Shared Genetic Architecture of Premenstrual Disorder and Postpartum Depression: Registry-Based and Genetic Evidence
Background Premenstrual disorder (PMD) and postpartum depression (PPD) have a strong phenotypic link and echo women’s hormone fluctuations. Yet, the extent to which they may be cross-inherited remains poorly understood. Methods Using the nationwide cohort of 907,841 women who born 1950-2007 and gave birth during 2001-2021 in Sweden, we estimated the cumulative incidence functions-based heritability and genetic correlation for PMD and PPD. We also analyzed genome-wide association study (GWAS) summary statistics from the largest European-ancestry cohorts for PMD (17,511 cases and 54,786 controls) and PPD (16,145 cases and 46,609 controls) using linkage disequilibrium score regression (LDSC). Fixed-effect cross-trait meta-analysis and imputed transcriptome-wide association analyses (TWAS) were conducted to identify shared loci and gene-tissue associations. Results The register-based heritability was 0.35 (95% CI: 0.29-0.41) for PMD and 0.31 (95% CI: 0.23-0.37) for PPD, with a positive genetic correlation between these disorders (rg = 0.47, 95% CI: 0.25–0.69). LDSC also showed a positive genetic correlation between PMD and PPD (rg = 0.66, SE = 0.10, P = 1.014×10−10), indicating sizable shared heritable influences. Cross-trait meta-analysis identified two novel genome-wide significant loci jointly associated with PMD and PPD, mapping to an intronic region of PCDH9 and the 3’ untranslated region of KCTD16. The KCTD16 locus implicates GABAB–mediated inhibitory signaling in both disorders. Consistent with this, TWAS revealed a hippocampus regulatory signal for KCTD16, with no detectable trend effects in other brain regions or peripheral tissues. Beyond the lead loci, TWAS suggested that the shared risk variants may partially act through genetically regulated gene expression across brain, endocrine and immune-related tissues. Conclusions Together, these findings provide the first evidence for sizable genetic overlap between PMD and PPD and highlight novel and convergent biological mechanisms underlying the abnormal brain response of some women to gonadal hormone fluctuations.