Women who are depressed while pregnant may be more likely than other expecting moms to have kids who are physically aggressive as teens, a new study finds.
In addition, women in the study who were themselves aggressive as teens were more likely to get depressed during pregnancy.
The findings don't mean a woman who suffers from the blues while pregnant is doomed to misbehaving children, who bully others and get into fights. But it does highlight an issue that the researchers say needs attention.
"Much attention has been given to the effects of postnatal depression on young infants," said study researcher Dale F. Hay, professor of psychology at Cardiff University in Wales. "But depression during pregnancy may also affect the unborn child."
Hay and her colleagues looked at data collected from 120 British teens and their parents from inner-city areas. The youth were interviewed at 4, 11 and 16 years of age.
About one-third of expecting moms were considered depressed during pregnancy, which is higher than the current worldwide estimate of about 18 percent of pregnant women, Hay said. The researchers say socioeconomics could explain some of that discrepancy since the participants lived in relatively disadvantaged urban areas.
Teens born to mothers who were depressed during pregnancy were four times more likely than others to show violent behaviors by age 16. While 8.5 percent of teens born to chipper expecting moms showed the antisocial behaviors, about 29 percent of those born to depressed moms showed the same.
This same link wasn't found between depressed expecting moms and teens' non-violent but deviant behaviors, such as shoplifting.
Statistical analyses showed women who were aggressive and disruptive as adolescents were more likely to get depressed while pregnant. So it's a combination of factors.
"What you have is a set of women who themselves may have had troubled adolescence in that they had behavioral and conduct problems," Hay said. "They are the ones who have a higher risk of becoming depressed during pregnancy, and those two factors together combine to predict the children who are at most risk for being violent themselves."
The results held even after accounting for mothers' anxiety and depression prior to getting pregnant, smoking and drinking alcohol during pregnancy, and the kids' exposure to depressed moms.
Hay and her colleagues aren't sure what's behind the link.
"There's a lot of work that suggests that there could be mechanisms whereby the mother's depression is associated with biological changes that affect the developing nervous system," Hay told LiveScience, adding, "I don't have evidence for it in this sample."
Genetics also likely plays a role since moms who were delinquents as adolescents had teens who showed similar misconduct. However, this study didn't look at genetics.
"Although it's not yet clear exactly how depression in pregnancy might set infants on a pathway toward increased antisocial behavior, our findings suggest that women with a history of conduct problems who become depressed in pregnancy may be in special need of support," Hay said.
Hay and her colleagues detail their findings in the January/February issue of the journal Child Development.