When an expectant mother uses antidepressants during the latter stages of pregnancy, the chances of her child developing autism goes up by 87 percent, according to a report released today in JAMA Pediatrics.

Dr. Anick Bérard, a professor at the University of Montreal looked at data from nearly 150,000 pregnancies. She found that women who took antidepressants – namely serotonin reuptake inhibitors, or SSRIs – during the second or third trimester of pregnancy almost doubled the risk that their child would be diagnosed with autism by age 7. The same risk was not found in women who used antidepressants during the first trimester.

Autism among children has increased from 4 in 10,000 in 1966 to 100 in 10,000 today. That increase has been attributed to better detection methods and broader diagnostic criteria. Some experts suspect that environmental factors also contribute to the increase in cases.

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What the Study Revealed

During the study, Bérard examined data of 145,456 children from conception up to age 10. In the study, 1,054 children were diagnosed with autism at an average age of 4 and a half.

The subjects were anyone who had had one or more antidepressant prescriptions filled during the second or third trimester of the pregnancy, which is a critical time for infant brain development. The team took into account a variety of factors, including genetic predisposition to autism, maternal age, depression, and certain socioeconomic factors.

Maternal depression was associated with a 20 percent increased risk of a child having autism in the study, Bérard said.

“It is biologically plausible that anti-depressants are causing autism if used at the time of brain development in the womb, as serotonin is involved in numerous pre- and postnatal developmental processes,” Bérard said in a statement.

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No Definitive Cause and Effect

“This study does not provide a definitive statement about whether antidepressants cause autism,” Dr. Bryan H. King, the program director at the Seattle Children's Autism Center at Seattle Children’s Hospital, said. He also wrote an editorial published with the study.

King said the report indicates that prenatal development is likely an important area to focus on when understanding factors that may contribute to autism, but it does not establish antidepressant use during pregnancy as a cause for autism.

He noted that there are about half a dozen studies that have used similar methods to try to find a link between autism and antidepressant use during pregnancy.

“Not all have found a signal, and those that have are reporting something on the order of a 1 percent increase in autism births in exposed children,” King said. “This study is reporting about 0.5 percent.”

That means that for every 200 mothers who continue their antidepressants during pregnancy, there may be one more child with autism than would be expected, according to King. 

He noted that there wasn’t a control group, so researchers couldn’t discern if other negative outcomes were prevented by antidepressant treatment in the pregnancies. Additionally, it’s unknown if the risk signal that this study indicates is due to antidepressant exposure or a genetic risk from depression.

However, it is important to remember that findings from the studies on this topic are mixed, King added.

“Taken together and looking only at autism risk, the consistent finding is that if there is a risk signal that can be attributed to antidepressants during pregnancy, that it is quite small,” he said.

Bérard noted the study was observational because randomized controlled trials are not ethically possible during pregnancy.

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Depression a Serious Health Problem

The World Health Organization indicates that depression will be the second leading cause of death by 2020. That has lead researchers to conclude that antidepressants will likely to remain widely prescribed, including during pregnancy.

As many as 6 to 10 percent of pregnant women take antidepressants. About 80 percent of pregnant women who are depressed experience anywhere from mild to moderate symptoms.

Bérard said her team doesn’t advocate leaving depression untreated, but they advise that women explore other treatments – such as exercise and psychotherapy – in most cases.

“The common belief is that depression can only be treated with antidepressants, which is false,” she told Healthline.

“Our study is not to scare women,” Bérard said. “Women can make an informed decision, but they need to have evidence-based data. A discussion with their physician is warranted in order to fully consider all treatment options.”

Dr. Nicole Smith, who works for the Division of Maternal Fetal Medicine at Brigham and Women’s Hospital in Boston, said some women with severe depression should be on antidepressants during pregnancy.

“Untreated depression in pregnancy can be harmful for mothers and their babies,” she told Healthline. “While there may be small risks associated with antidepressant use in pregnancy, for some women these risks are outweighed by the negative consequence of not taking medication.”

She added that studies have been inconsistent at pinpointing a link between antidepressants and autism.