With all the mixed messages about mercury exposure from fish and its impact on the brain development of the fetus, many pregnant women may be hesitant to eat a diet rich in fish.
But this study by National Institutes of Health and University of Illinois-Chicago researchers found pregnant women who had a deficient intake of omega-3 acids had double the risk of depression than women with a normal to high intake.
"During pregnancy, the baby gets omega-3 at the expense of the mother," explains study co-author Dr. John Davis, a professor of psychiatry at the University of Illinois-Chicago. He presented the research May 20 at the American Psychiatry Association's annual meeting in San Francisco.
A developing fetus draws on the fatty acid stores of its mother for optimal neurological growth. The study sought to determine if women are at the greatest risk for depression in the third trimester, when their rate of omega-3 depletion is the greatest.
Using British data compiled from 14,541 women who were expected to deliver between 1991 and 1992, the researchers used a statistical model to analyze the association between omega-3 fatty acids and depression.
The subjects' omega-3 intake was recorded at 32 weeks' gestation and was compared to the mothers' scores on a standardized depression test given at 18 and 32 weeks' gestation and again at eight and 32 weeks after birth.
Even after the researchers adjusted the data for confounding factors such as age, prior history of depression, education and substance abuse, the association remained strong.
Their findings were supported by an additional analysis, which showed that in countries where omega-3 intake is the highest, the incidence of depression appears to be the lowest.
"We suspect that too little omega-3 in the diet may be a risk factor for depression," Davis says.
However, a clinical trial where subjects with different intakes of omega-3 are randomly assigned to comparison groups is needed to draw any conclusions about the relationship between these fatty acids and depression, Davis says.
"The results are consistent with prior epidemiological work and consistent with more recent clinical trial work," says Dr. Andrew Stoll, an assistant professor of psychiatry at Harvard University.
Among the reasons many people may be deficient in omega-3 fatty acid is because it's available in just a handful of foods and because the body can't produce it on its own. According to Stoll, fatty cold-water fish such as salmon and omega-3 supplemented eggs are excellent sources of the healthful nutrient.
Learn about depression from the National Institute of Mental Health, while you can get more about nutrition and pregnancy from the American College of Obstetricians and Gynecologists.