Relationship between age at sexual debut and postpartum depression: a two-sample Mendelian randomization study

Engaging in sexual activity prematurely can lead to adverse emotional consequences for women. Current observational study suggests that such behavior may increase self-esteem sensitivity and trigger heightened feelings of remorse among adolescent girls. Additionally, insufficient contraceptive measures after sexual activity could potentially result in pregnancy and childbirth. Nevertheless, there is a noticeable lack of focused research on the significant reproductive issue of a potential connection between early sexual activity and postpartum depression in females. To address this gap, we have conducted a Mendelian randomization analysis, using the initiation of sexual activity as the exposure variable and postpartum depression as the outcome variable.

Using genome-wide association studies (GWAS) summary data that includes information from 194,174 samples regarding the age at first sexual intercourse, as well as GWAS summary data involving 231,644 samples for postpartum depression, and employing methods such as CAUSE, the inverse variance weighting method, MR-Egger, MR-PRESSO, and similar approaches, we conducted a Mendelian randomization analysis to investigate the potential relationship between the age at first sexual intercourse and postpartum depression. To validate the robustness of our findings derived from methods using genome-wide significant loci, we also conducted various sensitivity analyses.

The findings revealed that the age at which individuals initiated their first sexual intercourse exhibited a negative correlation with vulnerability to postpartum depression. To clarify, for each additional year in the age of first sexual intercourse, the susceptibility to postpartum depression decreased by 11.3% (OR, 0.887; 95% CI, 0.852-0.932; p = 0.013). Additionally, when applying the inverse variance weighting (IVW) method, we also discovered an association between the age at first sexual intercourse and postpartum depression (OR, 0.859; 95% CI, 0.771-0.957; p = 0.0060). Furthermore, the final IVW model did not reveal any evidence of horizontal pleiotropy or heterogeneity, suggesting that our results may support a potential causal relationship.

A deferred age of initial sexual intercourse enhances efforts to reduce the risk of postpartum depression in women. Hence, it might be a necessary to integrate this content into sex education aimed at adolescents.