Mathilda’s Weird World Weblog

December 27, 2011

Autism, part one. Debunking the ‘autism epidemic’ with actual evidence

Filed under: conspiracy theory — Tags: , — mathilda37 @ 12:25 pm

I have a family member who is a conspiracy theory nut. Well, after having my ear bent about how ‘it’s all done to boost big pharma’s profits’, I decided to dig up all the available information I could and start addressing some of his fixations. Fixation one is autism and vaccines. Reading on the internet, I discovered some frighteningly poor sources of information, which he unfortunately has just accepted without checking the provenance of the info, or looking up anything else. Number one of the bad sites is ‘child health safety’. Which has made the hilarious but also dangerous claims that we don’t need vaccines any more. For a later post.

We have a severely autistic family member, which is where this all comes from. Speaking from personal experience, I have known five autistic boys; four of them have Asperger’s. Back in the eighties, four out of five of these children would never have had a diagnosis of ASD. And there’s an excellent chance the fifth would have been labelled as retarded and not autistic. I’ve chatted with numerous older teachers and a retired doctor, and their personal observations agree with mine. That a lot of children who would just have been called odd or naughty, are now getting diagnoses of  ASD.  In fact, four of the ASD children I’ve known seem normal to the untrained eye, and it’s taken specialists to diagnose them.

So I  decided to look up what studies I could find about the incidence and diagnosis of autism. So far, only one backs the idea that there has been a genuine increase in autism cases. I’m pasting the list below. Of course if you are a diehard paranoid conpiracist, you’ll think that all the evidence against an autism epidemic is faked by the drug companies. However, the better balanced among us will observe that the body of the evidence really isn’t supporting some massive increase.

Studies against a meaningful increase in autism incidence.

Autism and diagnostic substitution: evidence from a study of adults with a history of developmental language disorder. link

“Some children who would nowadays be diagnosed unambiguously with autistic disorder had been diagnosed with developmental language disorder in the past. This finding has implications for our understanding of the epidemiology of autism.”

Pervasive developmental disorders in preschool children: confirmation of high prevalence. link

The rate of pervasive developmental disorders is higher than reported 15 years ago. The rate in this study is comparable to that in previous birth cohorts from the same area and surveyed with the same methods, suggesting a stable incidence”

Epidemiology of autistic disorder and other pervasive developmental disorders. link

Epidemiology of Pervasive Developmental Disorders pdf

There is evidence that the broadening of the concept, the expansion of diagnostic criteria, the development of services, and improved awareness of the condition have played a major role in explaining this increase, although it cannot be ruled out that other factors might have also contributed to that trend. …. Although it is clear that prevalence estimates have gone up over time, this increase most likely represents changes in the concepts, definitions, service availability, and awareness of autistic-spectrum disorders in both the lay and professional public.

Epidemiology and possible causes of autism link

“A major cause of the recent large increase in the number of boys diagnosed with autism probably is due to changing diagnostic practices.”

Incidence of autism spectrum disorders: changes over time and their meaning. link

“The true incidence of autism spectrum disorders is likely to be within the range of 30-60 cases per 10 000, a huge increase over the original estimate 40 years ago of 4 per 10000. The increase is largely a consequence of improved ascertainment and a considerable broadening of the diagnostic concept. However, a true risk due to some, as yet to be identified, environmental risk factor cannot be ruled out. There is no support for the hypothesis for a role of either MMR or thimerosal in causation, but the evidence on the latter is more limited”

The Contribution of Diagnostic Substitution to the Growing Administrative Prevalence of Autism in US Special Education pdf

 Prevalence findings from special education data do not support the claim of an autism epidemic because the administrative prevalence figures for most states are well below epidemiological estimates. The growing administrative prevalence of autism from 1994 to 2003 was associated with corresponding declines in the usage of other diagnostic categories.

Vaccines and the changing epidemiology of autism. link

“The recorded prevalence of autism has increased considerably in recent years. This reflects greater recognition, with changes in diagnostic practice associated with more trained diagnosticians; broadening of diagnostic criteria to include a spectrum of disorder; a greater willingness by parents and educationalists to accept the label (in part because of entitlement to services); and better recording systems, among other factors. The cause(s) of autism remains unclear. There is a strong genetic component which, along with prenatally determined neuro-anatomical/biochemical changes, makes any post-natal ’cause’ unlikely.”

The validity of the autism spectrum disorders-diagnosis for intellectually disabled adults link

Prevalence of autism and related conditions in adults in a mental handicap hospital. link

Epidemiology of Autism Spectrum Disorders in Adults in the Community in England link

“To our knowledge, there is no published information on the epidemiology of autism spectrum disorders (ASDs) in adults. If the prevalence of autism is increasing, rates in older
Conclusions  Conducting epidemiologic research on ASD in adults is feasible. The prevalence of ASD in this population is similar to that found in children. The lack of an association with age is consistent with there having been no increase in prevalence and with its causes being temporally constant.”

Three Reasons Not to  believe in an Autism Epidemic link

ABSTRACT—According to some lay groups, the nation is experiencing an autism epidemic—a rapid escalation in the prevalence of autism for unknown reasons. However, no sound scientific evidence indicates that the increasing number of diagnosed cases of autism arises from anything other than purposely broadened diagnostic criteria, coupled with deliberately greater public awareness and intentionally improved case finding. Why is the public perception so disconnected from the scientific evidence? In this article we review three primary sources of  misunderstanding: lack of awareness about the changing diagnostic criteria, uncritical acceptance of a conclusion illogically drawn in a California-based study, and inattention to a crucial feature of the ‘‘child count’’ data reported annually by the U.S. Department of Education.

Increase in autism due to change in definition, not MMR vaccine link

Social Influence Plays Role in Surging Autism Diagnoses, Study Finds (can’t locate paper)

the study, by researchers from the Institute for Social and Economic Research and Policy at Columbia University, found that children living near a child who has been previously diagnosed with autism have a much higher chance of being diagnosed themselves in the following year. The increased likelihood of being diagnosed is not due to environmental factors or contagious agents, the study found. Rather, it is due mainly to parents learning about autism from other parents who have a child diagnosed with the disorder.

The Changing Prevalence of Autism in California pdf

These data suggest that improvements in detection and changes in diagnosis account for the observed increase in autism; whether there has also been a true increase in incidence is not known.

Analysis of prevalence trends of autism spectrum disorder in Minnesota link

We could not assess changes in actual disease incidence with these data, but federal and state administrative changes in policy and law favoring better identification and reporting of autism are likely contributing factors to the prevalence increases and may imply that autism spectrum disorder has been underdiagnosed in the past.

Is autism more common now than ten years ago? link

Even though the prevalence rates refer to slightly different age cohorts, it was concluded that the apparent increase is in part due to better detection, but also to new cases born to immigrant parents. Typical cases of autistic disorder accounted for 75% of cases, and 20% had normal or near-normal IQs.

Reevaluating the incidence of pervasive developmental disorders: impact of elevated rates of detection through implementation of an integrated system of screening in Toyota, Japan. link

An approximately 11-fold increase was noted in prevalence of PDD compared to a previous survey two decades ago, and two main factors were believed to account for this apparent sharp increase. First, inclusion of high-functioning subjects detected during infancy, and second, higher rates of diagnosis resulting from an integrated process of screening.

And the one ‘for’ an increase.

Autism Increase Not a Result of Reclassification link

I’d like to state that an increase is entirely possible, as factors like anti-depressant use in pregnancy and the older age of parents up the risk for autism, so a slight increase is entirely possible. However, the bulk of the papers published agree that it’s the better diagnosis and widening of the definition of ASD that’s caused the massive increase in diagnosed cases of autism. And my personal experience agrees with them.

But most crucially.… Thimerasol containing vaccines were removed from use in California in 2001. Did the incidence of autism fall? Nope. It still rose.

Thimerosal Disappears but Autism Remains

Using an ecologic design and data from the California Department of Developmental Services, the authors showed that the prevalence rate of autism increased continuously during the study period even after the discontinuation of the use of thimerosal in US vaccines in 2001. Had there been any risk association between thimerosal- containing vaccines and autism, the rate of autism should have decreased in young children between 2004 and 2007. Instead, the rate increase did not attenuate, indicating that thimerosal exposure bears no relationship to the risk of autism.

Childhood vaccines have been one of the most important advances of modern medicine in the 20th century. Unfortunately, once vaccine programs have been successful at controlling preventable infectious diseases, people shift their attention to the potential adverse effects of vaccines (which are rare but can nevertheless be serious). Deaths of young children occurred in Europe because of the MMR-autism scare, and as shown in a recent US measles outbreak, 17 children’s health was put at risk by parents who refused to vaccinate their children because of the supposed vaccine autism link. Parents of autistic children should be reassured that autism in their child did not occur through immunizations. Their autistic children, and their siblings, should be normally vaccinated, and as there is no evidence of mercury poisoning in autism, they should avoid ineffective and dangerous “treatments” such as chelation therapy for their children.

 

 

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