California's autism rate has skyrocketed over the past four years according to a new study recently completed by the state's Department of Developmental Services. According to the report, which tracked the number of autism cases reported to 21 regional medical centers receiving government-funded aid, 10,360 cases were recorded in December 1998, with that number increasing to 20,337 in 2002.

Health officials and public interest groups are continuing to debate the cause of the occurrence, which a recent parallel study conducted by researchers with the UCLA Neuropsychiatric Institute claimed was not due to population or reporting changes. The 97 percent increase doubles the rises seen in epilepsy, cerebral palsy and mental retardation cases during the same period according to the study's authors.

Although highly controversial, many parents in the state believe vaccines containing the mercury-based preservative thimerosal led to their children's development of autism. Medical experts have linked mercury exposure to the disorder in children.