The finding builds on previous research, which found maternal depression is more common four years after the birth of a first child than at any time in the first 12 months postpartum.
The new findings are the latest to come from the Maternal Health Study, which has been following over 1500 first time mothers from early pregnancy through the early parenting years.
Study participants completed questionnaires in early pregnancy, at three, six and 12 months postpartum and again when their first child was aged four.
Researchers found that children whose mothers reported depressive symptoms at four years postpartum had a threefold greater likelihood of experiencing emotional and behavioural problems compared to children whose mothers were not depressed at the time.
Researchers also found that women experiencing depressive symptoms during pregnancy and the postnatal period had a two and a half-fold increased chance of having four-year old offspring with emotional and behavioural issues. The same was true for women who experienced depression at any point in the first 12 months.
Dr Hannah Woolhouse said the results suggest that current systems of maternal health monitoring need to be extended to support women and children beyond the perinatal period.
“Our research challenges the assumption that the first months post pregnancy are the most critical in maternal health. While attention has always been focused on women’s health soon after birth, we now know that persisting or recurring depressive symptoms can also have impacts on family wellbeing.”
"This suggests a need to rethink how we’re offering maternal health services and primary care support, because women are vulnerable well beyond the first year postpartum, and so are their kids,” Dr Woolhouse said.
The findings add to growing evidence that persisting or recurrent maternal depression has more detrimental impacts on child outcomes when compared to a single episode of depression during pregnancy or soon after birth.
Australian clinical guidelines currently recommend screening for perinatal mental health disorders in early pregnancy and shortly after hospital discharge, most commonly in the first six to twelve weeks after birth.
“Many factors make women vulnerable to depression beyond this period,“ Dr Woolhouse said. “We are only just beginning to understand the extent to which the women’s and children’s health are linked. This has important implications for primary health care services, especially when depression is linked to factors such as family violence or social disadvantage."
The study was published in Archives of Women's Mental Health.