Autism Risk Increases With Antidepressant Use During Pregnancy
A large-scale study has found a link between antidepressant (AD) use during the second and/or third trimester of pregnancy and an increased risk of autism spectrum disorder (ASD) in children by 87%.
Researchers, lead by Anick Berard, PhD, of the University of Montreal, analyzed birth data in Quebec from January 1998 to December 2009. In this time there were 145,456 babies born. The study counted all ASD diagnoses from the time of birth until date of diagnoses, death, or the conclusion of the study (December 31, 2009). The average age of the children at the final follow up was 6.24.
Those exposed to ADs in utero numbered 4724 (3.2%), of these 4200 (89.9%) were exposed during the first trimester, and 2532 (53.6%) during the second and/or third trimester. In total there were 1054 (0.72%) diagnoses of ASD. Forty-six of these diagnoses (0.97%) were exposed to ADs in utero, while 1008 (0.71%) were not.
Saliently, researchers found that exposure to ADs in the second and/or third trimester led to greater ASD risk, with thirty-one (1.2%) of these infants diagnosed. This represents an 87% increased risk of ASD when compared with 0.71% of ASD diagnosed infants who were not exposed to ADs. The number of average ASD diagnoses is consistent with study cases published in the last 15 years, which found approximately 0.7% diagnoses with comprisable data selections.
Multiple AD classes were included in the study, however the increased risk of ASD was only found with selective serotonin reuptake inhibitors (SSRIs) use, and if the mother used more than one class of AD.
Antidepressant usage in the US during pregnancy has been on the rise; from 5.7% in 1999 to 13.3% in 2003. The study does cite how discontinuation of ADs during pregnancy is associated with relapses, but also that 20% of women who continue AD use during pregnancy remain depressed.
Several mechanisms may account for the increased risk of ASD associated with maternal use of SSRI during pregnancy. SSRI's cross the placenta and are found in amniotic fluid. The authors point to how individuals with ASD have unusually high levels of serotonin in blood platelets. The capacity of the brain to synthesize serotonin develops atypically in children with ASD.
The authors identified their use of prescription filling data as a limiting factor in the study, because prescriptions do not necessarily reflect actual usage. However, prescriptions are still the most accurate source for estimating medication intake when studying such populations. The large scale of this study make the findings stark, however the authors call for more research on assess the risk of ASD associated with antidepressant types and dosages during pregnancy.