Marsha Markle, M.A., M. A., Ed.S.

The last two decades have seen an alarming increase in the number of children identified with autism spectrum disorders (ASD). The increase appears to be widespread across the United States, signaling an urgent public health alert. The frequency of autism now surpasses that of all types of cancer combined. Numbers of such proportion have been likened to an epidemic.

The research on this “epidemic” has been the source of much disagreement. Many studies have been conducted, some using data from parents, others using data from educational settings serving students with ASD. Different states have contributed statistics from a variety of other sources. While specific data are not identical from every source, it is hard to debate the fact that the numbers of children diagnosed with ASD, and thus the costs of serving them, are rising across time.

The most recent study was a collaborative effort of the Center for Disease Control (CDC), the Department of Health and Human Services, and the American Academy of Pediatrics. It is the first national study of autism incidence in the United States. The findings appeared in an issue of the CDC’s journal Morbidity and Mortality Weekly Report, published May 2006. According to these findings, autism now affects 1 in every 166 children born today. The most widely cited rate for autism 10 to 15 years ago was 1 per 2,000 to 2,500.

It has been argued that the ASD rate increase is due to better and broader identification and diagnosis of children and the pursuit of funding for special services for such children under the Individuals with Disabilities Education Act (IDEA). While this may account for some of the rate explosion, several investigators have analyzed the data and find that this reason is insufficient to explain the large increase.

The ASD rate began to rise in the 1980s. The fact that there was not sufficient incidence of autism to warrant a separate eligibility category for autism until 1991 contributes to the claim of a rapidly growing rate increase for ASD students in recent history. One review study, using 54 published reports, showed a ten-fold increase in autism rates from 1993 to 2003, from less than 3 per 10,000 children in the United States to more than 30 per 10,000 children in the 1990s. According to the CDC report, ASD now affects up to 1 in every 175 school-age children. (This figure increases to 1 in every 166 when considering all children.) Thus, over 300,000 school-age children were diagnosed with autism in 2003–2004, when the study was conducted. The new national estimates from by the CDC echo reports from doctors and teachers and confirm the rate increase concerns.

In comparison with the estimated 300,000 affected students of 2004 reported by the CDC, the estimates were fewer than 95,000 in 2000, fewer than 115,000 in 2001, and fewer than 140,000 in 2002. These numbers are not influenced by a change in diagnostic definitions because the definitions have been consistent during that period of time. These annual growth rates are considered valid because they come from the same source, were calculated using the same methods and same definition, and are from a reliable government agency.

Cost estimates underscore the concern for the growing number of children affected by ASD. Consider the cost of caring for and educating a child with ASD. As of May 2006, the U.S. annual economic cost was estimated to be almost $6,500,000,000, including education and health care. This trend is alarming to educators and public health officials.

Naturally, when a trend affects so many families, school systems, and health systems, people want to know the causes. There is substantial controversy over the reason for the growing number of cases of autism. Studies in the United States and Great Britain continue to present conflicting data about environmental influences and genetic factors. Until the cause or causes are determined, and a reasonable intervention can be developed, the increase in the number of children diagnosed with ASD will remain a serious public health concern.

Explanations for the autism rate increase are controversial and include:

• Legal changes in IDEA. Until 1991 autism was never tracked by school systems and students with autistic characteristics may have been placed in special services under different categories.
• Vaccines. The CDC states that there is no connection between the thimerosal found in the Mumps-Rubella-Measles vaccine and autism rates, but parent advocacy groups do claim a connection exists.
• Environmental Concerns. Worries surround the contribution of toxins, mercury and nuclear waste to the rate of autism.