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Research Points to Shared Environmental Factors for Autism and ASD: Page 3 of 4

Research Points to Shared Environmental Factors for Autism and ASD: Page 3 of 4

Replication

Some efforts are under way that will facilitate replication and extension of the antidepressant study, according to Croen.

One is the Study to Explore Early Development (SEED), a national, multisite, case-control, large, epidemiological study funded by the CDC. Croen is one of the site investigators.

“We have very comprehensive information on all sorts of things in that study, including medication use and illnesses during pregnancy and a very large sample size (more than 3500 children and their parents). So that’s one opportunity to try and replicate these findings,” she said.

Recruitment for phase 1 of the SEED study is complete, Croen said, and investigators are beginning to analyze the data. The CDC has funded a second phase of the study that will involve recruitment and data collection for a new cohort of children.

Croen also is a principal investigator on the Early Autism Risk Longitudinal Investigation (EARLI)—a prospective cohort study in which women with 1 or more children already affected by ASD are being followed.

“We are following subsequent pregnancies of those women through the pregnancy and early years of their new baby’s life,” Croen said, adding that enrollment is about 30% complete. “In that study, we have very comprehensive data collection during pregnancies, including illnesses and medication use, and then we will have the outcome of the babies.”

In both studies, Croen said investigators are obtaining biological samples, so they “have the ability to look at genetic factors in combination with nongenetic factors, such as medication use or illness.”

When the data are ready, Croen said, both studies will have an op­portunity to examine the question of SSRI use and autism. She is also planning a study within the Kaiser system to examine the issue in more depth with an enhanced sample size.

Another medication class Croen and colleagues studied recently was β2-adrenergic receptor agonists (B2AR agonists) and the risk of ASD.4

Some reports indicate “that these types of medications with these properties have an effect on neurodevelopment and yield the kinds of abnormalities in brain and behavior that are represented by autism,” Croen said.

In a recently reported study, Croen and colleagues found that exposure to B2AR agonists other than terbutaline (Brethine, Bricanyl) was not associated with an increased risk of ASDs. But terbutaline exposure for more than 2 days (usually between 10 and 12 days) during the third trimester was associated with more than a 4-fold increased risk of ASDs, independent of indication.

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