About 10% to 15% of women in the US have postpartum depression (PPD)—but that estimate is based mostly on women of European ancestry. In black women the rates are doubled, and among Latinas the prevalence is 30% to 43%. But those 2 groups have been inadequately studied, say researchers from University of North Carolina. To help remedy the lack of information, they conducted a study with the largest and “most robustly phenotyped” cohort of minority women with PPD. Their study also is the first to examine genetic ancestry as it contributes to PPD risk.
The researchers recruited 549 women with PPD and 968 without PPD who were within 6 weeks of having given birth. Of those, 67.4% were black, 14.4% were Latina, and 18.2% were white. The median age was 26.7; nearly half of the participants were married. Only 3.6% had given birth for the first time.
The women completed a battery of tests, including the Abuse and Trauma Inventory, Everyday Stressors Index (ESI), Edinburgh Postnatal Depression Scale (EPDS), and Postpartum Bonding Questionnaire. The researchers also assessed estradiol, progesterone, brain-derived neurotrophic factor, oxytocin, and allopregnanolone.
The women with PPD had significantly higher rates of previous psychiatric diagnoses, significantly higher EPDS total scores, and higher rates of family history of PPD. They also had significantly higher rates of previous diagnoses of major depressive disorder (MDD) (53% vs 15%), although 47% were experiencing their first episode of MDD. Dramatically higher numbers of women with PPD vs without PPD had suicidal thoughts in the month prior to assessment: 36% vs 2%, respectively.
Genetic ancestry was not predictive of case status, nor were hormonal influences any different between the 2 groups. Instead, psychiatric history and exposure to adverse life events were significant predictors. Nearly half of all the women with PPD had a lifetime anxiety disorder diagnosis compared with 7% of the controls. And although 67% of all participants reported a history of ≥ 1 traumatic event, women with PPD had double the proportion of multiple events of abuse and trauma. Women who had experienced multiple adverse life events were 3 times more likely to have PPD. Childhood and adult sexual abuse and life-threatening attack were among the most predictive.
The women with PPD had an ESI score > 3 times higher than that of the controls (19% vs 6%, respectively). The researchers note that cumulative lifetime stress may lead to epigenetic modification, and thus to PPD. Women with PPD also had a significantly higher proportion of dysfunctional mother-infant relationships, although the numbers were low in both groups (7% vs 0.35%, respectively).
The researchers say that although genetic ancestry did not play a role in determining case status, there are important ethnic and cultural differences that do play a role in treatment. For instance, Latinas and black women may be less likely to accept antidepressants as therapy. And because socioeconomic status is a determinant of health care access, they also face major barriers to mental health care. However, neither insurance nor education status (markers of socioeconomic status) distinguished cases from controls, even when the researchers controlled for genetic ancestry.