Link between prenatal antidepressant exposure, autism risk called into question

The authors note that, while genetic factors are known to play a substantial role in autism, exactly how that risk may be exacerbated by environmental factors is not well understood. While animal studies and investigations based on health records have suggested an increased risk associated with prenatal antidepressant exposure, others found no such association. Credit: © milosducati / Fotolia

Previous studies that have suggested an increased risk of autism among children of women who took antidepressants during pregnancy may actually reflect the known increased risk associated with severe maternal depression. In a study receiving advance online publication in Molecular Psychiatry, investigators from Massachusetts General Hospital (MGH) report that -- while a diagnosis of autism spectrum disorder was more common in the children of mothers prescribed antidepressants during pregnancy than in those with no prenatal exposure -- when the severity of the mother's depression was accounted for, that increased risk was no longer statistically significant. An increased risk for attention-deficit hyperactivity disorder (ADHD), however, persisted even after controlling for factors relating to a mother's mental health.

"We know that untreated depression can pose serious health risks to both a mother and child, so it's important that women being treated with antidepressants who become pregnant, or who are thinking about becoming pregnant, know that these medications will not increase their child's risk of autism," says Roy Perlis, MD, MSc, MGH Department of Psychiatry, senior author of the report.

The authors note that, while genetic factors are known to play a substantial role in autism, exactly how that risk may be exacerbated by environmental factors is not well understood. 

While animal studies and investigations based on health records have suggested an increased risk associated with prenatal antidepressant exposure, others found no such association. And since discontinuing antidepressant treatment significantly increases the risk of relapse -- including an increased risk of postpartum depression -- the current study was designed to clarify whether or not any increased autism risk could actually be attributed to the medication.

To investigate this possibility, the research team analyzed electronic health record data for children born at MGH, Brigham and Women's Hospital, or Newton Wellesley Hospital -- hospitals belonging to Partners HealthCare System -- for whom a diagnostic code for pervasive developmental disorder, a category that includes autism, was entered at least once between 1997 and 2010. They matched data for almost 1,400 such children with that of more than 4,000 controls with no autism diagnoses, born the same years and matched for a variety of demographic factors.

The children's information was paired with that of their mothers, noting any factors related to the diagnosis and treatment of major depression or other mental illness, including prescriptions for antidepressants and other psychotropic drugs. A similar analysis was done for almost 2,250 children with an ADHD diagnosis, compared with more than 5,600 matched controls with no ADHD diagnoses.

While prenatal exposure to antidepressants did increase the risk for either condition, in the autism-focused comparison, adjusting for factors indicating more severe maternal depression reduced the strength of that association to an insignificant level. Taking antidepressants with stronger action in the serotonin pathway, which has been suspected of contributing to a possible autism risk, did not increase the incidence of the disorder. In addition, the children of mothers who took a serotonin-targeting non-antidepressant drug for severe morning sickness had no increased autism incidence. Prescriptions for antipsychotic drugs sometimes used to treat severe, treatment-resistant depression, as well as psychotic disorders, did appear to increase the risk for autism. For ADHD, however, the increased risk associated with prenatal antidepressant exposure remained significant, although reduced, even after adjustment for the severity of maternal depression.

"There are a range of options -- medication and non-medication -- for treating depression and anxiety in pregnancy," says Perlis, an associate professor of Psychiatry at Harvard Medical School. "But if antidepressants are needed, I hope parents can feel reassured about their safety."

Source: Massachusetts General Hospital

Fine particulate air pollution linked with increased autism risk

The greater the exposure a pregnant woman has to fine particulate matter, the greater the risk of their baby having autism, researchers found. Credit: © Oleg Shelomentsev / Fotolia

Women exposed to high levels of fine particulate matter specifically during pregnancy--particularly during the third trimester--may face up to twice the risk of having a child with autism than mothers living in areas with low particulate matter, according to a new study from Harvard School of Public Health (HSPH). The greater the exposure, the greater the risk, researchers found. It was the first U.S.-wide study exploring the link between airborne particulate matter and autism.

"Our data add additional important support to the hypothesis that maternal exposure to air pollution contributes to the risk of autism spectrum disorders," said Marc Weisskopf, associate professor of environmental and occupational epidemiology and senior author of the study. "The specificity of our findings for the pregnancy period, and third trimester in particular, rules out many other possible explanations for these findings."

The study appears online December 18, 2014 in Environmental Health Perspectives.

Prior studies have suggested that, in addition to genetics, exposure to airborne environmental contaminants, particularly during pregnancy and early life, may affect risk of autism. This study focused specifically on the pregnancy period.

The study population included offspring of participants living in all 50 states in Nurses' Health Study II, a cohort of more than 116,000 female U.S. nurses begun in 1989. The researchers collected data on where participants lived during their pregnancies as well as data from the U.S. Environmental Protection Agency and other sources on levels of fine particulate matter air pollution (PM2.5)--particles 2.5 microns in diameter or smaller--in locations across the U.S. The researchers identified 245 children who were diagnosed with autism spectrum disorder (ASD) and a control group of 1,522 children without ASD during the time period studied.

The researchers explored the association between autism and exposure to PM2.5 before, during, and after pregnancy. They also calculated exposure to PM2.5 during each pregnancy trimester.

Exposure to PM2.5 was significantly associated with autism during pregnancy, but not before or after, the study found. And during the pregnancy, the third trimester specifically was significantly associated with an increased risk. Little association was found between air pollution from larger-sized particles (PM10-2.5) and autism.

"The evidence base for a role for maternal exposure to air pollution increasing the risk of autism spectrum disorders is becoming quite strong," said Weisskopf. "This not only gives us important insight as we continue to pursue the origins of autism spectrum disorders, but as a modifiable exposure, opens the door to thinking about possible preventative measures."

Source: Harvard School of Public Health