Low Breast Milk DHA Linked to Greater Risk of Depressive Symptoms in Pregnancy

One of the more pressing questions about perinatal depressive symptoms is why some women develop the condition and others do not. A history of depressive illness, high levels of stress and adverse socioeconomic conditions increase the risk of a woman’s developing depressive symptoms, but other factors also contribute to the risk. One of these may be a woman’s long-chain PUFA status, especially her blood and tissue concentrations of DHA. This fatty acid is especially important during pregnancy because maternal diet and stores supply DHA for fetal and infant brain development. Women supplemented with DHA during pregnancy have higher DHA status during pregnancy and a lower rate of DHA loss in the third trimester compared with unsupplemented women.

Low DHA concentrations in maternal plasma or red blood cells are associated with major depressive symptoms and low brain DHA concentrations. Although not all studies have reported low levels of DHA in depressed patients, the observation has been reported repeatedly. Observational data suggest that populations with high intakes of fish and seafood have lower rates of depressive illness than those who eat little seafood. The involvement of DHA in neuronal membranes, cell signaling, neurotransmission and hormonal responses provides a plausible basis for considering the likelihood of a functional link between DHA in brain and depressive symptoms.

Some intervention studies have been conducted with long-chain omega-3 PUFAs (n-3 LC-PUFAs) or fish oil and perinatal depressive illness, but data are inconsistent. Evidence suggests that major depressive episodes occur more frequently postpartum than during pregnancy. A recent review found “limited evidence” of an association between postpartum depressive symptoms and dietary intakes of n-3 PUFAs and fish during pregnancy. It may be surprising that until now investigators have not questioned whether there is a relationship between depressive symptoms during pregnancy and breast milk fatty acid concentrations. Sarah Keim and colleagues at the University of North Carolina, U.S., examined this relationship using assessments of depressive symptoms recorded at 2 times during pregnancy in a cohort of 2,006 women participating in the longitudinal Pregnancy, Infection and Nutrition (PIN) study. Participants were recruited at < 20 weeks’ gestation from the University of North Carolina prenatal care clinics. Characteristics of the participants have been described elsewhere.

The postpartum component of the study included follow-up visits with the participants at 3 and 12 months postpartum. From the original cohort, 689 women completed the 3-month in-home interview. Of the mothers who were breastfeeding in the fourth postpartum month, 305 provided a sample of breast milk and 287 had complete fatty acid data plus depressive symptom assessments. The investigators used the Center for Epidemiologic Studies Depression Scale (CES-D Scale) to assess the mothers’ depressive symptoms before 20 weeks and at 24-29 weeks’ gestation. Higher scores indicate more severe symptoms with a score of 16+ suggesting a high level of symptoms.

For assessment at < 20 weeks’ gestation, 12% of women had depressive symptom scores of 16+ or higher; at 24 to 29 weeks’ gestation, the proportion was 16%. These prevalences are at the higher end of some estimates for perinatal depressive symptoms in US women, but not others. Higher scores were significantly associated with fewer years of education, smoking, lower income and younger maternal age (17 to 20 years). The median intake of total n-3 PUFAs was just 0.42 g/day, but consumption of these fatty acids was unrelated to depressive symptom scores.

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Breast milk DHA concentrations after 3 months postpartum were higher in women with more than 16 years’ education (median 0.25%, interquartile range, 0.25) compared with those having up to 12 years’ education (median 0.14%, interquartile range, 0.09). These data are half the average breast milk DHA concentration of 0.32% worldwide and suggest that less educated women in particular are at high risk for inadequate levels of breast milk DHA. Other reports have documented low breast milk DHA concentrations in American women.

Depressive symptoms at < 20 weeks’ gestation were inversely associated with breast milk DHA concentrations in analysis adjusted for education, smoking, maternal age, parity, income and dietary n-3 or n-6 PUFAs, but the association was not significant for depressive symptoms assessed at 24 to 29 weeks’ gestation. Depressive symptoms were not associated with EPA, n-6 PUFAs or the ratio of n-6:n-3 PUFAs.

The authors raise the intriguing possibility that women who present symptoms early in pregnancy may be more likely to have chronic depressive symptoms, whereas those whose symptoms occur later in pregnancy may include those with chronic depression plus women whose symptoms might be triggered by hormonal stress and psychosocial factors associated with pregnancy. There is some support for this idea from Australian women with chronic depression prior to pregnancy who also had low blood concentrations of n-3 PUFAs. Confirming the lack of association between later onset symptoms and breast milk DHA concentrations probably requires a larger sample. The possibility that depressive symptoms lead to or reinforce poorer dietary habits and low n-3 PUFA intakes is another consideration.

This study adds to the substantial evidence that DHA concentrations in pregnant US women are low, particularly among women with less education attainment. It suggests a link between low maternal DHA status in blood and breast milk and a greater risk of depressive symptoms in early pregnancy, before 20 weeks’ gestation. These observations further imply that low breast milk DHA concentrations may be associated with suboptimal brain and visual development in the offspring. Improving the DHA status of women during and after pregnancy seems prudent and urgent.Keim SA, Daniels JL, Siega-Riz AM, Dole N, Herring AH, Scheidt PC. Depressive symptoms during pregnancy and the concentration of fatty acids in breast milk. J Hum Lact 2012; Jan. 4. [Epub ahead of print] PubMed