MONDAY, Sept. 10, 2012 (HealthDay News) -- Children of mothers who suffer from persistent postpartum depression are more likely to be very short at ages 4 and 5, new research finds.
Researchers examined data on 10,700 children from the nationally representative U.S. Early Childhood Longitudinal Study Birth Cohort. The children were born in 2001 and followed through 2007.
Children of mothers who were depressed during the first nine months of the child's life were 40 percent more likely to be at or below the 10th percentile for height at age 4, and 48 percent more likely to be at or below the 10th percentile for height at age 5 than children of mothers without depression.
Percentile compares how children measure up to other children the same age. Being in the 10th percentile means that the child is shorter than 90 percent of his or her peers.
"What we found is that mothers with higher levels of depressive symptoms in the first year postpartum were more likely to have children who were shorter in stature in preschool and kindergarten age," said lead study author Pamela Surkan, assistant professor at the Johns Hopkins Bloomberg School of Public Health, in Baltimore. "This study points to another reason why it's really important for mothers to get help for depression during the postpartum period."
The study is published online Sept. 10 and in the October print issue of the journal Pediatrics.
Experts aren't sure why maternal depression is associated with shorter children, but feeding practices and nutrition likely play a role, said Dr. Michelle Terry, an attending physician at Seattle Children's Hospital and clinical associate professor of pediatrics at the University of Washington School of Medicine.
One symptom of depression can be loss of appetite. "If I'm not hungry, I might not be that interested in what anybody else is eating, including the baby," Terry said.
Depressed mothers also may have insomnia, which could throw off a baby's sleep and feeding schedule. Feeding a baby is also a social interaction, Terry added. "If the mother has mood swings or is ambivalent, the baby may not look forward to eating as a social interaction time," she said.
"What is comes down to is a kind of neglect," she added.
According to the study, maternal depression also can cause children to feel stressed. Chronically high levels of the stress hormone cortisol are associated with lower levels of the growth hormone in children.
Although researchers found an association between maternal depressive symptoms and shorter children, they did not prove that the mother's depression caused the children to be shorter.
Nor did researchers find an association between depression in mothers and skinnier kids -- that is, the children of depressed mothers weren't more likely to be underweight for their height or age.
And, researchers noted, being in the 10th percentile for height isn't necessarily a bad thing. If children have short parents, the kids are likely to be short too.
"If you are small because your parents are small, and genetically you were supposed to be in the 10th percentile, that's fine," Surkan said. "But if the reason you're in the 10th percentile is because you lacked nutrition or because you had a number of illnesses over the course of your early childhood that weren't treated properly, that is a problem."
Stunted growth (usually defined as the 5th percentile or less for height) is associated with higher risk of some diseases and death in childhood and even in the long term, Surkan said.
Previous research also has shown that maternal depression can lead to poorer development, including decreased growth, in the first two years of life, according to background information in the study.
Washington's Department of Early Learning has more on postpartum depression.