Guest blog by Maria Theresa Sanchez


They say that men are from Mars and women are from Venus. While we certainly have more in common than species from separate planets, there are key biological differences between both sexes that impact our brain health in profound ways. One such difference is so central that it affects all six pillars of mental health as defined by the Cleveland Clinic: physical exercise, food and nutrition, medical health, sleep and relaxation, mental fitness, and social interactions. Care to guess what it is?


Yes, it’s all about the hormones

Hormones are essential in ensuring our bodies’ natural rhythms run smoothly. They are a key communication mechanism between different parts of the body, responding to changes in the environment and helping the body maintain homeostasis. Hormones regulate bodily functions, including development, growth, and metabolism, and impact systems such as reproduction, digestion, and brain health.

Hormones are a key difference between men and women, with variations in the types of hormones, their intensity, and their consistency. Hormones are both impacted by and have an impact on our body clocks, the biological rhythms that affect our daily lives. Both men and women have a circadian rhythm, responsible for regulating daily functions such as sleep, digestion, and the secretion of specific hormones. For example, the circadian rhythm boosts cortisol levels in the morning to wake you up, while producing melatonin in the evening to prepare you for sleep. However, in addition to having a circadian rhythm, women have a second body clock: the infradian rhythm.


What is the infradian rhythm and why should we care?

The infradian rhythm is a 28-day clock that starts with the first menstruation at puberty and ends with the last menstruation before menopause, thus impacting women for almost half of their lives.

The infradian rhythm has 4 different phases, each bringing important fluctuations in women’s bodies and brains. Research suggests that female brain chemistry can vary up to 25% over these 28 days. The table below summarizes each phase and key hormonal changes.

Given the centrality of hormones in regulating the body, it is not surprising that the infradian rhythm impacts the six pillars of brain health. However, since women’s hormones fluctuate with each phase, their effect on the six pillars will vary accordingly.

So how does the infradian rhythm impact the six pillars of brain health?


Physical Exercise

Rising estrogen and testosterone in the first half of the cycle contribute to increased physical energy, while the predominance of progesterone in the second half promotes more rest and relaxation.


Food and Nutrition

Studies show that women’s appetite and metabolism decrease in the first half of their cycle and increase in the second half. A study by Johnson et al. concluded that “variations in energy and fat intake over the menstrual cycle were not attributable to differences in energy expenditure through exercise or dietary restraint, and appear to be related to changes in the estrogen/progesterone ratio”.


Medical health

Hormonal imbalances have important effects on various medical health conditions. For example, women are five to eight times more prone to thyroid issues than men. Additionally, a 2012 study found that some female participants suffered from more acute autoimmune symptoms right before or during menstruation.


Sleep and relaxation

Balanced hormones facilitate better sleep and relaxation. Studies suggest that estrogen has a boosting effect on serotonin, also known as the ‘happiness hormone’, which both improves mood and promotes sleep. In the second half of the cycle, studies indicate that progesterone facilitates relaxation and sleep.


Mental fitness

Rising estrogen in the first half of the cycle increases synaptic connections in the hippocampus part of the brain, promoting communication, creativity, and mental acuity. During the second half, rising progesterone turns women’s energy inwards, promoting more rest and task completion. Healthy and balanced hormones are an essential component of mental fitness. Indeed, brain disorders such as migraines, schizophrenia, and traumatic brain injury are directly affected by hormonal fluctuations when imbalances occur.


Social interactions  

Our predisposition to social interactions are also impacted by our hormones. By enhancing the secretion of serotonin and increasing synaptic connections in the hippocampus, rising estrogen promotes communication skills and makes women more prone to socializing in the first half of their cycle. The second half of the cycle would then be more apt to promoting rest and self-care.



Final thoughts

Understanding the impact of the infradian rhythm on the six pillars of brain health can enable women to optimize their lifestyle in a way that best supports their natural ebbs and flows, as well as help the medical community address some long-standing health issues that disproportionately affect women.

While the current research offers exciting first steps, more long-term studies need to be conducted to fully understand the impact of female hormones on short and long-term health topics, from weight loss to Alzheimer’s. Since most medical research has been conducted on male humans and animals, it is essential to push for greater representation of females in their fertile years and in different phases of the menstrual cycle to get a more precise and complete picture. These are some of the policy changes the Women’s Brain Project is championing.

Find out more about everyday practical tips to invest in your brain health as a woman, backed by scientific evidence, here.

Maria-Theresa Sanchez is a recent graduate of the London School of Economics and Political Science, where she completed a Master’s in Public Administration with a focus on social impact. She is passionate about the intersection between mental health and environmental issues, as well as promoting female empowerment.

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