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In utero antidepressant exposure does not increase autism risk

Recent findings indicated that children exposed to serotonergic antidepressants in utero did not have increased risk for autism compared with unexposed children.

“Both environmental and genetic factors are thought to cause autism spectrum disorder. The serotonin hypothesis of autism posits that fetal exposure to elevated serotonin levels could result in autism spectrum disorder,” Hilary K. Brown, PhD, of Women’s College Hospital, Toronto, and colleagues wrote. “Animal studies suggest that in utero exposure to serotonergic antidepressants such as [selective serotonin reuptake inhibitors (SSRIs)] could lead to dysfunctional serotonin signaling and loss of serotonin terminals in exposed fetuses, resulting in the autism phenotype.”

To assess the association between serotonergic antidepressant exposure during pregnancy and autism spectrum disorder (ASD), researchers analyzed health administrative data for children born to mothers receiving public prescription drug coverage during pregnancy in Ontario from 2000 to 2010. Children were followed until April 2014. Serotonergic antidepressant exposure was defined as two or more consecutive maternal prescriptions for SSRIs or serotonin-norepinephrine reuptake inhibitors between conception and delivery. ASD was identified after age 2 years.

Overall, there were 35,906 singleton births at a mean gestational age of 38.7 weeks.

Of the 2,837 pregnancies exposed to antidepressants, 2% of children were diagnosed with ASD.

Incidence of ASD was 4.51 per 1,000 person-years among children exposed to antidepressants, compared with 2.03 per 1,000 person-years among unexposed children (HR = 2.16; 95% CI, 1.64-2.86; adjusted HR = 1.59; 95% CI, 1.17-2.17).

This association was insignificant after inverse probability of treatment weighting based on high-dimensional propensity scores.

Further, the association was not significant when comparing exposed children with unexposed siblings, with ASD incidence of 3.4 vs. 2.05 per 1,000 person-years, respectively.

Another study in this issue of JAMA explored associations between first trimester antidepressant exposure and neurodevelopmental outcomes, including ASD and ADHD.

Ayesha C. Sujan , MA, of Indiana University, Bloomington, and colleagues found that first trimester maternal antidepressant use was associated with a slight increased risk for preterm birth, but not with adverse neurodevelopmental outcomes.

“Together these two new studies add to a growing literature suggesting that the association between prenatal antidepressant medication exposure and autism spectrum disorder may not be causal. These data should reassure both parents and clinicians,” Tim F. Oberlander, MD, FRCPC, of University of British Columbia, Vancouver, and Lonnie Zwaigenbaum, MSc, MD, FRCPC, of University of Alberta, Edmonton, wrote in an accompanying editorial. – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.