Antidepressants Used During Pregnancy May Significantly Increase Autism Risk

A new study suggests women who take SSRIs during pregnancy could increase risk for autism by nearly 90 percent. REUTERS/Shannon Stapleton

Women who take antidepressants should seek out the advice of a physician if they wish to become pregnant, because new research suggests taking one popular class of the drugs—selective serotonin reuptake inhibitors (SSRIs)—during pregnancy can significantly increase a child's risk for autism.

The study, published Monday in JAMA Pediatrics, finds women who took SSRIs during pregnancy increased their child's risk for autism by as much as 87 percent. In particular, the study finds these medications may be most harmful to a fetus during the second and third trimester of a pregnancy. The researchers didn't observe the same link between antidepressant use and heightened autism risk when the drugs were taken in the first trimester.

"Given projections that depression will be the second leading cause of death by 2020, [antidepressants] are likely to remain widely used, including during pregnancy," the researchers write in their study. "Therefore, a better understanding of the long-term neurodevelopmental effects of [antidepressants] on children when used during gestation is a public health priority."

For the study, researchers at the University of Montreal analyzed data from the Quebec Pregnancy/Children Cohort that includes data on all children born in the city between January 1, 1998 and December 31, 2009, adding up to 145,456 infants. A total of 1,054 (0.72 percent) were diagnosed with autism and the average age of diagnosis was 4.6 years old.

The authors identified 4,724 infants (3.2 percent of the total sample) who were exposed to antidepressants in utero; 4,200 were exposed during the first trimester and 2,532 were exposed during the second and/or third trimester. A total of 31 children (1.2 percent of 2,532) who were exposed to antidepressants during the second and third trimester were diagnosed with autism, while 40 children (1.0 percent of 4,200) exposed during the first trimester later received an autism diagnosis. The study didn't account for errors that may occur in prescription filling data, a limitation the authors point out.

Though the exact reason for the association between SSRIs and autism risk isn't known, the authors suggest the drugs could alter neurotransmitter levels in utero. SSRIs work by blocking the serotonin transporter, which could cause a buildup of serotonin in the space between cells. When a pregnant woman is on SSRIs, the drug compounds can be found in her amniotic fluid. A high level of serotonin impacts early cellular development in a number of ways. There is also evidence that people with autism have higher levels of serotonin in blood platelets, and will lack the ability to synthesize serotonin. In people with autism, certain serotonin receptors are also altered in the cerebral cortex.

In one 2004 study published in Science, researchers gave pregnant mice SSRIs, and they observed notable biochemical differences in the offspring. Heightened levels of anxiety was one particularly noteworthy finding.

Alycia Halladay, chief science officer at the Autism Science Foundation, says that while this new research is certainly cause for some concern, it is important for women who take SSRIs to have an informed conversation with both their obstetrician and psychiatrist since stopping these drugs can also be detrimental to a mother's health. For many women, these medications are a lifeline and discontinuing them—and doing so suddenly—poses a risk for a depression and anxiety to return.

"I think the current paradigm that if you're pregnant you have to get off your medication is a little unfair," she says. "People on antidepressants should think very carefully if they want to stop taking medication."

Halladay says if anything, these findings suggest that more research is urgently needed to understand the link between SSRIs and autism risk. "This is a really tricky one, because it's not like advice such as wash your food or stay away from heavily polluted areas or eat green vegetables," says Halladay. "This is very complicated. I hope no one comes out of this and says 'OK, we're going to change our practice on a global level.'"