Early detection of autism spectrum disorders: From retrospective home video studies to prospective 'high risk' sibling studies

In the past decades, many studies have focused on identifying subclinical signs of ASD with different types of experimental designs and methods, both retrospectively and prospectively. The purpose of this narrative review is to present changes in methodology, from a historical point of view, highlighting the strengths and weaknesses of different research designs. Conclusions are drawn taking into account potentialities of prospective designs for the study of early predictors of ASD.