Effects of menstrual cycle phase on interoception: A daily experience sampling study across two cycles
This study provides the first evidence that interoceptive accuracy and attention vary across the menstrual cycle in females, with accuracy peaking during the periovulatory phase and attention driven by physical symptom burden during the perimenstrual phase, suggesting hormonal fluctuations contribute to sex differences in interoception.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
The human body is constantly sending a quiet stream of signals from the inside out: the rhythm of a heartbeat, the ache of hunger, the tightness of a muscle. The brain's ability to sense and interpret these internal messages is called interoception. While we often think of our senses as tools for navigating the outside world—seeing a tree or hearing a song—interoception is the sense that keeps us tuned to our own physical state. Scientists have long noticed that women, on average, report paying more attention to these internal signals and sometimes struggle more with accurately counting their heartbeats in laboratory tests than men do. This difference has been linked to higher rates of anxiety and depression in women, yet the reason for this gap has remained a mystery. One leading theory suggests that the answer lies in the sheer amount of physical and hormonal change women experience throughout their lives, a constant shifting of the internal landscape that men do not face in the same way.
To test this idea, researchers set out to see if a woman's ability to sense her body changes as her hormones shift from week to week. They focused on the menstrual cycle, a natural monthly rhythm that causes significant fluctuations in hormones and physical sensations. Twenty women with regular cycles volunteered for a unique study that required them to track their bodies every single day for two full months. Instead of visiting a lab once, they used their smartphones to complete short tasks and answer questions right from their homes. Each day, they performed a specific exercise to test how well they could match a sound to their own heartbeat, a measure of accuracy. At the same time, they reported how much attention they were paying to their hunger, breathing, and other bodily feelings. To ensure the results were about internal sensing and not just general attention, they also completed a control task where they matched sounds to a flashing light on the screen, which had nothing to do with their bodies. The researchers also tracked their body temperature and cervical mucus daily to pinpoint exactly where they were in their cycle, confirming ovulation with the same precision used in fertility tracking.
The study revealed that the body's internal sense is not a fixed trait but a fluid state that changes with the cycle. When the researchers looked at the data from complete cycles, they found that women were significantly better at detecting their heartbeats during the periovulatory phase, the few days around when an egg is released, compared to the days when they were menstruating. This improvement in accuracy happened specifically for the internal task; their performance on the control task with the flashing light did not show the same pattern, suggesting the change was specific to how they processed their own body signals. The researchers also discovered that the timing of the data collection mattered. The clear patterns only emerged when the data was analyzed as a full, unbroken cycle. When the data was mixed together from different cycles, the signal became blurry, suggesting that the body's internal state is highly sensitive to the specific hormonal context of that particular month.
While accuracy peaked around ovulation, the women's attention to their bodies told a different story. The researchers found that women reported paying the most attention to their internal sensations during the days of their period. However, this heightened attention was not a mysterious shift in focus; it was directly explained by the physical symptoms they were experiencing. When the women reported more physical discomfort, such as cramps or headaches, their attention to their bodies increased. Once the researchers accounted for these symptoms, the difference in attention between the menstrual phase and other phases largely disappeared. This suggests that during the period, women are not suddenly more tuned in to their bodies for no reason; rather, the physical signals are simply louder and harder to ignore. Interestingly, when women did notice their internal signals, they tended to rate that attention as more positive and helpful during the ovulatory phase compared to other times, a subtle shift in how they felt about their own awareness.
These findings challenge the old idea that how we sense our bodies is a stable personality trait that stays the same from day to day. Instead, the study shows that interoception fluctuates significantly within the same person over the course of a month. This variability appears to be a normal part of being female, driven by the natural hormonal tides of the menstrual cycle. The results suggest that the differences often seen between men and women in how they sense their bodies may not be due to a fundamental difference in ability, but rather a reflection of the different levels of hormonal and physical change each sex experiences. By showing that a woman's internal sense can change depending on where she is in her cycle, the research offers a new way to understand why women might be more vulnerable to certain mental health conditions linked to body awareness. It implies that to truly understand the human mind and body, we must look at the whole cycle, not just a single snapshot in time.
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