Study: Post-Partum Depression More Likely in Winter

SUNDAY, Oct. 14, 2018 -- Women whose final stages of pregnancy occur during the short, dark days of winter may be at increased risk for postpartum depression, a new study suggests.

It has to do with reduced exposure to sunlight -- the same culprit that contributes to seasonal affective disorder, or SAD. That's a type of depression that usually starts in fall and winter and disappears in spring and summer. 

The study authors said their findings should prompt doctors to encourage pregnant women who are at high risk for postpartum depression to increase their exposure to daylight and boost their levels of vitamin D.

The study was led by Deepika Goyal, a professor of nursing at San Jose StateUniversity. She and her team reviewed data on nearly 300 first-time mothers who took part in randomized controlled sleep trials before and after pregnancy. 

The researchers looked at the amount of daylight during the women's last trimester of pregnancy and other risk factors for postpartum depression, such as medical history, age, socioeconomic status and sleep quality.

Overall, participants had a 30 percent risk for depression. Their odds were strongly influenced by the number of daylight hours during the last month of pregnancy and immediately after delivery.

Women who were in the late stages of pregnancy during winter had a 35 percent risk -- the highest scores -- for postpartum depression. And their symptoms were more severe, the study found.

Women whose third trimester coincided with longer hours of daylight had a 26 percent risk for depression, the study showed.

"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," Goyal said.

The study was published recently in a special issue of the Journal of Behavioral Medicine focused on postpartum health.