The reproductive hormone cycle for those assigned female at birth consists of phases which can yield daily-life changes for both one’s physicality and mental state. The phases include: the menses (bleeding period), follicular phase, ovulation, and luteal phase.

When studying mood disorders, understanding this cycle is crucial. As the hormone levels spike, peak, and drop throughout the entirety of the menstrual cycle, an individual can experience a variety of symptoms, including (but not limited to) low mood, trouble focusing, and depleted energy. Studies on mood disorders tend to neglect the impact of the menstrual cycle on these symptoms, which may also be characteristics of mood disorders, making it difficult to get a full grasp on a treatment’s efficacy or a study’s generalizability — particularly for those who menstruate.