Both untreated maternal depression and a common kind of antidepressant medication seem to affect a crucial period in a baby’s language development, a new study asserts.

University of British Columbia pediatrician Tim Oberlander and colleagues from UBC and Harvard University examined 85 infants – 32 whose mothers were being treated with serotonin reuptake inhibitors (a class that includes drugs like Prozac, Paxil and Celexa), 21 infants whose mothers had untreated prenatal depression, and 32 babies whose mothers were not diagnosed with depression nor taking SRIs.

“We already know that maternal depression both during pregnancy and postnatally influences a variety of domains of infant development — attachment to mother, cognition, behavior, and temperament, for example,” Oberlander explained in a phone interview.

He and his colleagues outlined their findings in a paper published Monday in the Proceedings of the National Academy of Sciences.

The team examined the infants at six and 10 months of age to see how they reacted to sounds and videos of both their parents’ native language and a non-native language. They also looked at the heart rate responses to language in 34 unborn fetuses, 14 of which were being carried by mothers taking SRI antidepressants.

SRI-exposed fetuses and babies had an accelerated ability to attune to the sounds of their native language, showing a more mature pattern of what’s called “perceptual narrowing.” Meanwhile, infants born to mothers with untreated depression showed the opposite effect.

But, Oberlander is quick to caution, it is still unclear exactly what these effects mean in terms of larger consequences on language acquisition.

The key point, he says, is that it is important to recognize and manage a mother’s mood during pregnancy.

“There’s no free lunch here -- both depression and its treatment affect infant and child development," Oberlander said. But of course "it’s important that the mother’s mental health gets sufficient attention."

SOURCE: Weikum et al. “Prenatal exposure to antidepressants and depressed maternal mood alter trajectory of infant speech perception.” PNAS published online 8 October 2012.