A dip in libido is observed in women during a specific phase of their menstrual cycle. Experts from the University of California suggest this is not by chance. Their findings were published on the resource sciencedirect.com.
A team of American researchers concluded that this period corresponds to the interval from the fifth to the ninth day following ovulation. This timeframe offers the highest probability for a fertilized egg to successfully implant into the uterine lining. During this time, the endometrium temporarily suppresses its immune response to prevent the body from attacking the embryo as a foreign entity. However, this reduction in immunity leaves the reproductive tract more susceptible to infections, including those transmitted sexually.
The authors proposed an evolutionary hypothesis: a psychological mechanism might have developed to specifically diminish sexual desire during this vulnerable phase, thereby mitigating the risk of infection when bodily defenses are lowered. To test this idea, the specialists analyzed data from three diary studies conducted in the laboratory.
The analysis encompassed over 2,500 daily observations of female university students not utilizing hormonal contraception. Participants completed online questionnaires each morning, rating their level of sexual desire over the preceding day on a seven-point scale, and also noting whether they had engaged in masturbation. Cycle phases were determined using biomarkers: tests for luteinizing hormone in urine or analysis of salivary hormones.
The results proved consistent across all samples. During the implantation window, women most frequently reported very low levels of sexual desire compared to other cycle phases. Furthermore, the likelihood of masturbation at this time also dropped by approximately one-third.
Crucially, the effect remained similar even when compared to non-menstruating days, indicating that the decrease cannot solely be attributed to discomfort associated with menstrual bleeding. The reduction applied to sexual interest broadly, encompassing desire directed toward a steady partner as well as interest in new partners.
It has previously been established that sexual attraction intensifies near ovulation, the time when conception becomes most likely. This new research points to a corresponding decrease in motivation in the latter half of the cycle, which coincides with the period of peak vulnerability to infections.
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