In short, what is the study about?
The environmental contributions to autism spectrum disorder (ASD) and their informative content for diagnosing the condition are still largely unknown.
The objective of this study was to explore associations between peri- and early postnatal factors, ASD, and autistic traits. Specifically, we sought to identify early medical events likely to be caused by environmental factors, not shared among family members, which are associated with ASD. Next, we wanted to test the hypothesis of their cumulative effect on ASD risk status.
For this purpose, we scrutinized the early medical histories from in-depth reviews of medical records of a rare and informative sample of 13 monozygotic (identical) twin pairs discordant for clinical ASD diagnoses, and 13 monozygotic typically developed control pairs. The factors identified in this smaller sample (N=52) were then cross-validated in an independent larger cohort of monozygotic and dizygotic twins discordant for autistic traits (N=200). The identified single factors were operationalized into a cumulative multifactorial model.
What would be the most important take-home messages from the study?
The findings of our study show a cumulative association between the total load of early medical events and ASD, clinical diagnoses as well as autistic traits. In other words, the more of the identified pre- and early postnatal medical events the child is exposed to, the higher risk that the child later will develop ASD or autistic traits. In particular, infant dysregulation (feeding, sleeping abnormalities, excessive crying, and worriedness), are associated with an increased risk of clinical ASD and as well as autistic traits. In our study, we show that the results are specific for ASD and hold true even when adjusting for possible confounding factors such as genetic variation, environmental factors shared within twin pairs (e.g. sex, age, socioeconomic status), intelligence quotient (IQ) and attention deficit hyperactivity disorder (ADHD) comorbidity.
How are these findings important in practice?
Our study shows the novel finding of a cumulative environmental effect on ASD risk when adjusting for the genetic factors as well as many other potential confounders. In addition, we were able to replicate previous findings of early dysregulation as a precursor of behavioral problems and autistic traits.
Taken together the results provide information about early medical events and adverse behavioral manifestations that may index children at risk for ASD, owing to environmental influences. Our findings suggest that the information of the total load of early medical events and infant dysregulation might facilitate early detection of ASD, as it might either further support or discourage an existing diagnostic suspicion.
Bölte S, Willfors C, Berggren S, Norberg J, Poltrago L, Mevel K et al. The roots of autism and ADHD twin study in Sweden (RATSS). Twin Res Hum Genet 2014; 17: 164–176.
Arora, M., Reichenberg, A., Willfors, C., Austin, C., Gennings, C., Berggren, S., Lichtenstein, P., Anckarsäter, H., Tammimies, K., & Bölte, S. Fetal and Postnatal Metal Dysregulation in Autism. Nature Communication. Advance online publication. doi:10.1038/ncomms15493. Retrieved from http://www.nature.com/tp/journal/v7/n1/abs/tp2016269a.html