Autism Epidemic? Medscape article

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Autism " Epidemic? " : A Newsmaker Interview With Morton Ann

Gernsbacher, PhD, And Craig J. Newschaffer, PhD

Laurie Barclay, MD;

Medscape Medical News 2005. © 2005 Medscape

July 15, 2005 — Editor's Note: Despite heightened media attention on

the autism " epidemic, " a report published in the July issue of

Current Directions in Psychological Science offers three arguments

against a true increase in autism prevalence. These include changes

in diagnostic criteria for autism, with current criteria being more

inclusive than when the diagnosis was first defined in the 1940s;

methodological flaws in an unpublished California study widely cited

as showing dramatically increased prevalence; and problems in using

the U.S. Department of Education's annual " child count " data.

To find out more about this issue and its clinical implications,

Medscape's Laurie Barclay interviewed lead author Morton Ann

Gernsbacher, PhD, a Vilas Research Professor, the Sir Frederic

Bartlett Professor at the University of Wisconsin-Madison, and

President-Elect of the American Psychological Society.

For an alternate viewpoint, Dr. Barclay also interviewed Craig J.

Newschaffer, PhD, an associate professor of epidemiology at the

Center for Autism and Developmental Disabilities, s Hopkins

Bloomberg School of Public Health in Baltimore, land. Dr.

Newschaffer is lead author of a study using cohort curves to suggest

that autism prevalence has been increasing with time, as reported in

the March issue of Pediatrics.

Medscape: What is the evidence supporting an autism " epidemic? "

Dr. Gernsbacher: The evidence that is often used to support the

notion of an " autism epidemic " is the changing prevalence rates

across time, according to epidemiological data, and the increasing

number of individuals being served; for example, the increasing

number of children being served by the public schools under the

Individuals with Disabilities Education Act.

Dr. Newschaffer: There is no doubt that numbers of children with an

autism diagnosis or special education label has increased

tremendously over the past two decades. These numbers are clearly

beyond what we would have anticipated using historical estimates of

autism prevalence. The real question is what proportion of this

increase is attributable to a real change in the risk of autism and

what proportion is attributable to changes in diagnosis/labeling

tendencies.

Medscape: Why should we be cautious about this label, given changes

in diagnostic criteria and in heightened awareness and recognition

of this condition?

Dr. Gernsbacher: One thing that some people fail to realize is there

were no standard diagnostic criteria for autism in the Diagnostic

and Statistical Manual (of the American Psychiatric Association),

the DSM, until 1980, and the criteria in the DSM have undergone

purposeful change during the past 25 years. Therefore, any estimates

of the prevalence of autism prior to 1980 would have been based on

individual clinicians' or specific researchers' definitions, and

would have fluctuated because of factors that continue to introduce

variation into current-day estimates, such as variation in the size

of the population sampled and the manner of identification.

Estimates since 1980 would have been based on changing versions of

the DSM criteria.

Another thing that some people fail to realize is that increases in

the usage of services is not always a good metric for prevalence.

There can be a myriad of reasons why more individuals are using

services at one point in time than another, independent of how many

individuals qualify for those services.

Dr. Newschaffer: The formal definition of the term " epidemic " is

surprisingly loose. However, this term should be reserved for

situations where a higher-than-anticipated increase in case number

is believed to be attributed to a shift in the real risk of the

disease occurring.

For autism, unfortunately, this is difficult to determine.There are,

on one hand, serious challenges to developing good quality

scientific evidence supporting a hypothesis of " real risk increase "

and also serious challenges to developing an evidence base

supporting a " diagnostic/labeling practice change " hypothesis. It is

hard to test the hypothesis of real risk because specific risk

factors for autism are largely unknown. It is also difficult to

develop good studies testing hypotheses related to

diagnostic/labeling changes because the autism diagnosis is

behaviorally based – for example, studies of diffusion of hard

diagnostic technology are not relevant here.

I believe that there currently is little strong evidence supporting

either hypothesis (real risk versus diagnostic bias) and that

proponents of one versus another hypothesis seem to hold their view

based mainly on the basis of beliefs that are fallacious – either

that the increase has been so large [that] some of it has to be

real, or that the heritable component of autism is so large [that]

the increase over time must be due to diagnostic changes.

Medscape: What are the significant changes in diagnostic criteria

for autism between 1980 and 1994?

Dr. Gernsbacher: Whereas the 1980 DSM-III entry required satisfying

six mandatory criteria, the more recent 1994 DSM-IV offers 16

optional criteria, only half of which need to be met. Moreover, the

severe phrasing of the 1980 mandatory criteria contrasts with the

more inclusive phrasing of the 1994 optional criteria. For instance,

to qualify for a diagnosis according to the 1980 criteria, an

individual needed to exhibit ''a pervasive lack of responsiveness to

other people. " In contrast, according to 1994 criteria, an

individual must demonstrate only ''a lack of spontaneous seeking to

share.... achievements with other people'' and peer relationships

less sophisticated than would be predicted by the individual's

developmental level. The 1980 mandatory criteria of ''gross deficits

in language development'' and ''if speech is present, peculiar

speech patterns such as immediate and delayed echolalia,

metaphorical language, pronominal reversal'' were replaced by the

1994 options of difficulty ''sustain[ing] a conversation'' or ''lack

of varied ...social imitative play. " ''Bizarre responses to various

aspects of the environment'' became ''persistent preoccupation with

parts of objects. "

Furthermore, whereas the earlier 1980 (DSM-III) entry comprised only

two diagnostic categories (infantile autism and childhood onset

pervasive developmental disorder), the more recent 1994 (DSM-IV)

entry comprises five. Three of those five categories connote what is

commonly called autism: Autistic Disorder, Pervasive Developmental

Disorder Not Otherwise Specified (PDDNOS), and Asperger's Disorder.

Autistic Disorder requires meeting half of the 16 criteria, but

Asperger's Disorder, which did not enter the DSM until 1994,

involves only two thirds of that half, and PDDNOS, which entered the

DSM in 1987, is defined by subthreshold symptoms. Therefore,

Asperger's Disorder and PDDNOS are often considered ''milder

variants.'' These milder variants can account for nearly three

fourths of current autism diagnoses, as shown by Chakrabarti and

Fombonne in 2001.

Dr. Newschaffer: Formal changes in diagnostic criteria over this

time period include the shift from the DSM-III criteria introduced

in 1980 to the DSM-III-R criteria, introduced in 1987, and then the

move to the DSM-IV in 1994. The DSM-III-R was seen as perhaps too

broad an expansion of diagnostic criteria for what was referred to

as " infantile autism " in the DSM-III (referred to as " autistic

disorder " in DSM-III-R and beyond). The DSM-IV included a conscious

effort to rein back on the DSM-III criteria but also added new

categories (Asperger's syndrome, and PDDNOS) for other pervasive

developmental disabilities phenotypes similar to but not meeting

criteria for autistic disorder.

Medscape: What do you believe was the impetus behind making the

diagnostic criteria less restrictive?

Dr. Gernsbacher: I believe the effort was to better identify

individuals who truly needed services and support but were not

receiving them before.

Dr. Newschaffer: The recognition that the autism phenotype was in

fact broader than it was believed to be in 1980.

Medscape: What is the significance of the unpublished California

study claiming to show that these new criteria did not contribute to

the increased number of California cases diagnosed from the 1980s to

the 1990s, and, Dr. Newschaffer, of your study in the March issue of

Pediatrics?

Dr. Gernsbacher: A strength of the [California] study is the effort

to understand the changing prevalence rates.

Dr. Newschaffer: The California study provides little reliable

evidence. Our study offers weak to moderate evidence against a

fairly restricted hypothesis – that there has been a major increase

in the tendency to use the autism category for kids who formally

would have been classified under other special education categories.

Medscape: What, if any, are the limitations of the California study

and of its authors' conclusions?

Dr. Gernsbacher: A great limitation is that the study used only

current-day and putatively broader diagnostic criteria to assess

whether there had been any changes in diagnostic criteria from the

1980s to the 1990s. As I mentioned before, the standard diagnostic

criteria changed quite dramatically from the 1980s to the 1990s, so

it would have been odd if the criteria used to qualify Californians

for services did not also change during that time. A better design

for the California study would have been if they had used two sets

of criteria: those used in the current day and those that were used

previously. If they then would have applied both sets of criteria to

both groups of children (those served in the 1980s and those served

in the 1990s), they would have had a more authentic way of

discerning whether the criteria have changed or not.

Dr. Newschaffer: Both studies [the California study and our

Pediatrics study] illustrate how difficult it is to acquire good

data to support or refute a hypothesis that diagnostic/labeling

phenomenon explain the increases witnessed over recent years. The

California study was retrospective in design and thus vulnerable to

recall biases – mothers of children diagnosed 10 years previously

needed to recall behaviors at time of diagnosis. It also suffered

from poor participation rate, less than 20%, making it also very

vulnerable to selection bias. Our Pediatrics paper presented an

analysis of administrative data – always a data source [that] must

be viewed cautiously when trying to learn something about real risk.

Our analysis suggested that children previously classified in other

special education categories were not being shifted wholesale into

the autism category. However, our analysis was a group level, not an

individual level, comparison and had no ability to see whether there

are children who formerly would not have received a special

education classification at all that are now receiving an autism

classification.

Medscape: Please comment on whether or not the U.S. Department of

Education's annual " child count " data can be used as supportive

evidence of an autism epidemic.

Dr. Gernsbacher: Three serious drawbacks to using the U.S.

Department of Education's annual " child count " data as support for a

so-called " autism epidemic " are first, that the data are a count of

only the children served, not of all the children who meet

diagnostic criteria. If a child does not need special education

services, he will not be represented in the child count. Second, the

criteria for which children will receive services vary from state to

state and across time. Third, and perhaps most overlooked, the child

count data for autism only began to be collected after the school

year 1991-92.

Many states report in their annual report to Congress that they are

still revising their identification and reporting policies. For

example, from 1992 to 2001, the state of Massachusetts reported the

lowest percentage of children with autism of any state. Then, in

2002, Massachusetts reported a 400% increase in just one year! Why?

Because that is when Massachusetts began actually counting the

students with autism that were served rather than simply applying a

ratio to the total population – a ratio that had been calculated way

back in 1992. In their 2002 IDEA report to Congress, Massachusetts

state officials warned that the increase will continue for several

years as ''[school] districts better understand how to submit their

data at the student level'' (IDEA, 2002, p. 4) and as ''all

districts comply completely with the new reporting methods'' (IDEA,

2002, p. 4).

Dr. Newschaffer: Administrative data like this can never be a

definitive source on real risk changes. However, these data can be

used to explore certain questions related to classification

tendencies.

Medscape: Independent of loosened diagnostic criteria and heightened

public awareness, are there any biological reasons to suspect the

true incidence of autism could be increasing, and if so, what are

they?

Dr. Gernsbacher: Because we do not have validated biological markers

for autism, there is nothing to track for an increase other than the

behaviorally based diagnostic formulations.

Dr. Newschaffer: If the true risk of a condition increases over a

short time period, that implies that there have been changes in

nonheritable risk factors, because shifts in genetic risk factors

take generations to have perceptible impacts on risk trends. So, if

real risk changes are driving all or a substantive part of the

recent secular trend in [autism spectrum disorder] ASD, there must

be important nonheritable determinants, also known as environmental

determinants, of ASD, and these determinants must have changed

drastically over time. Because we know so little about the etiologic

mechanism underlying ASD, we have no solid leads as to what these

determinants might be. I do think that even if there had not been

the increases in reported rates of ASD, the fact that all of the

genetic research on ASD has suggested very complex mechanisms, this,

in itself, increases the likelihood that environmental factors are

involved. Also, please remember that in this context the

term " environmental " refers to anything other than genes – this, of

course, includes chemicals, but also includes things like diet and

stress.

Medscape: What, in your opinion, are the benefits and potential

harms of the new criteria?

Dr. Gernsbacher: The benefits are identifying individuals who are in

need of services and support and supplying those necessary services

and support. A potential harm is if other persons – for example,

parents or other members of the community – become very worried that

their children are " doomed " because they have been identified or

diagnosed. I believe that the earlier a parent realizes that his or

her child might be developing atypically, the earlier that parent

can meet the child's needs and structure the child's environment to

capitalize on the child's unique strengths.

Autism intervention research is still in its early stages. We simply

do not know with any scientific certainty what types of

interventions, in what combinations or sequences, are useful,

necessary, or even possibly contraindicated, or how to fit

particular services and support to different individuals.

Dr. Newschaffer: The heightened awareness of ASDs, in part related

to shifts in perception of the phenotype, is what is really driving

the push for early detection. There is clear evidence supporting the

effectiveness of early, behaviorally based interventions, but there

is much need for continued work in order to determine, for example,

best intervention practices for different ASD subtypes. If you were

to compare the depth and richness of the evidence already

accumulated for ASD intervention compared to that for, say,

hypertension, the contrast would be striking.

I think that experienced clinicians make very effective use of

recent criteria. However, as we push for more and broader screening

for ASDs, there are increasing chances that more children without

ASDs will, at least, be flagged for follow-up assessments. It is

imperative that resources be available to allow these screen-

positive children to receive thorough diagnostic follow-up. There

has been some research suggesting that children identified as

potentially having ASDs (through brief parental interview tools that

can be used in screening efforts) who are not confirmed as ASD cases

still could potentially benefit from more intensive follow-up

services. However, I think we need to monitor this very carefully as

ASD screening initiatives gain ground.

Medscape: What suggestions do you have for future research in this

area?

Dr. Gernsbacher: We clearly need a better understanding of how many

adults with autism there are in our communities. It is possible that

many of these individuals were not identified when they were

younger, and it is possible that their needs are still not being met

sufficiently.

Dr. Newschaffer: Part of the initial strategy in the start of

the " War on Cancer " several decades ago was to put in place a

national monitoring system that could accurately track trends in

cancer incidence. This was accomplished with the establishment of

state cancer registries and the Surveillance Epidemiology and End

Results (SEER) program at [the National Cancer Institute] NCI. The

data generated by these efforts have been invaluable in helping us

to understand the forces behind changes in trends of various cancers

(ranging from pediatric brain cancer to prostate cancer). A similar

effort needs to be established for ASDs (and other developmental

disorders). The CDC has begun this with its creation of the Autism

and Developmental Disorders Monitoring (ADDM) network.

However, there are a number of special challenges faced by this, or

other similar initiatives, focusing on ASDs. First, concerns of

privacy protection have made it increasingly difficult for public

health projects focusing on monitoring disease occurence in full

population samples to gain ground. We in public health have to

redouble our efforts explaining why these programs are crucial.

Second, because of the behavioral nature of the ASD diagnosis, in

addition to monitoring prevalence using standard case definitions,

we need to do more: either concurrently validate disgnoses in

samples of subjects through direct observation, and/or find a way to

monitor diagnostic tendencies among clinical and educational

practitioners. All of these efforts are nontrivial in terms of

resources needed and methodological and logistical challenges to be

surmounted.

Medscape: Is there anything you would like to add?

Dr. Gernsbacher: I want to stress that the conclusion to our article

stated strongly the following: " Realizing that the increasing

prevalence rates are most likely due to noncatastrophic mechanisms,

such as purposely broader diagnostic criteria and greater public

awareness, should not, however, diminish societal responsibility to

support the increasing numbers of individuals being diagnosed with

autism. Neither should enthusiasm for scientific inquiry into the

variety and extent of human behavioral, neuroanatomical, and

genotypic diversity in our population be dampened. "

Disclosures: Dr. Gernsbacher has throughout her career received

funding from the National Institutes of Health, the National Science

Foundation, the Army Research Institute, and the Air Force Office of

Sponsored Research. She is also currently an investigator on a grant

titled " Wisconsin Autism and Other Developmental Disability

Surveillance, " sponsored by the Centers for Disease Control.

Dr. Newschaffer's Center receives support from NIH, CDC, and NAAR

(National Alliance for Autism Research) and participates in the ADDM

network.

Current Directions in Psychological Science.2005;xxx-xxx

Pediatrics.2005;115(3):e277-82

Reviewed by D. Vogin, MD

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