Table 1. A summary of systematic reviews of risk factors for postpartum depression.

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Risk factor	Findings	Study designs
Social relationships	Low spousal and social support were implicated as risk factors for PPD.	Five longitudinal studies, three cross-sectional studies, and one qualitative in-depth interview were conducted.
Past history of depression and lack of support	Most studies show an elevated odds ratio between lack of support and past depression and the occurrence of PPD.	Two RCTs; one population-based survey; one telephonic survey; one minority patient chart review; one prospective longitudinal study; one systematic review and one meta-analysis.
Immigration status	Higher levels of acculturation were reported by five studies as a risk factor for PPD.	Four cross-sectional studies and three longitudinal studies
Genetic and epigenetic markers	The studies analyzed and outlined associations between postpartum depression and epigenetic marker modifications, SNPs, and deletion or insertion polymorphisms.	37 studies
Chronic illness	Not much evidence was found.	Four studies
Vitamin D	Out of the nine studies, five showed a positive correlation between vitamin D in pregnancy and PPD, while the others showed no correlation.	Six prospective studies; four cross-sectional studies; two prospective secondary analyses; one RCT; one case-control study
Cesarean section	PPD levels did not differ significantly between women who had an emergency cesarean section and those who had a normal vaginal delivery.	Three cohorts
Abuse	PPD was higher among those with past or current abuse as well as those with substance abuse disorders.	Eight designs
Diabetes	In both PPD and depression in pregnancy, diabetes was a risk factor.	15 observational retrospective designs were described, 30 prospective observational designs were described, and three RCTs were described.
Body image dissatisfaction	A consistent but weak association was found.	Nine prospective cohorts, 10 cross-sectional studies
Multiple births	Higher levels of PPD were seen.	Seven studies
Women’s birth experiences	11 studies demonstrated an increase in the occurrence of PPD in women with negative birth experiences.	Five studies were retrospective; five were secondary analyses of previously collected data; and five were prospective.
Pre-pregnancy obesity	Two studies reported a positive correlation, while one reported no association.	Pre-pregnancy obesity
Women with preterm and low-birth-weight infants	About 40% of women with preterm deliveries develop PPD early in the postpartum period. Women with LBW babies have a higher risk of developing PPD till a year after delivery.	26 studies