(HealthDay News) – The overall relative recurrence risk for autism spectrum disorders (ASDs) is 6.9, with significant risks seen for maternal and paternal full-siblings and for maternal half-siblings, according to a study published online Aug. 19 in JAMA Pediatrics.
Therese K. Grønborg, from Aaarhus University in Denmark, and colleagues conducted a population-based study using data from all children born in Denmark from January 1980–December 2004, who were followed through December 2010, to estimate the relative recurrence risk for ASDs. A maternal sibling sub-cohort derived from mothers with a least two children was identified, as was a paternal sibling sub-cohort. The risk of having ASD was compared for children with vs. those without an older sibling with ASD.
The researchers found that the overall relative recurrence risk was 6.9, with no significant changes observed over time. The risks were similar for maternal and paternal full siblings. For maternal half-siblings, the relative recurrence risk was 2.4 (95% confidence interval, 1.4–4.1), while for paternal half-siblings it was 1.5 (95% confidence interval, 0.7–3.4).
“Although the results from our comparison of recurrence in full- and half-siblings support the role of genetics in ASDs, the significant recurrence in maternal half-siblings may support the idea of a contributing role of factors associated with pregnancy and the maternal intrauterine environment,” the authors write.