Background Depression in the perinatal period, during pregnancy or within 1 year of childbirth, imposes a high burden on women with rippling effects through her and her child’s life course. Social support may be an important protective factor, but the complex bidirectional relationship with depression, alongside a paucity of longitudinal explorations, leaves much unknown about critical windows of social support exposure across the perinatal period and causal impacts on future depressive episodes.

Methods This study leverages marginal structural models to evaluate associations between longitudinal patterns of perinatal social support and subsequent maternal depression at 6 and 12 months postpartum. In a cohort of women in rural Pakistan (n=780), recruited in the third trimester of pregnancy and followed up at 3, 6 and 12 months postpartum, we assessed social support using two well-validated measures: the Multidimensional Scale of Perceived Social Support (MSPSS) and the Maternal Social Support Index (MSSI). Major depressive disorder was assessed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (DSM IV).

Results High and sustained scores on the MSPSS through the perinatal period were associated with a decreased risk of depression at 12 months postpartum (0.35, 95% CI: 0.19 to 0.63). Evidence suggests the recency of support also matters, but estimates are imprecise. We did not find evidence of a protective effect for support based on the MSSI.

Conclusions This study highlights the protective effect of sustained social support, particularly emotional support, on perinatal depression. Interventions targeting, leveraging and maintaining this type of support may be particularly important for reducing postpartum depression.