As a scientist with two years after her PhD training complete, I’ve realized time and time again the importance of effective scientific communication. I find value in reviewing the work of fellow colleagues and presenting it to an audience who has yet to be introduced to new findings.

I’ve mentioned before in previous “science-based” posts on this blog that science shouldn’t be intimidating, but oftentimes it comes across that way because many scientists are used to speaking with their peers. After years and years of school, training, and specialized research, technical terms become a part of one’s everyday jargon in the scientific research field.

So when I see scientific communicators like Bill Bryson—or in this post’s case, Dr. Sarah McKay—publish works meant for a general audience, I’m enthusiastic about reading them from a critical scientist’s point of view, and featuring them on this blog to pique your interest.

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The reason McKay’s book, The Women’s Brain Book, came across my (virtual) desk was because a fellow woman in STEM, Dr. Anjali Kasunich, and I connected on Instagram to form a “nerdy science girls” book club of sorts, because of our shared passion for disseminating topics in science for the general public. Anjali and I both thought TWBB would be a fascinating read for our inaugural IG Live book club series since it was expected to contain a hefty collection of peer-reviewed studies, simmered down to simplicity, in relation to a woman’s hormonal health and her brain.

TWBB has a chronological order to its chapters, with the book spanning over how a woman’s brain is formed, conditioned, influenced, and changed throughout all of life’s stages. Major external factors like the environment in which we grow up in, and the social connections we make, have a crucial impact on our general brain health as well.

Depending on your level of interest in a specific life stage and how it affects the woman’s brain, it’s easy to jump from one section to the other in the book without feeling incredibly lost. I decided to read the book in the “traditional” way, and while my background as a scientist made me familiar with some of the studies and concepts Dr. McKay mentions throughout the book, I found at least four key takeaways from the book that I thought were worth mentioning:

1. We are to be female, unless SRY has its way

My sub-heading title is not to be taken literally, but it refers to some interesting observations…

In the very first chapter of TWBB, McKay addresses an important detail – female brain development technically doesn’t take place right at conception, and its progression is based on whether or not the Y chromosome is present. If we define (in this context) a biological female as having two X chromosomes, and a biological male as having one X and Y chromosome, we can then understand why the presence of these chromosomes is life-changing.

McKay notes that when XY embryos are 6-8 weeks old, a gene known as the “sex-determining region of the Y chromosome” (SRY) is turned on. SRY allows for the development of the testes, as well as turns on several more genes that guide in other “male-associated” biological processes. Without the Y chromosome however, SRY and it’s associated genes remain off, and we become female!

I would have thought that if SRY has such a powerful role in male development, a similar gene would have a role in females, but that is not the case. I also found it interesting that while the presence of androgens (the family of male hormones that includes testosterone) turns on genes that involve the development of male organs and physical characteristics, the female hormone estrogen doesn’t have such a role in “feminization”. In fact, ovaries develop in the absence of testosterone.

We are conditioned to think that if A=Male, then B=Female, but perhaps we should think of it more like 0+A=Male and 0=Female. Nature prefers us to be female unless otherwise noted 😜.

2. Nature and nurture are equally important in brain development

Growing up in California, I remember seeing ads on TV—and later billboards, buses, and the metro when I moved to Los Angeles for grad school—for the First 5 California campaign, which emphasizes the importance of the first five years in a child’s life in regards to cognitive, physical, and emotional development.

In TWBB, McKay provides examples for which natural disasters could impact this development. One such example was an event that took place in Montreal in the late 90s. An ice storm left the city without power for 45 days, and researchers took it upon themselves to monitor women who were pregnant at that time to see how the development of their children was affected for years to come.

Understandably, the “Project Ice Storm” babies were born prematurely, and this also correlated to timing of a woman’s pregnancy (very early and very late stage pregnant women tended to have premature births). When the babies became toddlers, they not only had cognitive and language developmental delays, but attention deficits and behavioral problems as well. “Ice Storm Girls” had increased risk of puberty, obesity, and asthma, but interestingly, “Ice Storm Boys” tended to have more serious problems compared to the girls, and researchers hypothesize that this may be due to the fact that the female placenta is a more protective barrier against maternal stress hormones. While we can’t control the presence and timing of natural disasters, this study seems to demonstrate that external factors that impact a pregnant woman’s well-being can lead to striking outcomes in the development of her unborn children…

3. Hormone sensitivity and depression

I have struggled with depression as early as 18, but over the years, I have noticed that while it may be underlyingly chronic, there are certain periods in my life when the condition feels “stronger” than others. If I am to line up all the variables that could be involved, I automatically consider external factors contributing to stress, hormone fluctuations, and diet (quality and quantity of food, in addition to vitamin supplementation).

So I was certainly interested to see what sources McKay collected in regards to premenstural syndrome/ premenstrual dysphoric disorder, or PMS/PMDD. I am highly convinced that during a very stressful period of my life in late 2018 (the fourth year of my PhD, prior to the publication of my first paper…you can imagine), I was suffering from all symptoms associated with PMDD.

Some researchers have suggested that PMS is something that has developed out of social context, meant to “put down the woman” as a reason for her “inability” to perform activities. At first, I wasn’t sure how I felt about this because the way I see it, it is good to have a medical reason to explain why you feel certain symptoms at certain times of the month. Of course, each woman has a unique experience—unique symptoms, unique timings, you name it. I often found that in my situation, I had non-stop irritability, mood swings, intense bouts of crying, and physical issues like fatigue, sleepiness, and bloating that went on for half the month, only to quiet down around my period, but rise back up again within a few days after my period ended.

So, I did have these crazy symptoms, but sometimes it felt like I was under nature’s wrath for almost the entire month, or sometimes only in the two weeks before and after my period. Confusing in an understatement 🤷🏽‍♀️.

McKay’s note about a 2013 Canadian study titled “Mood in Daily Life (MiDL)” was able to find that in a cohort of women who were asked about their PMS-associated symptoms—without knowing they were being asked about PMS—there was no significant correlation that PMS phase influenced mood. The researchers suggested that the symptoms were more influenced by factors in a woman’s life that were external, like lack of social support, environmental stress, or poor health.

While this could be, I was relieved to see McKay included a note by Jayashri Kulkarni, a researcher who supports the study of endocrinology to understand what causes PMS. And when she said that “women may differ in their sensitivity to hormones, perhaps via genetic variations in receptor structure or number”, I wanted to stand up and scream RIGHT???? THANK YOU 😂! I’m sure some kind of specialized hormone profiling for women at different phases of their menstural cycle could bring SO much more insight into caring for unique sets of symptoms. And given that my family does have a (maternal) history of mental illness, I can’t help but hypothesize that my genetic make-up influences how reactive I am to the hormones in my body, and how that in turn can influence how I feel.

4. Estrogen’s importance in late life

Even though estrogen doesn’t seem to be “so important” in utero, we can see it has tremendous effects on our well-being as we get older. McKay noted several points about estrogen throughout the book, including the point that high levels of the hormone in young, fertile women are thought to lower schizophrenia risk (although, context is needed to clarify what is considered “high”), and that low levels of estrogen could exacerbate PMDD.

In the latter half of the book, McKay touches upon menopause, and how estrogen and glucose are essential players in menopausal outcomes. The brain’s main fuel source is glucose, and it is a greedy little organ consuming 20% of our resting metabolic rate (RMR). McKay mentions an interesting observation that women who’ve had their ovaries removed before menopause experience a critical drop in estrogen, and that this drop is associated with increased type 2 diabetes risk. This risk is similar in women after they experience menopause naturally, suggesting that estrogen may have an essential role in regulating glucose metabolism and lowering diabetes risk.

While we can’t fight nature on certain processes like menopause (although solutions like hormone replacement therapy are available, with McKay going into detail on that in the book as well), it’s eye-opening to see how such tiny molecules have an incredible impact on our metabolic processes and in turn, our physical outcomes and well-being. All the more reason to take care of ourselves as much as possible!

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McKay has done an incredible job compiling what is known about the field in regards to women’s health and the brain, but as she points out time and time again, there is still so much more that can be done to understand a woman’s biology and its impacts on her brain health.

Recently, the NIH and other research funding bodies have stressed the importance of including male and female subjects in future research projects—especially if you have any hope of wanting to have your research funded in the future. This is a great step in the right direction, but there is no doubt we have a lot of catching up to do, as well as needing to put in energy to shift the current social construct of how women’s health is perceived.

If you’ve ever been curious about what we know so far about women’s health and the brain, TWBB is certainly a resource for anyone in this regard, whether you have an extensive science background or not!