How Sleep, Mental Health, and Menstrual Cycles Are Deeply Connected

A new study has uncovered a strong link between women's mental health, sleep patterns, and menstrual cycles. Led by Assoc. Prof. Jihwan Myung, the research shows how disrupted circadian rhythms and mood-stabilising drugs can alter reproductive cycles. The findings were published in Chronobiology in Medicine in June 2025 and could lead to more tailored treatments for mood disorders in women.

The brain's internal clock, located in the hypothalamus, does more than regulate daily rhythms—it also interacts with reproductive systems that follow monthly cycles. This connection means that disruptions to sleep, such as shift work, jet lag, or irregular schedules, can directly affect menstrual regularity. The study found that artificial light exposure and mood stabilisers like lithium further complicate this relationship by lengthening circadian rhythms and disturbing hormonal balance.

Millions of women already experience irregular periods due to these factors, which can also worsen conditions like depression and bipolar disorder. The research highlights that seasonal changes play a role too: shorter daylight in winter tends to lengthen reproductive cycles, while longer daylight in summer shortens them. This sensitivity suggests that internal biological systems respond not just to daily cues but also to broader environmental shifts. By combining human and animal data, the study demonstrates how mood-stabilising medications interfere with hormonal rhythms. The findings push for future medical models that consider multiple timescales—daily, monthly, and seasonal—to better manage these effects without compromising mental or reproductive health.

The research underscores the need for treatments that account for the interplay between circadian rhythms and reproductive health. Women with mood disorders may benefit from more personalised approaches that consider their hormonal cycles alongside mental health needs. The study's insights could help refine therapies, reducing side effects on both sleep and menstruation.