The current issue of the Journal of the American Academy of Pediatrics features a published study conducted to look at the recurrence risk for ASD’s. “The recurrence risk of autism spectrum disorders (ASD) is estimated to be between 3% and 10%, but previous research was limited by small sample sizes and biases related to ascertainment, reporting, and stoppage factors” (Pediatrics, Sept 2011).
The study method used at risk children for ASD from an international network, the Baby Siblings Research Consortium. The “infants with an older biological sibling with ASD were followed from early in life to 36 months, when they were classified as having or not having ASD” (Pediatrics, Sept 2011). An ASD classification required receiving a clinical diagnosis from an expert clinician not just a simple observation.
The results “show a total of 18.7% of the infants developed ASD. Infant gender and the presence of >1 older affected sibling were significant predictors of ASD outcome, and there was an almost threefold increase in risk for male subjects and an additional two fold increase in risk if there was >1 older affected sibling. The age of the infant at study enrollment, the gender and functioning level of the infant's older sibling, and other demographic factors did not predict ASD outcome” (Pediatrics, Sept 2011)
This study suggests the recurrence rate of ASD is higher than suggested by previous estimates. In my clinical experience I do see some risk factors and ASD outcomes among families. I often see families that have higher functioning children and once the sibling addition has been made many times that youngest child will exhibit symptoms earlier and more severe than their sibling. This may be in part because parents know what to look for with the new child and have more experience than with the first born. The new genetic technologies available to families allow them to test the child and themselves to see what the genetic percentage is of having another child with the same issues, although about half the families pass on this option. It’s nice to have options even if they do not fall into your philosophical beliefs.
Reference: PEDIATRICS Vol. 128 No. 3 September 1, 2011, pp. e488 -e495