Seasonal variation in postnatal depression

We evaluated the occurrence of postnatal depression in general and during different seasons as part of a larger longitudinal mother-child follow-up study.

One hundred and eighty-five mothers, from the maternity wards of University Hospital of Oulu, Finland, completed a self-rating depression scale, the Edinburgh Postnatal Depression Scale (EPDS) twice: first at hospital 2-7 days after delivery and the second time at home 4 months after the delivery. Different psychosocial variables were mapped out to avoid any confounding factors. The year was divided in two separate ways: first, three different time periods were selected by the amount of sunlight: dark (October-January), intermediate (February, March, August, September) and light (April-July), and second, the year was divided by seasons. The results were analysed by the chi(2)-test for multinomials.

Sixteen percent (16.2) of mothers were scored as being depressed using 13 as a cut-off point immediately after the infant was born. Thirteen percent (13.0) were depressed measured 4 months postpartum. There was more mild depression in the autumn (ratio observed/expected 1,62; 95% confidence interval 1.05-2.19) immediately after delivery, using 10 as a cut-off, and less depression in the spring (0.27; 0.00-0.62) measured at home later, using 13 as a cut-off. When using classification by the amount of light there was more depression during the dark time (1.58; 1.05-2.11) immediately postpartum.

The group sizes and the amount of sample sizes collected within each month are quite small.

It should be borne in mind that seasonal changes and alterations in the amount of light might influence the occurrence of postnatal depression.