MedicalResearch.com:  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 MedicalResearch.com: 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.