BACKGROUND: Most studies of immune dysregulation in perinatal mood and anxiety disorders have focused on peripheral cytokines, but literature from non-perinatal mood disorders also implicates T-cell defects. We sought to characterize proportions of T-cell subtypes in women with postpartum depression.

MATERIALS AND METHODS: We enrolled 21 women with postpartum depression (PPD), 39 healthy postpartum controls, and 114 healthy non-postpartum women. Blood was collected in sodium-heparin EDTA tubes and was analyzed using flow cytometry. We conducted statistical tests including linear regression analysis that were aimed at determining differences in proportions of T cell populations among groups.

RESULTS: Mean counts of T-cells (all CD3+ T cells), T-helper cells, (CD3+CD4+ T cells), and T-cytotoxic cells (CD3+CD8+ T cells) were significantly increased in healthy postpartum women compared to healthy non-postpartum controls (p < 0.001, p = 0.007, and p = 0.002, respectively), but not in women with PPD. The increases in healthy postpartum women were driven by increases in TH1 cells and T regulatory cells, increases that were nonexistent or attenuated in women with postpartum depression. Mean counts of CD4+ T-helper memory cells were also increased in healthy postpartum women (p = 0.009), but slightly decreased in women with PPD (p = 0.066), when compared to healthy non-postpartum controls.

CONCLUSIONS: Our study confirms that the postpartum period in healthy women is a time of enhanced T cell activity. Women with postpartum depression failed to show physiological enhanced T-cell activity postpartum, and future research is needed to elucidate etiological mechanisms and consequences.