Children are more likely to develop behavioral or emotional problems if their mothers are chronically depressed, even if symptoms aren't severe, a French study finds. 

"There is a large group of mothers with depressive symptoms that are not severe enough to lead to a diagnosis, and who probably do not even seek help from their health care providers, but that do have a negative impact on their children's emotional and behavioral wellbeing," van der Waerden, a researcher at the French National Institute of Health and Medical Research in Paris, said by email.

Van der Waerden and colleagues followed more than 1,100 mother-child pairs in France from pregnancy through the children's fifth birthdays, periodically assessing maternal mental health as well as emotional and behavioral development of the kids.

Researchers questioned the children at age 5 to assess emotional symptoms, conduct problems, signs of hyperactivity or inattention, problems with peer relationships and social behavior.

In addition, researchers gave mothers questionnaires to measure depression symptoms during pregnancy and the first year of parenthood, as well as when the children were three and five years old.

Sixty-two percent of the mothers experienced no signs of depression during the study period and 4.6 percent had chronic, severe depression. About one in four had persistent moderate depression symptoms.

For some women, severe depression happened for a shorter period of time, with 3.6 percent of mothers experiencing this only during pregnancy and 4.6 percent only when children were preschoolers.

Children whose mothers were depressed only during their preschool years had the greatest level of behavioral and emotional problems, while kids whose mothers were only depressed during pregnancy didn't have any difficulties in these areas.

Women with chronic depression, whether moderate or more severe, had kids with some emotional or behavioral issues, the study found.

The results add to a growing body of research linking maternal depression to developmental problems in their children, said Erika Forbes, a child psychology researcher at the University of Pittsburgh. Generally, though, children are more at risk when families have other problems such as financial hardship or marital stress, Forbes, who wasn't involved in the current study, said by email.

The heightened risk experienced by preschoolers in the study suggests that the timing of maternal depression also plays a role in child development, Forbes said.

"During preschool, children's increasing independence but less-than-optimal self-control can make it especially challenging for mothers (or any caregivers) to set limits, grant autonomy and resolve conflicts," she said. "If mothers are depressed, they might find themselves too exhausted or emotionally taxed to engage in the kind of vigorous parenting that preschoolers tend to need."

While many women may experience what's commonly called "baby blues" for a few weeks after giving birth as they adjust to life with a new infant, symptoms that don't go away or that keep women from caring for their babies or engaging in normal activities might be depression, said David Bridgett, director of the Emotion Regulation and Temperament Laboratory at Northern Illinois University in DeKalb.

Medication or therapy may help ease symptoms of depression, but mothers might also need help learning new ways of interacting with their children, Bridgett, who wasn't involved in the study, said by email.

"Depression can affect parent-child interactions, which in turn, may be one way that maternal depression affects children," he said. "Because we know that children of mothers who are depressed are at higher risk of behavioral and emotional problems, they may need treatment as well."