Nearly 1 in 100 American 8-year-olds struggle with autism, Asperger's syndrome or a related developmental problem, according to a new study. The estimate is the highest to date of so-called autism spectrum disorders from the Centers for Disease Control and Prevention, which tracks health trends. The spectrum includes a range of disorders, from severe autism to milder forms like Asperger's to "pervasive developmental disorder," a nonspecific diagnosis given to many children with social difficulties or some kinds of learning and sensory problems. The finding is based on an analysis of medical and school records of some 400,000 children around the country; the researchers did not meet or interview the children. Prevalence estimates for these disorders have increased so sharply in recent years—to 1 in 150 in 2007, from 1 in 300 in the early 2000s—that scientists have debated whether in fact the disorder is more common, or diagnosed more often as a result of higher awareness.