A common class of antidepressants, when taken during pregnancy, can affect aspects of language ability in the baby's earliest stages of development, a small new study suggests.
The study found that treating depressed pregnant women with serotonin re-uptake inhibitors (SSRIs) may speed up the baby's ability to focus on the sights and sounds of his or her native language.
"This study shows how maternal depression and its treatment can change the timing of language development in babies," said Janet Werker, professor of psychology at the University of British Columbia, in Vancouver, Canada, and senior author of the study.
Werker stressed that the study does not show that the "sped-up" development associated with pregnant mothers who took these antidepressants was necessarily beneficial to the infant's language learning process.
"In our culture we tend to think speeding things up is a good thing, but it's not necessarily so with infant language development," Werker said.
The study also found that depression during pregnancy not treated with medication may prolong an early stage of language development. The study appears Oct. 8 in the journal Proceedings of the National Academy of Sciences.
Serotonin is a hormone that regulates mood, appetite and sleep, and is thought to contribute to feelings of well-being and happiness. SSRIs raise the amount of serotonin available outside of cells, which increases the ability of nerve cells to transmit serotonin. SSRIs also are used to treat anxiety and eating disorders.
SSRIs include commonly prescribed antidepressants such as Prozac (Fluoxetine), Lexapro (escitalopram), Paxil (paroxetine) and Zoloft (sertraline).
The new research is the latest in a growing body of evidence showing that both depression in pregnancy and drugs taken to fight the disorder can affect fetal development, which can create a treatment dilemma for women and their doctors.
For example, another study, published in March in the journal Archives of General Psychiatry, showed that pregnant women taking SSRIs may be more likely to deliver infants with smaller heads.
Werker said the new research does not explain why only some infants are affected by either a mother's depression or by treatment with SSRIs.
The study followed three groups of pregnant women: those being treated for depression with SSRIs, those who were depressed but not taking the medications and others who were not depressed. Depressed women not on SSRIs were getting some form of non-drug therapy, Werker said.
The research involved two experiments. The first looked at 85 infants in the first year of life -- 32 from mothers who were not depressed during pregnancy, 21 whose mothers were depressed but not treated with SSRIs and 32 whose mothers were depressed and treated with SSRIs.
Measuring changes in heart rate and eye movement in response to sounds and video images of speakers of both native and non-native languages, the researchers assessed the infants' language development at 6 months and 10 months of age.
In the second experiment, 14 fetuses whose mothers were taking SSRIs and 20 fetuses whose mothers were not taking the medications were tested. The researchers measured how their heart rate changed in response to different sounds.
They found some significant differences in how infants responded to language differences and how fetuses responded to sound, when looking at whether their mothers were treated with SSRIs.
An expert who reviewed the new research said it had several limitations, however.
Among these was that the study did not identify whether the impact on language development might be long term, a common limitation of SSRI-related studies.
"If these effects are transient, does it really make any difference?" asked Victoria Richards, a pharmacologist and assistant professor at the Frank H. Netter School of Medicine at Quinnipiac University, in Hamden, Conn.
The study would have been more valuable if it had described the specific severity of depression in the study participants, revealed who had diagnosed the depression and on what criteria the diagnosis was based, and noted whether the SSRI was appropriately prescribed, Richards said.
It would have been interesting to assess whether women receiving behavioral therapy, rather than medication, for their depression had babies with delayed or more advanced language development, she said.
Richards explained that, for women, the decision about whether to take SSRIs during pregnancy can be complicated.
"The human body is so complex," she said. "When you're pregnant, it inherently changes the way drugs are handled by the body, and with a growing fetus, you have to weigh the risks and the benefits."
Women who are taking SSRIs and are pregnant or considering pregnancy should not stop taking the medications without talking with their prescriber, Richards said. She warned that there can be serious implications to suddenly going off this class of drugs.
Although the study found an association between antidepressant use in pregnancy and babies' language development, it did not prove a cause-and-effect relationship.
