On the Autistic Spectrum Disorder concordance rates of twins and non-twin siblings.

Using the Interactive Autism Network Research Database, the Autistic Spectrum Disorder concordance rates for twins and non-twin siblings were calculated. For males, females and both genders together, the concordance rate for dizygotic twins is approximately twice that of non-twin siblings. We also determined that the concordance rate for non-twin siblings decreases as the interval between pregnancies increases. Our results appear to indicate that the uterine environment may contribute to autism concordance rates.