Autism Risk in Siblings  Interview with: Therese Koops Grønborg

PhD student/ph.d.-studerende, MSc
Section of Biostatistics/Sektion for Biostatistisk
Department of Public Health/Institut for Folkesundhed
Aarhus University
Bartholins Allé 2, DK-8000 Aarhus C, Denmark What are the main findings of the study?

Answer: There are three important findings in our study.

We estimated a population-based Autism Spectrum Disorder (ASD) sibling recurrence risk relative to the background population and found an almost seven-fold increase. While this indeed is an increased risk, it is also lower than what other recent studies have suggested.

We also compared the relative recurrence risk for full and maternal/paternal half siblings and found a lower relative recurrence risk in half siblings than in full siblings, which supports the genetic pathway to ASD. The recurrence risk for maternal half siblings is still higher than for the background population suggesting that factors unique to the mother, such as the intrauterine environment and perinatal history, may contribute to ASD.

Last, but not least, we estimated the time trends in the relative recurrence risk. While the ASD prevalence has been increasing for several years, we found no time trends in the relative recurrence risk, suggesting that the factors contributing to the risk for ASDs recurrence in siblings (perhaps a combination of genes and environment) have not changed over time. Were any of the findings unexpected?

Answer: I think we were a bit surprised the relative recurrence risk came out so low. We did not know what to expect about the trends over time, but it is very interesting that while the ASD prevalence has increased during the last two decades, the relative recurrence risk has more or less remained constant in the same time period. What should clinicians and patients take away from your report?

Answer: If you have a child with ASD the risk of having another child with the same condition is about 7%, which is lower than what other recent studies have suggested. Whether that is considered a high or low risk is up to each affected family to decide. This is an average based on many families and individual counseling to each family is necessary. As we also acknowledge in our article, there is a possibility that this is an underestimate for families with the more severe ASD cases. What recommendations do you have for future research as a result of this study?

Answer: It would be interesting to investigate families with at least two affected children and consider the subsequent children. This would require a large data pool since there are not that many of these families. Also, when the individuals from our study are old enough to have had children of their own and some of these children also have been diagnosed with ASD, it would be of great interest to study the parent-child recurrence risk. But, we’ll have to wait some years for that.

If possible, it would also be interesting to expand the full and half siblings analysis with information about which parent the children are living with.


Therese K. Grønborg, Diana E. Schendel, Erik T. Parner. Recurrence of Autism Spectrum Disorders in Full- and Half-Siblings and Trends Over TimeA Population-Based Cohort Study. JAMA Pediatrics, 2013 DOI: 10.1001/jamapediatrics.2013.2259


Last Updated on September 19, 2013 by Marie Benz MD FAAD