Genetical effects of sleep traits on postpartum depression: a bidirectional two-sample Mendelian randomization study

Postpartum depression (PPD) is widely recognized as the most prevalent mental health crisis following childbirth and has been linked to sleep disturbances. However, the potential causal relationships between various sleep traits and PPD remain unclear. This study employs a bidirectional two-sample Mendelian randomization (MR) approach to investigate these associations. The inverse-variance-weighted method was used to evaluate the causally linked sleep traits on postpartum depression. The weighted median, weighted mode, and MR-Egger were used to estimate the robustness of the inverse-variance-weighted method. The leave-one-out method estimated the sensitivity of the result. Cochran's Q method was used for the heterogeneous test. The MR-Egger intercept and MR-PRESSO methods detected the horizontal pleiotropy. We examined the genetic causal relationships between nine sleep traits and postpartum depression. Sleep apnea syndrome (OR: 1.122; 95%CI: 1.063-1.185; p = 0.000), sleeplessness/insomnia (OR: 1.465; 95%CI: 1.104-1.943; p = 0.008), and frequency of tiredness/lethargy in last 2 weeks (OR: 1.725; 95%CI: 1.345-2.213; p = 0.000) genetically predicted the increased risk of postpartum depression. The reverse Mendelian randomization analysis showed PPD caused sleeplessness/insomnia (β: 0.006; 95%CI: 0.001-0.010; p = 0.016) and frequency of tiredness/lethargy in last 2 weeks (β: 0.007; 95%CI: 0.002-0.011; p = 0.004). The remaining six sleep traits showed no significant association with PPD. There was no heterogeneity or horizontal pleiotropy. Genetic evidence reveals causal relationships between specific sleep traits and PPD, including sleep apnea syndrome, sleeplessness/insomnia, and tiredness. Whether certain sleep health indicators suggest a risk of postpartum depression or sleep issues that are caused by PPD, both may offer insights into the prevention and treatment of PPD.