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Fewer hours of daylight could lead to increased risk of postpartum depression

Researchers say women in their third trimester should be mindful of getting enough natural light

Photo (c) monkeybusinessimages - Getty Images
In a new study published in Springer, researchers found that women who are in their last trimester of pregnancy during the darker months of the year -- and are thus seeing fewer daylight hours -- are more likely to experience postpartum depression both during the last trimester and after their babies are born.

Some previous research has linked lack of natural light to depression in adults, but the complete breadth of research has been far from conclusive. Nevertheless, researcher Deepika Goyal and her team from the University of San Francisco conducted a sleep trial to provide further evidence.

The trial consisted of 293 women -- all first-time mothers and all from California -- both before and after pregnancy.

“Among first-time mothers, the length of day in the third trimester, specifically day lengths that are shortening compared to day lengths that are short, long, or lengthening, were associated with concurrent depressive symptom severity,” said Goyal, lead researcher of the study out of San Jose State University.

Need for natural light

The researchers used the daylight hours in the northern hemisphere. In this system, “shortening days” run from August 5 through November 4; “short days” last from November 5 through February 4; and “lengthening days” ran from February 5 to May 4; and “long days” are May 6 through August 4.

With those guidelines, the study found that the women whose third trimester consisted of more “short days” experienced the most depression symptoms at 35 percent. Once the babies were born, the researchers found the depression symptoms peaked.

Conversely, for those women whose final trimester was during months with longer daylight hours, the depression risk was at its lowest (26 percent). The study also found 30 percent of all participants to be at risk for developing depression.

When conducting the trials, the researchers evaluated risk factors associated with depression, such as how long each woman slept, history of depression, socioeconomic status, age, and recorded daylight hours during the final trimester.

Getting creative with light exposure

The researchers found that women who are exposed to more natural light in their final months of pregnancy -- and immediately following childbirth -- posed less of a risk for developing depression-related symptoms.

However, for women who have a history of mental health problems, have experienced symptoms of depression, or whose final months of pregnancy are during months with fewer daylight hours, the researchers suggest a number of different solutions to help with risks of depression.

“Women should be encouraged to get frequent exposure to daylight throughout their pregnancies to enhance their vitamin D levels and to suppress the hormone melatonin,” Goyal said. “Daily walks during daylight hours may be more effective in improving mood than walking inside a shopping mall or using a treadmill in a gym.”

Goyal also encourages utilizing light boxes -- a popular method used for light therapy -- and spending as much time outside as possible.

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