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tazzygirl -> RE: Vaccines (10/27/2010 3:42:24 PM)
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Perhaps this might help some realize that with the broadening of a category of mental health, there will be an increase in the number of those who fit that category.
That the number of new autism diagnoses is dramatically increasing is generally accepted and not a point of debate. The historical rate of autism is about 4 per 10,000 and the more recent estimates are in the range of 15-20 per 10,000 (30-60 per 10,000 for all pervasive developmental disorders of which autism is one type). (Rutter 2005) The controversy is about what is causing this rise in diagnoses. There are two basic hypotheses: 1) That the true incidence of autism is rising due to an environmental cause, 2) That the rise in incidence is mostly or completely an artifact of increased surveillance and broadening of the definition of autism. These two hypotheses make specific predictions, and there is much evidence to bring to bear on their predictions – this recent study only being the latest.
The confusion about the epidemiology of autism is one common to scientific medicine. Whenever historical comparisons are made it is possible that changing definitions and practices over time will distort those comparisons. This is why medical scientists are often reluctant to change nomenclature (disease names) and definitions – doing so immediately renders the literature obsolete. All subsequent literature must now have a footnote. But the progress of our understanding of biology and disease makes such changes unavoidable.
In the 1990′s the diagnosis of autism was changed to autism spectrum disorder (ASD) – the new name reflecting the changing concept of autism to include a broader spectrum of symptoms, including much more subtle manifestations. In particular a diagnostic entity known as Aspergers syndrome, which is essentially a subtle manifestation of autism features, was classified as part of ASD. Any time you broaden a category the number of individuals that fit into that category is likely to increase.
Autism researcher Eric Fombonne found that:
Recent epidemiological surveys of autistic disorder and other PDDs have heightened awareness of and concern about the prevalence of these disorders; however, differences in survey methodology, particularly changes in case definition and case identification over time, have made comparisons between surveys difficult to perform and interpret. (Fombonne 2005)
In addition to the broadening of the diagnosis, the social and medical network supporting ASD dramatically increased. There has been increased efforts at surveillance – scouring the community for hidden cases of autism. Further, parents have become much more accepting of the diagnosis, which may partly be due to the fact that is some states the label with facilitate access to special services. And clinicians have become more knowledgeable of ASD so are better able to make the diagnosis, even in subtle cases.
Rutter, in order to test this latter hypothesis that increased diagnostic rates were due largely to changes in diagnosis and surveillance, reviewed literature that contained sufficient information to assess true historical rates of autism. He found that applying modern criteria to these historical records yields similar rates of diagnoses: 30-60 per 10,000. Taylor did a similar review and found the following:
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. (Taylor 2006)
http://www.sciencebasedmedicine.org/?p=95
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