In recent research, scientists have discovered a potential connection between the use of oral contraceptives and changes in specific parts of the brain responsible for processing fear. These findings may shed light on the gender disparities in fear-related mechanisms. It is well-established that hormonal fluctuations during the menstrual cycle can impact the brain’s circuitry related to fear. To gain further insight into the relationship between naturally produced sex hormones and their synthetic counterparts, Canadian researchers investigated the effects of combined oral contraceptive (COC) use. With over 150 million people utilizing oral contraceptives worldwide, this study could provide crucial insights into the consequences of prescribing COCs that contain synthetic versions of estrogens and progestogens.
The study focused on the ventromedial prefrontal cortex (vmPFC), a region of the brain that was found to be thinner in women currently using COCs compared to men. However, this effect appeared to be reversible, as it did not persist in women who had stopped contraceptive use or those who had never used oral contraceptives. It is important to note that these findings only suggest associations and do not demonstrate any known negative effects resulting from changes in the size of specific brain regions. Nevertheless, the researchers believe that further exploration of this topic could be beneficial. Alexandra Brouillard, a physiologist at the University of Quebec in Montreal, explains that this part of the prefrontal cortex is believed to be responsible for emotion regulation, such as reducing fear signals in safe situations. The thinning of the vmPFC observed in women using COCs may potentially impair emotion regulation in this population.
To gather data, Brouillard and her colleagues examined a group of healthy adults aged 23 to 35, including 139 women. Out of these women, 62 were currently using COCs, 37 had previously used them, and 40 had never used any hormonal contraceptives. The study also included 41 men for comparison purposes, as women are more prone to anxiety and stress disorders. The researchers measured levels of both natural and synthetic sex hormones in participants’ saliva and utilized magnetic resonance imaging (MRI) to scan their brains, specifically focusing on fear-processing regions. The study found that changes in the size and thickness of the vmPFC were associated with both natural and synthetic sex hormones, with women currently using oral contraceptives exhibiting a thinner vmPFC compared to men. Additionally, the study revealed variations in the structure of the dorsal anterior cingulate cortex (dACC), a region associated with fear promotion, between men and women. This suggests that naturally-produced sex hormones can influence brain structure.
The findings regarding brain structure indicate that men typically have smaller dACC volumes compared to women, along with thicker vmPFC volumes in comparison to COC users. This contrast may represent structural vulnerabilities to psychopathologies that predominantly affect women. A larger dACC in women could signify a predisposition to fear promotion, while COC use might exacerbate this vulnerability by potentially thinning fear-inhibiting regions such as the vmPFC. However, the study also found that the effects seemed to dissipate after discontinuing COC use, highlighting the need for further research to fully understand the impacts. It is crucial to remember that changes in brain region size do not necessarily equate to negative effects on an individual’s emotions or behavior.
The underrepresentation of women in both animal and human research is a significant obstacle in comprehending why women are more susceptible than men to anxiety and stress-related disorders. The exclusion of women from these studies is often due to the perception that hormonal fluctuations would introduce greater variability in the results. Unfortunately, this bias towards studying men has resulted in serious consequences. Alexandra Brouillard explains that when prescribing COCs, girls and women are informed about the physical side effects of the hormonal changes, such as the abolition of the menstrual cycle and suppression of ovulation.
The study linking oral contraceptives and changes in brain regions associated with fear demonstrates the complex relationship between sex hormones and brain structure. While further investigation is necessary, these findings provide valuable insights into the potential impacts of using COCs containing synthetic hormones. Understanding the mechanisms behind the differences in anxiety and stress-related disorders between men and women is essential for developing targeted treatments that address these disparities. By addressing the gender bias in research, we can strive for a more comprehensive understanding of the effects of hormonal contraceptives on the brain and overall health of women.