Stability of diagnostic assessment for autism spectrum disorder between 18 and 36 months in a high‐risk cohort

Children with autism spectrum disorder (ASD) are diagnosed, on average, around the age of 4 years. However, previous research has shown that the diagnosis can be made as early as 2 years, and that if the child is seen a year or more later, it is highly likely that the diagnosis will be confirmed. In this study, to examine whether diagnoses made as early as 18 months of age are also "stable," we followed a group of younger siblings of children …