The quantitative comparison of IDEA snapshot and constant-age tracking trend slopes suggests that ~75-80% of the tracked increase in autism since 1988 is due to an actual increase in the disorder rather than to changing diagnostic criteria.
These estimates suggest that at least part of the increase in autism diagnoses, about 50–65%, reflects an increase in the true prevalence of the disorder. (JEL L11, J2, J3)
Results suggest that among professional psychologists with a terminal degree (n=88), the majority believe that diagnostic changes can not fully account for the observed increase; 72% reported wither the true rate may have, or definitely has, increased
Published in the January 2009 issue of the journal Epidemiology, results from the study also suggest that research should shift from genetics to the host of chemicals and infectious microbes in the environment that are likely at the root of changes in the neurodevelopment of California’s children.