignon from the University of Quebec conducted a two-day experiment involving 147 healthy volunteers. The study included men, women with natural menstrual cycles, current users of oral contraceptives, and women who had stopped taking them more than a year ago.

Participants were trained to associate certain signals with a mild electric shock in one virtual context ("threat"), and then to extinguish this fear in another, safe context. The next day, researchers tested whether fear returned in the safe environment. The reaction was assessed by skin-galvanic response and functional MRI data.

The results showed that gender and natural estradiol levels did not affect fear in a safe context. However, women taking birth control pills showed significantly higher fear in a safe environment than those who had never used them. A similar effect was observed in former contraceptive users, indicating possible long-term changes in the fear regulation system.

Additional analysis revealed a dose-dependent effect: the greatest disturbances were observed in women taking medications with high doses of ethinylestradiol. No differences in response to real threats were found between groups - the changes exclusively concerned safe conditions.

MRI data showed that enhanced fear is associated with reduced activity in the hippocampus and ventromedial prefrontal cortex - brain regions responsible for context recognition and fear suppression. These areas are sensitive to estrogens, which is consistent with the experimental results.

In the future, scientists plan to study these effects in women with clinical anxiety and evaluate the role of other hormonal components of contraceptives.