Supplementary Material for: Higher depressive symptoms in irregular menstrual cycles - converging evidence from cross-sectional and prospective assessments

Background: Menstrual cycle regularity is an important marker of reproductive health and associated with physiological and psychological illnesses, as well as experiencing stress. We hypothesized that individuals with irregular menstrual cycles report higher depressive symptom severity, after controlling for stress occurrence.
Methods: The hypothesis was examined through two measurement approaches: a cross-sectional and a prospective, longitudinal study. In the cross-sectional study, participants (n = 394) reported depressive symptoms and their overall menstrual cycle regularity. In the longitudinal study, participants (n = 77) completed questionnaires on depressive symptoms and stress during the mid-follicular and periovulatory phase of one menstrual cycle. Depressive symptoms were compared between participants with regular and irregular cycles through a Welch t-test and an ANCOVA.
Results: Participants with irregular menstrual cycles reported more depressive symptoms in the cross-sectional analysis. Similarly, in the longitudinal analysis, the group with a current irregular menstrual cycle reported more depressive symptoms after controlling for stress occurrence. When including only complete data sets without multiple imputation (n = 52), the direction of the effects remained, but did not reach statistical significance.
Limitations: Although we investigated the menstrual cycle prospectively, it would have been more precise to include two or more cycles and daily sex hormone measurements. Further limitations were the suboptimal statistical power and the data collection during the COVID pandemic.
Conclusions: The results indicate an association between depressive symptoms and menstrual cycle irregularity. We give recommendations on how to incorporate this in future study designs on women’s mental health.

研究背景：月经周期规律性是生殖健康的重要标志，其与生理及心理疾病、压力体验密切相关。本研究提出假设：在控制压力发生情况后，月经周期不规律者报告的抑郁症状严重程度更高。
研究方法：本研究通过两种研究设计验证上述假设：横断面研究与前瞻性纵向研究。其中横断面研究纳入394名参与者，要求其报告抑郁症状及整体月经周期规律性；纵向研究则纳入77名参与者，要求其在一个月经周期的中卵泡期及围排卵期完成关于抑郁症状与压力的问卷调研。通过Welch t检验与协方差分析（ANCOVA），对比月经周期规律与不规律参与者的抑郁症状水平。
研究结果：横断面分析显示，月经周期不规律的参与者报告的抑郁症状更多。类似地，纵向分析结果表明，在控制压力发生情况后，当前月经周期不规律的组报告的抑郁症状水平更高。仅纳入未经过多重插补的完整数据集（n=52）时，效应方向保持一致，但未达到统计学显著性。
研究局限性：尽管本研究对月经周期进行了前瞻性调研，但纳入2个及以上月经周期并每日检测性激素水平将使研究更为精准。此外，本研究还存在统计效力不足、数据采集于新冠疫情期间等局限性。
研究结论：本研究结果证实抑郁症状与月经周期不规律存在关联。我们就如何将该结论应用于未来女性心理健康相关研究设计提出了建议。