The Period Brain: The New Science of Why We PMS and How to Fix It—A Manifesto for Women

by Sarah E. Hill

Do you feel like you’re riding a premenstrual roller coaster every month that leaves you feeling hungry, tired, angry, sad, and unsexy?

Leading researcher and women’s hormone expert Dr. Sarah E. Hill explains why we feel so universally icky before our periods— and what to do about it. The problem isn’t that women are hormonal; the problem is that the second half of the menstrual cycle—the luteal phase, when the hormone progesterone rises and estrogen decreases—has been systematically ignored by science and medicine.

Progesterone is at the heart of every feeling we associate with PMS: it affects our daily sleep and calorie needs (hello, cravings!); whom we’re attracted to; our sex drive; and—as every woman can attest—our mood. Because the luteal phase is understudied, every bit of health, diet, and relationship advice you’ve followed is based on that first, estrogen-glow half of the month or, worse, was designed for men.

The rules that work for us in the first two weeks of the cycle don’t always fit in the second, causing most of us to spend half the month following advice that is completely at odds with the way our bodies work at this time. It’s no wonder we feel awful! Dr. Hill demystifies how our bodies work, so you can work with your hormones to:

· Sidestep PMS “cravings” by eating more –you burn up to 11% extra calories in the luteal phase!

· Exercise in a way that’s invigorating instead of draining.

· Understand your sex drive, and why sex has different meaning across the month.

· Quit bad habits more easily thanks to progesterone’s addiction-busting properties.

· Navigate motivational and energy dips without added stress.

· Incorporate anti-inflammatory foods and habits to naturally ease PMS.

The Period Brain is a science-tested roadmap to understanding PMS and PMDD. It’s time we demand a better month, every month – and usher in a new era in women’s health. Period.

Genres: Nonfiction, Science, Health, Self Help, Feminism, Psychology, Medicine

304 pages, Hardcover

Published September 30, 2025

About the author

Sarah E. Hill, PhD, is an associate professor of psychology and a leading researcher in the dynamic and rapidly expanding field of evolutionary psychology.

Reviews

[Kelli]

Thanks to NetGalley and the publisher for an advanced copy in exchange for an honest review.

Hmm I feel very similarly about this book as I do about Come as You Are: The Surprising New Science that Will Transform Your Sex Life- love the message, learned a lot, but I just really don't like the writing style.

This is a short little book that explains female sex hormones (estrogen and progesterone), how they cycle each month, and the effects they have on your body and mind (aka PMS), in addition to tips on mitigating these effects. Her goal as a hormone researcher is to educate people with these hormones (she is careful to point out in the beginning that all bodies are not the same, and this does not apply in a strict gender binary at all) on how their body functions, because as she rightfully points out, most of us are never taught any of this stuff.

It was super interesting to learn about how my hormones work, testosterone included, and I really liked her perspective on PMS- that it only feels so bad because we do not understand what is going on and try to live our life as if we don't have hormonal cycles and feel crazy, rather than working with our bodies and adjusting our diets, exercise routines, and sleep to fit the needs of where we are in these cycles each month (of course, with the exception of some who have things like PCOS or PMDD requiring further care).

I am curious to try out some of her tips (you DO need more calories and sleep in the luteal phase!) and start to track my cycle a bit more going forward.

My only quip was that the writing style is not my favorite, as it comes across like a teenager trying to explain something (lots of cursing, pop culture references, simple phrasing, etc.) which is just not my preference when reading a book about science, though it might appeal to you! I also thought all the content of this book could be written in like a single long note, because there was a lot of repetition and too much " and that's what you'll find out soon" sort of thing, rather than just getting to the point.

[Carolyn]

I thought the science of hormones and their function in the body was beautifully explained. This topic was new to me and it was a nice introduction to understanding my cycle, the importance of listening to my body, and sexism in science and society at large. However, the book felt extremely repetitive at times, and sometimes the author would insert her own opinions in a way that felt too anecdotal for a science book. I would recommend that everyone learn about the female hormonal cycle, though!

[Abigail Franklin]

The science was interested and the practical advice was just “eat plants and move your body”

[Shelby]

The Period Brain was a super helpful, easy to understand approach to understanding the key differences between the follicular and luteal phases. I loved the guidance I gained, as I have read similar books, and learned new information of those differences. I wish there was a non-woman-only language used throughout for our fellow bleeders, but overall Hill did a wonderful job explaining.

*In addition, to the editor, the graphs needed some work for how the print came out.

[Kelsey Ebling]

Skimmed a lot, think I learned something? Basically, be in good health and your hormones will be fine. Maybe take some supplements.

[Elisabeth]

Who’d have thought biological sex was so important 🙃 Of course it is! Especially in the field of medical research.

This was so good. I enjoyed the way Dr. Hill wrote, and she had some amusing footnotes along the way, as well as plenty of great information. Most of the advice she gave wasn’t exactly news to me, but it did help to reinforce that I need to approach each part of my cycle differently.

[Aly Kim]

Even as an educated MD with interest and extra study in reproductive health I didn’t know the vast differences between the two phases of our menstrual cycle. Up to metabolism of medication. Very useful information with actionable steps and resources. Important work being done and I’m all for it.

[Emma]

Having a uterus is awesome

[Tatyana Läh]

Very informative and eye opening audio. Every woman should read

[Jade (beauty.andherbooks)]

I really enjoyed learning more of the science behind menstrual cycles and how it affects lots of our everyday lives. I wasn't a fan of Dr. Hill bringing evolution into the book, but that's personal preference.
My key takeaways were:
-Eat whole, unprocessed foods
-Minimize stress to support ovulation
-Melatonin production is lower in the luteal phase, so sleep disruptions are more common; limit caffeine intake

I definitely want to read Dr. Hill's "This is your brain on birth control book" as well!

[Emma N]

This is a great book! I enjoyed it and thought the statistics, experiments, and overall information shared was extremely helpful in understanding the menstrual cycle and women’s bodies better. The data makes so much sense and I took so many notes from this book because WOW every person needs to read this book

[Sarah Lawrence]

Super informative! Learned none of this in school lol. Feels pretty essential. Just unsure about the period tracking app that kept being recommended as it seems to be AI powered. Other than that good read!

[Bob Zhao]

the luteal phase do be wild.

[Kassondera]

Informative and easy to read, but a bit repetitive. I enjoy Sarah's writing style and voice, as it makes it easily digestible.

[Abby Nunns]

Such a great resource and made me not feel crazy!

[Dani Veuger]

*audiobook*

I found the biology parts of this very insightful and helpful. Although I always have skepticism, there are definitely good practices in here for any menstruating woman wanting to be healthy.

[Manda Ridds]

I don’t normally write reviews, but I felt the need to do so for this book. I’ll keep it short and sweet(ish).

I picked up this book to learn more about the science behind our menstrual cycles and some of the issues that typically plague us in the luteal phase. I have issues with PMS, so this book was of interest to me.

While I found some of the science helpful in this book, the book felt more like an overly opinionated ode to women that men are the bad guys and women are always left in the dust. I do agree that women need to be studied separately from men since we do have two different bodies, but I did not pick this book up to read about how men suck and women deserve more. It took away from the purpose of the book and had me frustrated every time I began a new chapter where I had to read more about how men have been studied more than women. I get it. The author is upset about the disparities between men and women. But why did she choose to insert her opinions about that in this book? I thought I was reading a book about science, not to be preached to about how women deserve more.

[Margaret Balwierz]

This book seems more like a conversation with a friend or a health influencer, rather than medical research. While Sarah E. Hill is a Evolutionary Psychologist, not a gynecologist or endocrinologist, she does seem to present the topic of menstrual health in a way that lay people can understand, especially since it not a widely discussed topic. I think this is a good book for a jumping off point to learn more about the menstrual cycle and how you need to adjust your life to work with your cycle, not against it. It brings up some worthwhile points of treating the whole body and system, rather than just the menstrual symptoms, BUT it is very generalized advice, and should definitely be talked about with your own health care providers. She seems to have a bias toward "natural" methods, which there is nothing wrong with, but again, should be talked about with a healthcare provider who knows your specific needs especially when introducing or coming off of any sort of supplements or medications.
I'm not a fan of her writing style, and while she tries to address medical misogyny and sexism, and the overall fear of topics relating to menstrual health, it comes across as more "boys suck" rather than a critique or a call to fix the broken system to provide better understanding and research support for these topics.
Thanks to NetGally and William Morrow for this ARC.

[Madison Geery]

Every woman should read this book. This book peeled back the curtains to share impactful our cycles were on every single aspect of our body (and how medications impact us differently at different points in our cycle)! I loved the recap sections at the end of each chapter with helpful guidelines of how to optimize your health in realistic ways. Thank you to netgalley and the publisher for an advanced copy of the review for my honest feedback!

[Jenna]

I recommend this book far more than I actually enjoyed it. Her tone was pretty annoying, the advocacy stuff didn't need to be mentioned every chapter, and there were some chapters that just weren't very interesting/useful to me (I already know how to eat well). BUT it has SO much good information that women need to know and I learned quite a bit.

[rhizo]

literally could not have told you anything about what progesterone does, how estrogen and progesterone cycle in a biologically female body or how progesterone affects immunology and efficacy of treatments. now i can! we call that a success story. review pending 😊

[Laianna]

Understanding your cycle in 2026 can sometimes feel like studying folklore. You understand that there must be scientific explanations for the myths and legends, but no one, not even your doctor, seems to know the full story.

This book can help.

In spite of the author’s chatty tone, which occasionally detracted from my reading experience (e.g., I know what “feels like shit” means, but when it comes to a medical condition, I’d prefer to know the actual symptoms), I learned so much.

Most women who track their cycles understand the basic pattern. Even if we don’t have the words for the four distinct phases (menstruation, follicular, ovulation, and luteal) we know that after our periods, we feel energized and confident, and before our periods we feel emotional and tired. Older women warn about “the curse,” tampon commercials joke about the “monthly gift,” and men leer about “that time of the month,” but the worst time for many of us is actually the luteal phase, right before our periods rather than during.

After reading this book, I finally understand why.

Women have two primary sex hormones, which play different roles. Estrogen, the most famous one, rises in the first two weeks of the cycle (menstruation, the follicular phase, and ovulation), giving us the energy and confidence to flirt, build strength, and have sex, and progesterone, the culprit behind the luteal phase, rises during the last two weeks of the cycle, preparing our bodies for pregnancy by weakening our immune systems and increasing our sensitivity to threats. It is not that our bodies simply turn on us during the progesterone-dominant luteal phase, but rather that we have different needs and desires which we never learned to address.

The author goes into detail explaining myriad flaws in medical research which have led us to ignore our bodies’ signals, but the gist is that most studies and health guidelines include men as the baseline, without taking into account the hormonal fluctuations that define us as women. If women are studied at all, it is usually during the 20% of their cycle when their hormones are at their lowest, aka when they most resemble men. The author advocates for a different approach in which women would be studied twice, once during the follicular phase and once during the luteal, to fully capture the impacts of estrogen and progesterone, and envisions a world in which sex hormones would be included as a variable in medical research by default. It was sobering to read about how one Alzheimer’s medication which had opposite results in men and women has been shelved altogether, despite being effective for 50% of the population.

Despite the frustrating state of modern medical research, it was a relief to finally understand that during the luteal phase, progesterone weakens the immune system as part of a standard process to allow foreign DNA (i.e., a fetus) to breach the normal barriers of the body. This is why women with medical conditions like asthma, lupus, or multiple sclerosis might experience extra flareups during this time. Since our bodies are literally more vulnerable, we are emotionally and physically sensitive to threats. What most of us take for irritability and paranoia during this phase is actually heightened threat sensitivity and risk awareness. Our routines might be structured around the idea of consistent daily needs, but when we’re progesterone-dominant, we also need 7-11% more calories, more rest, and different types of exercise (walking or gentle yoga rather than cardio or strength training) than when we’re estrogen-dominant.

The author also addresses changing desires throughout the cycle. In the first two weeks, we tend to be attracted to people with good genes. In the second two weeks, we tend to be attracted to people with good partner qualities. Since sex is the foundation for a lasting relationship (due to the hormones released during intimacy) we still desire sex regardless of our dominant hormone; however, our motivations for wanting it change from satisfying an urge (estrogen) to connecting with an individual (progesterone).

In addition to all of the aforementioned cycle info, there are also chapters on nutrition (limit processed food, which is anything containing sugar or flour, and eat whole foods whenever possible), exercise, and other conditions like PMDD or mood disorders. According to the author, modern women are undernourished, with too much inflammation, too much stress, and too little social support. If we accommodate our individual cycles, rather than falling prey to a “one-size-fits-all” approach to health and wellness, we will experience fewer negative symptoms from our routine hormonal shifts and understand ourselves and the other women in our lives much better.

[Meg Hennessey]

Atrocious science and atrocious writing. I only managed to read a few chapters and skim a few more, as the innumerable scientific errors and poor communication style were too much to bear.

For starters: multiple graphs and illustrations are comically childish. They lack correct labels on the axis, error bars, p-values or any indication if the results are statistically significant. I imagine this is because the author wants this book to have a more "approachable" style, but the title is called "the New Science of Why We PMS" and the author leans a great deal on her scientific credentials. So it is also quite disappointing when you see her repeatedly leap to conclusions that should instead be the basis for research. One example is at the start of Chapter 7 where she plainly states on one topic: "This [has] only been studied in heterosexual men, but I am guessing that lesbian women find their partners sexier at high fertility too." Guessing?!? That is precisely the kind of question that would make for an interesting hypothesis, but certainly any researcher worth their salt would not presume to know what the answer would be. There are many other examples like this throughout the book, too many to list here.

Similarly in Chapter 7 she cites a statistic that 50-70% of women do not consistently achieve orgasm through intercourse alone as evidence that, in her words, "not all women's bodies are equipped to [orgasm]." This is an appallingly shallow conclusion, in part because there is a considerable body of research on this topic that shows many different factors influence whether a women can orgasm and how frequently (such as partner type, sexual education, cultural upbringing, prior experience, the list goes on and on). I am baffled why the author would draw the conclusion that this statistic indicates women just aren't meant to orgasm or why she would not reference other research in this field.

Speaking of references, you'll note that there are essentially no references cited throughout the book, only a compendium of papers listed at the end. So if you'd like to find which paper some statistic comes from, you have to just do your best to suss out which citation is most likely. This isn't the gravest error, but certainly does not lend credibility to the author.

Overall, this book reads as the manuscript of a researcher who lets her per-conceived notions guide what conclusions she draws from data, rather than the other way around. It doesn't appear the book went through any significant fact checking or review (there are multiple grammatical errors that presumably an editor would've caught). It seems much more in the vein of the numerous pop-science articles that are churned out just for a publication to have some content to show, rather than substance or validity.

While her purported mission - to help women understand their bodies- is admirable, this kind of "science" writing only helps to murky the waters. I'm not sure how this author runs a research lab of their own.

[Morgan Fisher]

Sometime in 2019, Sarah Hill’s This Is Your Brain on Birth Control popped up on an audible new release newsletter. The title was catchy and I, a long time user of the pill, was intrigued. I listened to the audiobook and repeatedly rewinded to replay everything, needing to hear the words two or three times. I was astonished at the suggestions, and although they were only just correlations, it sent me down a path to actually learn my body, something that I, at the time a 27 year old woman, had never done on this level. This was a catalyst for me to deep dive into other books about the fertility, hormones and women’s health and so I was stoked to see The Period Brain and eager to dive in, knowing Hill's research as a part of my hormone appreciation origin story.

Did I learn anything new? Yes, and no. I gained a deeper understanding of the superficial facts I have known for the last five years since going down this hormone rabbit hole and becoming a user of the Fertility Awareness Method. But, do I read only to learn new ideas? No, I read to learn and there’s helpfulness in repetition. If you were to only read one book about hormones though, I wouldn’t start with this one: I’d go for one of first four I list below.

What I liked :
+ The Science! I loved understanding what progesterone truly does in the body AND the brain, and the biological reasons, in addition to the research behind the science and how we’ve gotten the information we have so far
+ Learning about other products and resources in the market to expand my knowledge. I am now going to dive into the impacts of glucose and understanding inflammation
+ Chapters 6-10! I would re-read these in a heartbeat

What I Didn’t Like :
— Censorship of curse words: write them fully or don’t curse at all; ‘sh*t’ and ‘f*ck’ feel like they cheapen the text
— More charts and infographics would have been immensely helpful

Similar Books I Recommend :
This is Your Brain on Birth Control (Sarah E Hill)
The Period Repair Manual (Lara Briden)
Taking Charge of Your Fertility (Toni Weschler)
The Fifth Vital Sign (Lisa Henrickson-Jack)
Eve (Cat Bohannon)
All In Her Head (Elizabeth Comen)

Thank you to NetGalley and William Morrow Books for the ARC and the opportunity to read and review this title.

[Sophie]

A Severely Compromised “Girlboss” Manifesto…

Sarah Hill opens The Period Brain with an aggressive premise, framing this brief book as “one part science, one part PMS help” and an exposé on how modern medicine has historically “mishandled” women. Honestly? "Mishandled" is an incredibly weak, sanitized choice of words for an author whose previous, groundbreaking work basically proved that women have been systematically gaslit by the medical establishment.

Hill argues this manifesto is a starting point for discovering “who we all become in the two weeks of the cycle that the world decided to ignore,” specifically tracking the interplay of estrogen and progesterone. But if you are expecting the absolute mammoth, high-IQ breakdown we got in How the Pill Changes Everything (which I reviewed a few years ago—check that out [here]), prepare to be profoundly disappointed. Instead of building on that legacy, this release feels vastly scaled down. This isn’t a worthy sequel; it’s a massive downgrade.

Cringe, Clichés, and Watered-Down Science
After the massive success of her debut, the absolute lack of depth in this bite-sized volume is a total slap in the face. In attempting to craft a "manifesto" for a wider audience, Hill has aggressively dumbed down the material. The narrative flow is entirely nonexistent; it is just a choppy, disorganized mess.

Worse yet, the text is packed to the brim with superfluous pop culture references, desperate shorthand lingo, and gratuitous cursing. It feels less like "authentic feminist rage" and more like a corporate executive trying to write a edgy Netflix teen drama. Frankly, it reads like it was written for an 11-year-old who just discovered the word patriarchy on Roblox—and even they would find it incredibly cringe and nowhere near informative enough.

The Verdict: Hill claims this is a revolutionary manifesto, but it reads like it was stripped of substance just to trend on TikTok.

As feminist readers, we are sick to death of being handed watered-down, "pop-science" crumbs and corporate "girlboss" shorthand. We were ready for rigorous, unapologetic science, but Hill completely failed the assignment by catering to the lowest common denominator. If you are craving real depth, skip this side-quest entirely; you won't find it here.

[⋆˚꩜｡⋆ Lisa - Can't talk, reading...]

The Period Brain blends popular science and the latest research with health and lifestyle advice in an interesting exploration of how the luteal phase works and why a better understanding of this phase of the menstrual cycle is important to naturally cycling women's overall health.

Sarah E. Hill is clearly passionate about women’s health and demonstrates how a system based on the male body as the default fails to account for the female body’s intricate dual hormonal system and cyclic nature (“bikini medicine”), which has led to the exclusion of women from the medical system and a great deal of ignorance, stigmatisation and medicalisation around our normal hormonal fluctuations.

The author argues that when we stop applying what works for the male body's testosterone-based ‘steady state’ to the female body, we can start feeling and functioning better throughout the month. She provides insight into the luteal phase and how we can sync diet and lifestyle around the effects of progesterone on the brain and entire body for a smoother transition from ovulation to menstruation. I couldn’t agree more that one-size-fits-all recommendations have been given to women for too long, meaning that we are so often working against our hormones instead of with them. This mismatch, argues Hill, is a contributing factor to PMS.

The book ends with a moving and convincing rallying cry for equality in research, medicine and pharmacology for a future where women are no longer seen as small men and where we reimagine our relationships with our bodies, focussing on wisdom, not pathology, so that we can celebrate our cycles as normal and wonderful.

[Reader]

I was so hopeful this book might contain new science and solutions for coping in the luteal phase, but it has nothing to offer, besides a ridiculous attempt at reframing the problem out of existence. I was hooked by the suggestion that “feeling awful half the time doesn’t make evolutionary sense”, but the author goes on to offer few solutions for feeling better besides the standard advice on sleep and diet.

The author’s groundbreaking new suggestion is that when we are struggling with PMS, we are simply failing to understand that the discomfort we are experiencing is a result of normal changes in the body.

I don’t know about anyone else, but I picked up this book searching for practical, applicable solutions to cycle discomfort because I do not wish to accept it as normal. Understanding that these symptoms (and yes, they are negative symptoms, as much as the author would like to deny that) arise from the body preparing for pregnancy does not do anything to mitigate their life-interrupting potential.

The writing is repetitive, tangential, and overly political. If you’ve read any other book about the female cycle before, it has nothing new to add.

[Abby]

A good deal of what you’ll find in the “hormone health” world is pure conjecture, leaving women to cobble together a trial-and-error and word-of-mouth approach to hormonal sanity. Sarah Hill does a wonderful job explaining why this is: studying women has historically been “too hard” for Big Science. The standard for including women in clinical studies is to ensure they are on days 3-7 of their cycles: a time when hormones are lowest (and they are most similar to men hormonally). This would be fine if variations in cycle phase didn’t matter much, clinically. But as Hill shows, 1) this is an assumption much scientific research makes without any evidence and 2) what evidence does exist suggests a significant difference.

The second half of the book looks at the limited research on ways to improve hormonal health and well-being, including Hill’s own studies. With a critical and reasonable eye, she demonstrates how the available science vindicates intuitive concepts like nutrition and exercise cycle syncing, while being honest about what practices have yet to be rigorously studied.

[Ula Tardigrade]

After centuries of neglect, the female body is finally becoming visible in Western science. There is an increasing amount of discussion about the differences between our bodies, as well as how research has traditionally focused on men. This has led to many misconceptions and blatant biases. This is most evident in the formerly taboo topic of menopause. Not only are there many new articles and books examining this phenomenon, but it has also become part of popular culture. Just look at TV shows, from Fleabag to the recently released Riot Girls.

It's about time we start talking about periods and PMS in a levelheaded manner, too. This is exactly what this book is about. Blending popular science and self-help genres, it provides all the facts, personal stories, and practical tips. It's certainly worth reading!

Thanks to the publisher, William Morrow / Harvestand, and NetGalley for an advanced copy of this book.

[Sophia H]

I’ve decided to give writing a book review a try, so here it goes. This book was 3 stars, averagely good as I feel i’ve walked away from reading this with more knowledge than I had prior to starting it. I’m not one to typically this genre of book: non fiction, self-help etc. but I was satisfied with what I learned from this as the information proved how little research is done on women’s health and wellness and how much more research and studies need to be done. A woman’s luteal phase and menstrual cycle in general is individualized and complex and we have to go digging for information on our own as there is no “one size fits all” method to deal with the hormones, moods and symptoms that occur within this phase. Even though at some parts the information felt redundant, it has made me intrigued to learn more as this affects a woman every month. Overall, this book provided a solid foundation to the complexities of the women’s luteal phase.