Moms who live with depression are often issued warnings about how mood disorders may affect their babies. One study found that being depressed during pregnancy doubles risk of preterm birth, while another recent report tied postpartum depression to shorter stature in kids.
A small new study adds to the research on maternal depression and its potential effects, finding that untreated depression makes it take longer for babies to "attune" to the sounds and sights of their native language. This process is a key part of learning to speak, which babies do by listening to people around them and watching facial movements. On the other hand, treating maternal depression with serotonin reuptake inhibitors (SRIs), a type of antidepressants, seemed to speed that process up.
"By better characterizing how developing systems in the brain function, we are better positioned in the future to ask more precise questions about the effects of maternal depression, and to learn more -- mechanistically -- about how different forms of treatment affect the developing brain," Janet Werker, a psychologist at the University of British Columbia in Canada and an author of the study, told HuffPost.
To look at the question of how maternal depression and treatment of it with antidepressants affects early language development skills, Werker and her colleagues looked at 85 babies: 21 whose mothers were not treated with antidepressants and 32 whose were. (The remaining babies were controls.) They examined them in utero -- at 36 weeks -- to gauge their ability to discriminate between consonant and vowel changes by measuring changes in their heart rate. When the babies were 6 and 10 months old, they played them recordings of different pronunciations of syllables and showed them silent videos of people speaking English or French, monitoring how long the babies looked in order to gauge whether they perceived changes.
"Exposure to SRI medication in utero accelerates the age by which infants become attuned to the properties of the native language," said Werker. On the other hand, children whose mothers were depressed but did not receive treatment had delays when they began this key learning process.
The reasons why this happens are not yet clear, but Werker offered two possible explanations: Babies whose moms are treated with SRIs may be exposed to "downstream influences" from the antidepressants that affect neurotransmitter systems in the brain. Conversely, depression that goes untreated may have neuro-chemical consequences that cause delays in these critical periods of learning. After birth, moms' depression may cause them to speak in less engaged and engaging ways, which could play a role.
"Babies might have less exposure to the kind of speech their developing systems are waiting for," Werker said. "Hence, the developmental trajectory could be slowed down."
Estimates cited in the study, which was published in the journal PNAS on Monday, say that between 15 and 20 percent of pregnant women experience mood disorders, such as depression, and up to 13 percent are treated with antidepressants. Mental health experts generally advise women to consult with their doctors in order to weigh the risks of taking antidepressants during pregnancy with the potential benefits.
But Werker stressed that the new findings are preliminary and should not yet enter into that conversation, nor should they change best practices for treatment of maternal depression.
"They do, however, show that with careful research into the mechanisms by which systems develop, we can be in a better position to advise about such practices in the future," she said.