Oral contraceptives, also known as birth control pills, are used by more than 150 million women worldwide. About a third of teenagers in North America and Europe use them, making them the most prescribed drug for teenagers.
Oral contraceptives are known to have the power to alter a woman’s menstrual cycle. What is less well known is that they can also have an effect on the brain, particularly in areas important for emotion regulation.
As a PhD student and professor of psychology at UQAM, we were interested in the effect of oral contraceptives on brain regions involved in emotional processes. We published ours results in the scientific journal Frontiers in Endocrinology.
How does the pill work?
There are several methods of hormonal contraception, but the most common type in North America is the birth control pill, specifically, combined oral contraceptives (COCs). These consist of two artificial hormones that mimic one of the types of estrogen (generally ethinylestradiol) and progesterone.
Like the natural hormones, known as endogenous hormones, the artificial hormones contained in the pill, known as exogenous hormones, have an effect on the brain. They bind to receptors in different areas and signal the brain to reduce the production of endogenous sex hormones. It is this phenomenon that leads to the cessation of menstrual cycles, preventing ovulation.
In other words, when using COCs, users’ bodies and brains are not exposed to the fluctuations in sex hormones normally seen in naturally cycled women.
The effects of the pill on the brain: neuroscience to the rescue!
When they start taking COCs, teenage girls and women are told about their various side effects, mostly physical (nausea, headaches, weight changes, breast tenderness). However, the fact that sex hormones affect the brain, particularly in areas important for emotion regulation, is not generally discussed.
Studies have associated COC use with poorer ability to regulate emotions and one higher risk of psychopathology.
In addition, women are more likely to suffer than men anxiety and chronic stress disorders. Given the widespread use of COCs, it is important to better understand their effects on the anatomy of brain regions responsible for emotional regulation.
Therefore, we conducted a study to examine the effects of COCs on the anatomy of brain regions involved in emotional processes. We were interested in outcomes related to their current use, but also in the possibility of lasting effects, that is, whether COCs could affect brain anatomy even after women stopped taking them.
To do this, we recruited four profiles of healthy subjects: women currently using COCs, women who had used COCs in the past, women who had never used any method of hormonal contraception, and men.
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Using brain imaging, we found that only women currently using COCs had slightly thinner ventromedial prefrontal cortex than men. This part of the brain is known to be essential for regulating emotions such as fear. The scientific literature shows it the thicker this area is, the better the emotional regulation will be.
COCs could therefore alter emotional regulation in women. Although we have not directly tested the relationship between brain morphology and mental health, our group is currently investigating other aspects of the brain and mental health that will allow us to better understand our anatomical findings.
A dose-related effect, but this does not last
We tried to better understand what could explain the effect using COC in this brain region. We found that it was related to the dose of ethinylestradiol. In fact, among COC users, only those using a low dose of COC (10-25 micrograms) – not a higher dose (30-35 micrograms) – were associated with thinner ventromedial prefrontal cortex.
It may seem surprising that a lower dose was associated with a brain effect…
Since all COCs reduce endogenous sex hormone concentrations, we suggest that estrogen receptors in this brain region may not be sufficiently activated when low levels of endogenous estrogen are combined with low intake of exogenous estrogen (ethinyl estradiol).
Conversely, higher doses of ethinyl estradiol could help to achieve sufficient binding to estrogen receptors in the prefrontal cortex, simulating moderate to high activity similar to that of naturally menstruating women.
It is important to note that this lower gray matter thickness was specific to current COC use: women who had used COCs in the past did not show thinning compared to men. Therefore, our study supports the reversibility of the effect of COCs on brain anatomy, particularly ventromedial prefrontal cortex thickness.
In other words, COC use could affect brain anatomy, but in a reversible way.
And now?
Although our research is not directly clinically oriented, it helps advance understanding of the anatomic effects associated with COC use.
We are not asking women to stop using their COCs: adopting such a discourse would be both hasty and alarming.
It is also important to remember that the effects reported in our study appear to be reversible.
Our goal is to promote basic and clinical research, but also to increase scientific interest in women’s health, an area that is still understudied.
