467. THE NEUROANATOMY OF POSTPARTUM DEPRESSION: INSIGHTS FROM A CROSS-SECTIONAL STRUCTURAL MRI STUDY

Abstract Background Growing evidence suggests that the perinatal period is marked by significant neuroplasticity. Structural MRI studies report that healthy mothers exhibit lower grey matter volume (GMV) compared to healthy nulliparous women, even two years postpartum. However, evidence on the neural underpinnings of postpartum depression (PPD) remains inconclusive, with only a few studies investigating GMV changes in PPD. Aims & Objectives The present study aims to investigate GMV differences among healthy nulliparous women, healthy mothers, and mothers with PPD and how these correlate with mother-infant bonding, depressive symptomatology and maternal self-confidence measures. Method The sample included n = 20 healthy nulliparous women, n = 32 healthy mothers (0-18 months postpartum), and n = 18 mothers with PPD (0-18 months postpartum), who underwent 3T or 1.5T MRI scans. Mother-infant bonding was evaluated in both groups of mothers using the Postpartum Bonding Questionnaire (PBQ). Additionally, mothers with PPD completed the Edinburgh Postnatal Depression Scale (EPDS) and the Lips Maternal Self-Confidence Scale (LMSCS). Twelve regions of interest (ROIs) were selected based on previous literature and analysed for GMV using a customised pipeline implemented in FSL. Cross-sectional ANCOVAs and partial correlation analyses were carried out in Jamovi. Age and scanner type were included as covariates in all analyses, EPDS scores when relevant. Findings were considered significant if they survived false discovery rate (FDR) correction. Results ANCOVAs revealed significant differences among the three groups in the mean GMV of the amygdala (p < 0.001, η²p = 0.401), thalamus (p < 0.001, η²p = 0.314), globus pallidus (p < 0.001, η²p = 0.212), inferior frontal gyrus (p < 0.001, η²p = 0.372) and superior frontal gyrus (p < 0.001, η²p = 0.653). Post-hoc Tukey HSD tests revealed that healthy mothers displayed significantly lower GMV than healthy nulliparous women in the amygdala. In contrast, mothers with PPD showed significantly higher GMV than healthy mothers in the amygdala, thalamus, globus pallidus, inferior and superior frontal gyri, and higher GMV than healthy nulliparous women in the inferior and superior frontal gyri. Additionally, mothers with PPD displayed significantly higher PBQ scores than healthy mothers (p < 0.001, η²p = 0.380). However, no significant correlations were observed between regional GMV and PBQ scores in either group of mothers, nor between GMV and EPDS scores in mothers with PPD. Notably, right insular GMV positively correlated with LMSCS scores (r = 0.818, p = 0.002) in mothers with PPD. Discussion & Conclusions In conclusion, these results suggest that the postpartum period is marked by significant neuroplasticity. While healthy motherhood has been associated with GMV reductions, mothers with PPD appear to display an opposite pattern of GMV increases, especially in brain regions involved in the pleasure and reward networks. These findings highlight the potential neuroanatomical biomarkers of PPD, which could inform its early detection and treatment strategies.