Everybody knows that parents' genes help determine children's heights, but new research suggests another, less obvious factor may play a role in how tall kids get. A study published in the journal Pediatrics says a mother's emotional state in the first year of her baby's life might affect his or her growth. Do depressed mothers raise shorter children? Here, a brief guide:
What did the study find?
The researchers examined data on 6,500 kids from 2001 to 2007, looking at the height of the children at 9 months, 4 years, and again at 5 or 6 years of age. Then they cross-referenced this data with information about mothers' emotional states. The result? The 4-year-olds whose moms had experienced mild or moderate post-partum depression were 40 percent more likely to be short — in the 10th percentile of height — than those whose moms weren't depressed when their kids were infants. By age 5, the children of depressed moms were 48 percent more likely than their peers to be short.
But does depression cause shortness?
The researchers couldn't say for sure. "The study doesn't prove that mom's depression causes a child's short stature," says Alexandra Sifferlin at TIME, "only that the two are associated." The authors didn't come up with evidence to explain why the mom's mental health and the child's height appear to be linked. But they did have several theories.
What might cause this link?
One possibility is that a mother's depression could increase the stress levels felt by her kids, and high levels of the stress hormone cortisol have been linked to low levels of growth hormones in kids. Another possibility: Depressed mothers are more likely to have poor feeding practices, such as spending less time than other mothers breastfeeding, which could affect height. Previous studies have already tied postpartum depression to other developmental issues, such as language and cognitive delays, and behavioral problems.
What's the best way to deal with this?
The Centers for Disease Control and Prevention recommend that a mother who experiences the symptoms of post-partum depression — trouble sleeping when her baby sleeps, feeling numb, worrying that she can't care for the child, feeling ashamed that she's not a good mom — consult a counselor. The authors of the study agree, saying that spotting and treating depression is important for mother and child alike. "There's already very good reasons that mothers who are depressed should seek treatment," says Pamela Surkan, lead author of the study. "This is one more additional piece of evidence confirming that this is important."