Continuing Increases in Autism Reported to California's Developmental Services System

Abstract
Diagnosed cases of autism spectrum disorders (ASD) have increased in recent decades.1-3 The extent to which this increase reflects changes in occurrence, case definition, recognition, or referral patterns of ASD is the subject of vigorous debate. Young children receive immunizations in the period preceding the typical manifestations or diagnosis of ASD. Increased exposure to thimerosal, a preservative that contains 49.6% ethylmercury by weight, has been postulated to have contributed to the upswing in reported cases of ASD.4,5