Both having depression and taking antidepressants during pregnancy may affect an infant's language development, new research suggests.

Study results reveal that a crucial language development period, during which infants learn to tune in to the sounds of their native language, is sped up when women take antidepressants, and prolonged when a woman has depression.

However, the researchers are not sure whether such speeding up or slowing down is beneficial or harmful in the long run, and it may not have any effect on a baby's ultimate ability to acquire language, said Janet Werker, a professor of psychology at the University of British Columbia.

Werker discussed her findings here at the American Association for the Advancement of Science's annual meeting.

Babies are born with the ability to learn any language, and can distinguish between sounds of a variety of different tongues. However, by the age of 6 to 10 months, they begin to take more notice of the sounds of their native language, and are less able to discriminate between sounds of other languages.

In the new study, Werker and colleagues tested the ability of babies born to mothers with and without depression to discriminate between consonant sounds in a non-native language.

Babies of mothers without depression showed the normal pattern of development — they could discriminate between the consonant sounds at 6 months old, but by 10 months old, they had lost this ability.

In contrast, babies of mothers with depression could still discriminate between the sounds by age 10 months.

Interestingly, babies of mothers with depression who took serotonin reuptake inhibitors, or SRIs (a type of antidepressant) could not discriminate between the consonant  sounds at either 6 or 10 months old.

The researchers wondered if this period of development had been shifted to even earlier in life. To find out, they studied the heart rates of fetuses during the 36th week of pregnancy (babies are considered full term starting at 37 weeks). A decrease in heart rate in response to a stimulus is indicative of discrimination, Werker said.

Sure enough, babies of mothers who took SRIs could discriminate between the consonant sounds in utero, just before they were born. Future studies are needed to learn how this shift ultimately affects speech and language development, Werker said.

Because of the effects of poor mental health on both mothers and their babies, woman should be screened for depressionbefore and during pregnancy so it can be effectively managed, said Dr. Tim Oberlander, a professor of developmental pediatrics at University of British Columbia. Regardless of whether a woman takes SRIs, "non-treatment is never an option," Oberlander said.

The decision for depressed women take medication during pregnancy is a personal one to be made between a woman and her doctor, Oberlander said. "To say one size fits all is not fair or reasonable," he said.

Pass it on: Both depression and antidepressants during pregnancy can shift an infants' ability to tune to their native language, but it's not clear whether this change is good, bad or doesn't matter.