Early Behavioral Indices of Inherited Liability to Autism

Recent developmental studies have indicated that autism spectrum disorder (ASD) may arise from critical combinations of specific early neurobehavioral susceptibilities, each of which may be traceable to partially-independent sets of genetic variation. These susceptibilities and their respective genetic origins may not relate to the characterizing symptoms of ASD (after it develops) in a straightforward way. Furthermore, some of the contributory liabilities may not necessarily be specific to ASD, and may account for “missing heritability” in molecular genetic studies. Identifying common genetic variants linked to these underlying traits rather than to a diagnosis of ASD may account for a greater share of the population attributable risk for ASD, especially if autism represents a developmental consequence of earlier-interacting susceptibilities. To elucidate the early endophenotypic structure for the development of autism will require testing of a next generation of viable early phenotypic candidates in a manner that is epidemiologically rigorous, in which the distinction between ASD prediction in the general population and ASD prediction of autism recurrence (i.e. within families affected by ASD) is closely attended to, and in which the relationships between endophenotypic candidates are mapped and normed.