EDITORIAL PREFACE The Very Early Autism Phenotype Nurit Yirmiya Æ Sally Ozonoff Published online: 12 January 2007 Ó Springer Science+Business Media, LLC 2007 Keywords Early Autism Phenotype Introduction In this editorial preface, we first describe the historical roots of this special issue. We then introduce the papers, all of which focus on the very early phenotype of autism and the broad autism phenotype. Some of the papers in this volume include studies on the very youngest children diagnosed with Autism Spectrum Disorders (ASD), 1 while in other papers the focus is on infant siblings of children with autism. Next, we discuss some methodological and clinical issues pertaining to the studies. We end by considering the ethics involved in these kinds of studies, their implications for preven- tion and intervention, and possible future directions. Historical Roots In the mid-1980s, Marian Sigman, while on sabbatical in Europe, spoke with Sir Michael Rutter and Simon Baron-Cohen about initiating a young siblings study in order to achieve insight into the early precursors of autism. At that time, before the publication of the ADI-R and ADOS, Sir Michael Rutter was concerned that the older siblings with autism would not be diagnosed similarly across sites (and countries) and thus the group decided not to pursue this interest at that time. However, in the early 1990s, after publica- tion of standardized diagnostic instruments that would make cross-site collaborations more reliable, Marian Sigman and Nurit Yirmiya initiated the first sibling study (Yirmiya et al., 2006; Yirmiya, Gamliel, Shaked, & Sigman, 2006) in collaboration with Simon Baron- Cohen and Christopher Gillberg, who also collected data in the UK and Sweden. At the time, autism was estimated to occur in about 5 in every 10,000 live births, and the recurrence rate of autism in families was estimated at 4–8%, i.e., almost 100 fold that of the general population. Children were then diagnosed most often around age 3 years or older. Thus younger siblings were the optimal at-risk group for those interested in lowering the age of diagnosis. The hope was that earlier identification would lead to earlier intervention and a better prognosis. Several research groups soon joined this research endeavour, leading to the establishment of the Baby Siblings Research Consortium (BSRC), a voluntary network of researchers studying infant siblings of children with autism and other very young children at risk for ASD. This consortium was first established in 2003 to bring together the major research groups in the N. Yirmiya (&) Department of Psychology and School of Education, The Hebrew University of Jerusalem, Mount Scopus, Jerusalem, Israel e-mail: NuritYirmiya@huji.ac.il S. Ozonoff Department of Psychiatry and Behavioral Sciences, MIND Institute, University of California Davis Medical Center, Sacramento, California, USA e-mail: sjozonoff@ucdavis.edu 1 In this paper, we use the term ASD to collectively refer to children meeting criteria for Autistic Disorder and Pervasive Developmental Disorder Not Otherwise Specified. When a distinction between these conditions is important, the specific term is used. J Autism Dev Disord (2007) 37:1–11 DOI 10.1007/s10803-006-0329-1 123