In addition, for women of children born in the autumn or winter who have never been depressed or had other psychological problems, the risk is three times as great compared with women who become mothers in the spring months.
“Our results indicate that women who have children during the last three months of the year ought to have more thorough follow ups in order to identify and offer support to those who show signs of depression,” doctor and researcher Sara Sylvén from Uppsala University Hospital’s maternity clinic told the local Upsala Nya Tidning (UNT) newspaper.
The findings are based on a study of around 2,000 new mothers in Uppsala County in eastern Sweden which asked new mothers to take a survey on three occasions after giving birth – five days, six weeks, and six months.
The survey included a number of questions commonly used to detect depression.
Overall, the results revealed that approximately one in ten new mothers suffered from postnatal depression both six weeks and six months after giving birth.
However, among women who gave birth in October, November, and December, the tendency was substantially higher, while “only” one in twelve women who gave birth in April, May, or June showed signs of depression.
The study did not examine what may lie behind the different depression risks.
“We do know, however, that sunlight and darkness affect a number of signal substances and hormones which can have ties to depression,” said Sylvén, who added that she and her team planned to investigated the causes of the increased depression risk in future studies.