Two Autism Controversies

David Douglass, Ph.D.

ONE: "There is an autism epidemic."
Members of the general public may be surprised to learn this claim is controversial.

In 2002, prominent news organizations and members of the U.S. Congress reported an "upsurge," an "outbreak," or an "epidemic" of cases of autism. Since then, it is true the Centers for Disease Control (CDC) raised their estimate of the number of cases nationwide, from 1/150 children (2002) to 1/110 children (2006).
It also is true that the CDC (2011) says, "It is unclear how much of this increase is due to a broader definition of ASDs and better efforts in diagnosis. . . . By studying the number of people diagnosed with an ASD over time, we can find out if the number is rising, dropping, or staying the same." One possible explanation for the changing numbers is a real increase in the number of people with autism, but a team of experts (Gernsbacher et al., 2005) offered other explanations.

More people are being counted

The diagnosis of autism is based on observation of behaviors. As with almost all mental disorders, there is no physical test that produces reliable results. Most practitioners use the diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association, which has been revised several times. In 1980, the DSM-III criteria for autism were six mandatory features. In 1994, the DSM-IV criteria were much looser: 4 of 8 features in group A, plus 4 of 8 features in group B. Also, the strict wording used for some of the features in DSM-III was replaced by broader, more inclusive wording in DSM-IV.

Gernsbacher et al. (2005) offered this analogy:
"Suppose the criterion for ‘‘tall'' was 74.5 in. and taller in the mid-1980s, but the criterion was loosened to 72 in. and taller in [1994] . . . census data allow us to estimate that 2,778 males in McClennan County, Texas would be called tall by the more restricted 74.5-in. criterion, and 10,360 males would be called tall by the
broader 72-in. criterion . . . without any real increase in Texans' height."

Recently, other teams of researchers examined more data and reached the same conclusion: the change in diagnostic criteria explains much of the increase in the number of autism cases reported (Matson & Kozlowski, 2011; Saracino et al., 2010).

More people are counting

In 1991, the Individuals With Disabilities Education Act (IDEA) became law. One of the requirements is that each year the schools report to the Department of Education a count of the number of children with disabilities being served. Before this law, there was no nationwide count of students with autism.

With any change in education practices, some schools adopt the changes faster than other schools. Also, complete changes are not made overnight; they occur gradually over several years as teachers and administrators learn the rules and spot flaws in their procedures. The counting of students with autism began unevenly and took several years to be implemented fully across the country.
So, the counts in the early 1990s were too low and, gradually, they came closer to the estimates based on large epidemiological studies. When measuring anything, if we start with numbers that are artificially low, the numbers will get higher.

Gernsbacher et al. (2005) offered these examples:
"Consider another IDEA reporting category introduced along with autism in 1991–1992: ‘traumatic brain injury.' From 1991–1992 to 2000–2001, this category soared an astronomical 5,059%. Likewise, the reporting category ‘developmental delay,' which was introduced only in 1997–1998, grew 663% in only 3 years."

In 2011, most researchers agree that some of the increase in autism cases is due to changes in diagnostic and reporting procedures, but there is some debate about the size of this effect. Don't expect this issue to be resolved soon. The 2011 draft of autism criteria for DSM-5 include more changes and (in my opinion) increased ambiguity. A safe bet is that the number of reported cases will continue to bounce around.

TWO: "Vaccines increase the risk of developing autism."
This claim has sparked many headlines in many countries. In 1998, British physician Andrew Wakefield and 12 colleagues published a report that alleged to show a relationship between autism and the vaccine for measles-mumps-rubella (MMR). Typically, the first dose of the MMR vaccine is administered at the age of 15 to 20 months. Because many autistic symptoms become obvious around 24-30 months of age, many parents may be tempted to believe that the MMR is a trigger for autism. In 2004, 10 of the paper's 13 authors (but not Wakefield) said that it's conclusions were unwarranted, and later The Lancet, the journal that published the paper, retracted it.

Problems with the Wakefield study

First, the researchers looked at only 12 children, all of whom were diagnosed with autism. Using such a small sample to draw general conclusions was unreasonable. Failing to include a control group of non-autistic children was at least sloppy and perhaps an attempt to skew the results. Second, medical records show that 5 of the 12 children displayed symptoms of abnormal development before they were given the MMR vaccine. This fact was not included in Wakefield's paper.

Other results don't fit

Several groups of researchers have examined data sets much larger than Wakefield's and found no relationship between autism and the MMR. For example:

Among children born between 1980 and 1994, the increased rate of MMR vaccination in California does not correlate with the increased rate of autism diagnoses in California (Dales et al., 2001).

Among all the children born in Denmark from 1991 to 1998 (over half a million), researchers found no difference in the rate of autism for children with or without the MMR (Hviid et al., 2003).

In 2004, a group of researchers reviewed the results of 14 studies and found no relationship between autism and the MMR. This group was assembled by the Institute of Medicine, an organization free of government funding that advises the federal government on health matters. The head of this review, Dr. Marie McCormick of the Harvard School of Public Health, stated that the researchers were not paid and had no ties to vaccine makers or to the government.

The story changes

As the failures to link autism and the MMR multiplied, some people suggested a new theory: the MMR was not inherently harmful but a vaccine preservative, thimerosal, could trigger autism. Researchers gathered more data, including large samples of American children, and found no link between autism and thimerosal (Doja & Roberts, 2006; Price et al., 2010).

Some minds have changed

Researchers at the M.I.N.D. Institute (at UC Davis) took seriously the idea that the MMR, or the preservative thimerosal, could cause autism. In 2007, however, they posted the following on their website:
"The M.I.N.D. Institute is committed to an open-minded approach that supports research on a broad spectrum of factors that might lead to autism. . . current research and knowledge does not suggest that vaccines are a cause of autism spectrum disorders, and that vaccinations in healthy children are safe and very important in preventing the re-emergence of epidemics of infectious diseases that have killed millions of people in the past."

Unethical behavior?

With remarkable foresight, a columnist in Scotland predicted: "Wakefield will emerge as a martyred hero, a brave and lonely warrior waging battle against the conspiratorial medical profession" (DeGroot, 2004).

Wakefield failed to disclose that he was paid by an organization that was trying to show a link between autism and the MMR vaccine so that they could file suits against the vaccine makers. Beginning two years before his paper was published, Wakefield was paid more than $700,000 (Deer, 2011).

In May 2010, British medical officials revoked Andrew Wakefield's license to practice. (After the controversy started, he moved to the United States. He continues to deny all of the charges of misconduct.)

REFERENCES

Centers for Disease Control and Prevention (2011). Autism spectrum disorders (ASDs) http://www.cdc.gov/ncbddd/autism/research.html

Deer, B. (January 5, 2011). How the case against the MMR vaccine was fixed. British Medical Journal. DOI: BMJ 2011; 342:c5347

DeGroot, G. (February 29, 2004). Autism is a mystery, not a medical conspiracy. http://scotlandonsunday.scotsman.com/opinion.cfm?id=237982004

Doja, A, & Roberts, W. (2006). Immunizations and autism: A review of the literature. Canadian Journal of Neurological Science. 33, 341–346.

Gernsbacher, M.A., Dawson, M & Goldsmith, H. H. (2005). Three reasons not to believe in an autism epidemic. Current Directions in Psychological Science, 14. 55-58.

Hviid, A., Stellfeld, M., Wohlfahrt, J. & Melbye, M. (2006). Association between thimerosal-containing vaccine and autism. JAMA: Journal of the American Medical Association, 290, 1763-1766.

Dales, L., Hammer, S. J. & Smith, N. J. (2001). Time trends in autism and in MMR immunization coverage in California. JAMA: The Journal of the American Medical Association, 285, 1183-1185.

Matson, J. L. & Kozlowski, A. M. (2011). The increasing prevalence of autism spectrum disorders. Research in Autism Spectrum Disorders, 5, 418-425.

M.I.N.D. Institute (2007). Vaccines, Thimerosal and Other Potential Environmental Causes of Autism. http://www.ucdmc.ucdavis.edu/mindinstitute/newsroom/vaccineposition.html

Price, C. S., Thompson, W. W., Goodson, B. Weintraub, E. S., Croen, L. A., Hinrichsen, V. L., Marcy, M., Robertson, A., Eriksen, E., Lewis, E., Bernal, P., Shay, D., Davis, R. L. & DeStefano, F. (2010). Prenatal and infant exposure to thimerosal from vaccines and immunoglobulins and risk of autism. Pediatrics published online Sep 13, 2010, DOI: 10.1542/peds.2010-0309

Saracino, J., Noseworthy, J., Steiman, M., Reisinger, L. & Fombonne, E. (2010). Diagnostic and assessment issues in autism surveillance and prevalence. Journal of Developmental and Physical Disabilities, 22, 317-330.