What does birth control do to women’s ability to process fear?

Is birth control hurting women’s ability to let go of fear?
Medically reviewed by William Williams, MD

A few months ago, I was driving to an engaged couples conference to speak on fertility awareness methods as an alternative to hormonal birth control. Less than five minutes from the site of the conference, I heard a commercial about birth control come on the radio. The ad implied that women’s access to birth control was about to be drastically limited, with dire consequences. With new research out the University of Quebec suggesting that hormonal birth control (HBC) may interfere with women’s ability to process fear in a healthy way, I have to wonder if fear-mongering ads about the loss of birth control access are a targeted marketing strategy.

How does HBC hurt mental health?

10 years ago, voices in the fertility awareness and natural family planning (NFP) space who dared discuss birth control’s disastrous mental health effects–from anxiety and depression to other emotional disturbances and suicidality–were dismissed and outright ridiculed as paranoid zealots. Fast forward to 2024, and mainstream sources increasingly acknowledge HBC’s mental and emotional health impacts, albeit with caveats and insistence that the benefits probably still outweigh the risks. But exactly how might HBC hurt mental health? 

We know that fluctuating levels of estrogen and progesterone in a natural menstrual cycle help women maintain healthy emotional regulation [1]. Since HBC flatlines women’s hormones, or, more accurately, stimulates tiny hormonal spikes each day, it could be that the lack of normal hormonal fluctuation explains the negative mental and emotional health effects many women experience on HBC. 

A recent study done by researchers at the University of Quebec in Montreal and published in Frontiers in Endocrinology provides further evidence of HBC’s negative effects on users’ emotional regulation. The Quebec researchers sought to understand whether and to what extent HBC plays a role in users’ ability to healthily process fear, which is a key component of emotional regulation. Their findings suggest that hormonal birth control may actually alter the way users process fear [2].  

Who and what was researched?

The study observed healthy Canadian adults between the ages of 24-35. 139 women were separated into three groups: 62 current oral contraceptive (OC) users, 37 past users, and 40 women who had never used OCs. The study also included a control group of 41 men. Since women have historically been left out of neurological research, it was important for the researchers to compare men’s brains to women’s brains to recognize the base differences between the two sexes before making any conclusions.

Each participant provided a saliva sample for natural and synthetic hormone assessment and participated in an MRI scan that specifically focused on the fear-processing regions of the brain.

Hormonal birth control alters the thickness of a part of the brain that processes fear 

To understand how OCs affect the brain’s ability to process fear, we need to first understand a little about the ventromedial prefrontal cortex (vmPFC). The vmPFC is key for decision making, memory, emotional regulation, and more. Together, the amygdala, hippocampus, hypothalamus, anterior insular cortex, dorsal anterior cingulate cortex, rostral anterior cingulate cortex, and the vmPFC process fear. 

The amygdala, hippocampus, and vmPFC specifically are chock full of sex hormone receptors, and the researchers zeroed in on the vmPFC to see if birth control impacts fear processing. 

Thicker vmPFC tissue correlates with greater emotional resilience

VmPFC tissue thickness correlates with an ability to let go of fear and thus relax [3]. Thicker vmPFC translates to less generalized fear, greater mental and emotional resilience after trauma, and increased ability to let go of fear. Notably, feeling more or less fearful all the time, even about little things, is the predominant feature of generalized anxiety disorder. Thinner vmPFC generally translates to decreased tolerance of healthy kinds of fear, and greater fearfulness overall. 

In the study, only the women who were currently using hormonal birth control had thinner vmPFCs than the men. Since the vmPFC helps to regulate and inhibit our response to emotions, a change in its thickness could play a role in how women who are taking hormonal birth control can regulate fear. Lead researcher Alexandra Brouillard commented, “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 [OCs] could impair emotion regulation in women.”

The women on hormonal birth control, who had significantly thinner vmPFCs, would be expected to have a harder time calming down and “extinguishing” their fear. They would logically be more vulnerable to chronic anxiety than their non-user counterparts. This suggests not only that our hormones play a serious role in our brain structure, but also that altering those hormones may unnaturally affect brain tissue and functioning. 

Are women more predisposed to fear than men? 

The researchers also looked at the dorsal anterior cingulate cortex (dACC) of the participants’ brains, the part of the brain that promotes fear [2]. Like the vmPFC, the structure of the dACC was different between men and women. Compared to all three groups of women, the men’s dACCs were consistently smaller in volume than their female counterparts. Since larger dACCs correlate with higher levels of fear, this finding could explain why women, in general, tend to be more fearful than men. It also reinforced the understanding that our hormone fluctuations affect how the brain develops, as the process of hormonal fluctuation in men and women varies significantly. 

Are HBC’s effects on fear processing reversible?

Similar to non-users and the men, the women who had used OCs in the past did show thicker vmPFCs than the women still on it. This led the researchers to conclude that decreased fear tolerance due to OCs is likely a reversible problem. Since only the current OC users (but not past OC users) had a thinner vmPFC, the neurological effects of hormonal birth control may be reversible. 

What else should future HBC research clarify? 

Future psychological and psychiatric research needs to study women, and lots of them. The Montreal researchers explained that even though women suffer anxiety far more than men, “As of 2012, less than 2% of fear-related [research studies] were conducted on female brains” [2]. Concerningly, “male-only manuscripts are 9 times more common than female-only papers in neuroscience and psychiatry journals” [2]. Most troublingly, “Female underrepresentation is mainly driven by the assumption that sex hormone fluctuations would lead to increased variability in results, albeit this argument has not been empirically supported” [2]. Women who are naturally cycling should not be penalized for their biology. And women who are on HBC deserve to know how it might affect their fear processing in addition to other aspects of mental and emotional health. 

Future research also needs to take adolescent birth control use into account. We know adolescence is a particularly delicate period for brain development, so women who started using hormonal contraceptives during that time could theoretically have more severe brain alterations than those who only used them in adulthood. 

How does this impact what we already know?

A Newsweek analysis of the Montreal study noted that birth control’s impact on emotional regulation isn’t exactly news, since “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.”

What does this mean for the 150 million women who use HBC across the globe? Although the amount of research on its effects is increasing, there are still many unknowns regarding HBC’s long-term or permanent impacts on women’s health, especially in women who’ve used it for decades, and those who started using it in adolescence. 

Women are sometimes warned about some of the physical symptoms they may experience while on HBC, but there’s often less education about the neurological and/or emotional side effects, especially whether or not they may be reversible. This study’s findings that HBC may decrease women’s ability to healthily process fear represent the preliminary phase of extensive research that needs to be conducted to understand just how, how much, and how long HBC impacts brain health and emotional regulation. 70 years since the Pill’s introduction, this research is long overdue.  


[1] Casto KV, Jordan T, Petersen N. Hormone-based models for comparing menstrual cycle and hormonal contraceptive effects on human resting-state functional connectivity. Front Neuroendocrinol. 2022 Oct;67:101036. doi: 10.1016/j.yfrne.2022.101036. Epub 2022 Sep 17. PMID: 36126748; PMCID: PMC9649880.

[2] Brouillard A, Davignon LM, Turcotte AM, Marin MF. Morphologic alterations of the fear circuitry: the role of sex hormones and oral contraceptives. Front Endocrinol (Lausanne). 2023 Nov 7;14:1228504. doi: 10.3389/fendo.2023.1228504. PMID: 38027091; PMCID: PMC10661904.

[3] Milad, Mohammed R et al. “Thickness of ventromedial prefrontal cortex in humans is correlated with extinction memory.” Proceedings of the National Academy of Sciences of the United States of America vol. 102,30 (2005): 10706-11. doi:10.1073/pnas.0502441102

Additional Reading:

Estrogen is a key driver of the menstrual cycle. But it impacts your brain health, too

FAM Basics: Your hormones during a natural cycle vs. your hormones on the Pill

Reasons Women Need Periods: The role of the menstrual cycle in brain health and development


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