the primary caregiver, (ii) was diagnosed with a pervasive developmental disorder, (iii) displayed significant signs of developmental delay, or (iv) had a coexisting medical, neurological, or genetic disorder. Families were ascertained from two collection sites: Duke University Medical Center, North Carolina and University of North Carolina, Greensboro, North Carolina. All participating family members provided written informed consent that had been approved by both institutional review boards.
