Disentangling direct and indirect genetic effects from partners and offspring on maternal depression using trio-GCTA

Maternal depressive symptoms are highly prevalent and can negatively impact affected individuals and family members. Understanding etiological influences on maternal depression, such as genetic liability, is key to inform treatment and prevention efforts. Here we quantified direct and indirect genetic effects (that is, when genetic variants in other individuals influence risk of maternal depression through the environment) from partners and offspring on maternal depressive symptoms at multiple time points using genome-wide complex trait analysis with parent–offspring trios. We used data from the Norwegian Mother, Father and Child cohort study, including up to 21,000 genotyped parent–offspring trios. Models with indirect genetic effects had best fit at three out of five time points (3, 5 and 8 years after birth). The variance in maternal depressive symptoms explained by direct genetic effects ranged from 5% to 14%, whereas indirect genetic effects explained 0–14% of variance across time points. Heritable traits in family members contribute to maternal depressive symptoms through the environment at several time points after birth.