In my career as a gynaecologist, I have often encountered some interesting phenomena, and one of them is the gradual synchronization of menstrual cycles between girlfriends. Once, in my clinic, two good friends visited at the same time, and they were similarly puzzled: Why did their menstrual cycles start to get closer and closer since moving to the same apartment, even almost on the same day?
Biological basis - the role of pheromones
The role of pheromones is a key factor in exploring the biological basis of the phenomenon of menstrual cycle synchronization between girlfriends. Pheromones are chemicals secreted by animals and humans that are able to transmit information through the olfactory system that affects the behavior and physiological state of other individuals. Between women, especially girlfriends who often live together or spend a lot of time together, pheromones may play an unconscious role in promoting the synchronization of menstrual cycles. This phenomenon was first observed in women's dormitories and work settings, and one of the obvious manifestations was the convergence of menstrual cycles.
Specifically, pheromones can affect the synchronization of the menstrual cycle through the following steps:
Release and sensing: The body releases pheromones through the skin and respiratory system. When two or more women are in close proximity, their bodies may absorb pheromones released by each other. Signal interpretation: When exposed to pheromones, the body's olfactory receptors – the olfactory bulb located in the nose – pick up these chemical signals and relay the information to the brain, especially the hypothalamus, which affects hormone production. Physiological response: When the brain receives a pheromone signal, it may adjust the production of hormones, especially hormones associated with the menstrual cycle, such as estrogen and progesterone. This adjustment has the potential to lead to a change in the menstrual cycle and eventually a synchronization of the cycle. Although this theory offers a possible explanation, the scientific community is still working on the mechanism of the specific action of pheromones on menstrual synchronization. However, this biological phenomenon highlights the complex interplay between human behavior and physiology, as well as the subtle ways in which information is exchanged in nature.
Psychosocial factors
Regarding the psychosocial factors in the gradual synchronization of menstrual cycles between girlfriends, we can delve into how emotional communication and shared life experiences may affect women's menstrual cycles. In close friendships, especially between women who live for a long time or spend a lot of time with each other, the emotional interaction is very frequent and deep. This interaction includes sharing personal stress, happiness, lifestyle habits, and even health conditions, among other things. The resonance of emotions and the sharing of experiences may invisibly affect the respective physiological states, including hormonal fluctuations. For example, if a woman shares with a friend when she experiences emotional stress or a happy event, her emotional response—whether anxious or excited—may affect her menstrual cycle through complex physiological pathways, such as changes in the endocrine system. When this emotional exchange occurs cyclically among friends, their physiological responses may also converge. In addition, the common living environment and work and rest habits are also a psychosocial factor that affects menstrual synchronization. Women who live together tend to synchronize eating habits, sleep patterns, and daily activities, all of which have been scientifically studied to be associated with the regularity and synchronization of menstrual cycles. In summary, psychosocial factors establish a potential physiological connection between friends through emotional resonance and a shared lifestyle, which may be a key factor in the synchronization of menstrual cycles. This phenomenon highlights the potential impact of interpersonal closeness on women's physical health.
Scientific controversy and research
Research supports the fact that in 1971, psychologist Marta McClintock first proposed in her study the synchronization of menstrual cycles between female roommates, which she called the "McClintock effect". McClintock observed that the menstrual cycles of the women who lived together tended to be consistent, which she attributed to the effects of pheromones sensed by the body's olfactory system. The study attracted a lot of attention in the years that followed, prompting other scientists to investigate the phenomenon as well. However, as research methods have improved and sample sizes have increased, more and more scientists have begun to question the effectiveness of menstrual synchronization. Some subsequent studies have failed to replicate McClintock's findings. For example, a large-scale study using more rigorous statistical methods and control variables showed that the observed phenomenon of menstrual synchronization may be merely a fortuitous event. In addition, the scientific community remains inconclusive about the specific role of pheromones in human behavior and physiological responses, which has heightened doubts about the scientific basis of the phenomenon of menstrual synchrony. Overall view: At present, the scientific evidence on menstrual synchronization is still mixed. Although there are some arguments and cons for this, most scientists believe that more high-quality research is needed to explore whether this phenomenon actually exists. In addition, researchers are also exploring other factors that may affect the menstrual cycle, such as environment, genetics, and lifestyle. In conclusion, the authenticity of menstrual synchronization as a scientific concept still needs further scientific verification. Future research in this area may provide a clearer answer.