The number of American children with learning and developmental disabilities has been climbing over the past decade, reaching nearly one in six by 2008. The increasing prevalence of autism and attention deficit hyperactivity disorder accounts for most of this change.The National Academy of Sciences estimates that combinations of environmental factors, including exposure to toxic chemicals, along with genetic susceptibility, cause or contribute to at least 25% of learning and developmental disabilities in American children.
Intellectual disability (formerly referred to as mental retardation) affects 2%, or approximately 1.4 million, children in the United States. As of 2009, 9% of children—roughly 50 million kids—were diagnosed with attention deficit hyperactivity disorder (ADHD). According to the U.S. Centers for Disease Control and Prevention (CDC), an estimated 1 in 88 children in the United States have an autism spectrum disorder. Between 1997 and 2008, the prevalence of autism increased nearly 300% nationally. In a seminal study of California’s dramatic rise in autism rates, researchers found that about 30% of the rise could not be explained by changes in the age of diagnosis or the inclusion of milder cases. (more…)