Fallacy of a "changepoint" in the autism increase

This is my comment on the 2010 paper by Michael E McDonald and John P Paul. "Timing of increased autistic disorder cumulative incidence" Environ. Sci. Technol. 44, 2112-2118.

The authors reckon that they can usefully analyse the autism increase curve by making an approximation of it in terms of two straight lines. They then point out that the junction of the two lines, the "changepoint", at which they suggest the autism increase began, is about 1988-9.

In reality, just about any curve of roughly exponential increase form can have a couple of straight lines imposed on it such as to passably plausibly account for the entire data set. Especially if you set the time axis long enough so the increase will look like an abrupt event rather than a gradual one.

Nice correlations can be found for each line with its corresponding part of the data, and impressively high significance levels pointed out. It does not however follow that the increase is usefully understood in terms of such pairs of lines.

The paper of McDonald and Paul features remarkably small graphs of the increase, which tend to give the impression that there was no increase before their "changepoint". And they use a whopping 50-year timespan. It would be better to have larger (taller) graphs around the critical period so we can examine the end of the "level" section more closely.

I will put here this superb graph of the US IDEA data that others have kindly prepared. (Right-click it to open an enlargement in a separate window.)
(Graph provided by Thoughtful House Center for Children,
Graphing IDEA Professional 2010, Thoughtful House, Austin, TX,
Accessed at http://www.thoughtfulhouse.org/disabilities/ on November 19, 2010.)

It should be quite obvious from this graph that there was not some abrupt changepoint around 1988, and not around any other year either.

One can also see that the increase was already beginning by 1980. This is nicely in line with the update review of the antiinnatia theory in which I state that the cause of the increase was the introduction of non-gamma-2 dental amalgams in the 1970s. (Among other evidence, the world's most famous dentist, Hal Huggins, said they became the new "state of the art" in 1975-6.)

Furthermore there is a conspicuous de-steepening of the gradient at 1992-3. I expect that this was due to some minor improvement of the amalgam usage protocol, such as avoiding for pregnant women, a slightly less toxic formulation, or improved suction systems.

I would not have commented on this "changepoint" paper except that it has been cited by Andrew Wakefield and some Age of Autism people as supposedly showing that the start of increase coincided with some changes in vaccination usage. No it didn't.

Autism did not begin only in the 1930s

In two weeks time there will be published a new book:
The Age of Autism: Mercury, Medicine, and a Man-made Epidemic
By Dan Olmsted, Mark Blaxill

I've not read it (yet) but I can anticipate that I would agree with the authors that autism has increased and involved mercury but would be unpersuaded by their reckoning that vaccinations have been a major factor in the increase.

Here I shall just comment on this first sentence of a preview extract circulated by Safeminds:

"We believe that autism was newly discovered in the 1930s for the simple reason that it was new."

But this first sentence can be shown to be mistaken. Dr Down of Down Syndrome fame had already in the 19th century given good descriptions of both infantile autism and regressive autism.
Reference: Down, J.L. Mental Affections of Childhood and Youth, 1887 originally, re-issued as Classics in Developmental Medicine, No. 5, 1990 Mac Keith Press, London

It was discussed in the 2006 Awares conference. This is a link to the paper by Darrold Treffert.

I also suggest that the concept of the "holy fool" such as portrayed in the play and opera Boris Godunov corresponds with mild autism: a person who speaks the truth that others cannot. And bear in mind that the rare autistic individuals would be likely to have had a hard time surviving in earlier ages; even mildly autisticky people might have had a hard time sufficient to prevent them producing children.

Furthermore, there is the important consideration that a rare condition such as autism pre-1970 would only come to the attention of a person once there is a sufficient level of cosmopolitanism, due to urbanisation and transport, enabling one person to "survey" a sufficiently large sample of people. Down made his observation in 19th century England after the railways were established in the world's first modernised country. Thereafter, the US and Austria started to catch up industrially and so autism came to attention there too. That's not to say that the personal links to mercury stated in the AoA book cannot be also part of the story.

Flawed study of adult autism in UK

The NHS has recently published a study of the extent of adult autism in the UK ("Autism Spectrum Disorders in adults living in households throughout England - Report from the Adult Psychiatric Morbidity Survey 2007").

It supposedly shows that there has not been any real increase of autism over recent decades. This is the same NHS that's just made a huge scare-campaign in support of the swine-flu scam, and that gives its endorsement to the fraudulent SCENIHR report as supposedly proving the safety of dental amalgams, even despite numerous people pointing out the falsities of that report.

This autism report is also unacceptably flawed. Some of the flaws are detailed at this campaigning website (at which some of the other content is itself flawed wishful-thinking):
http://childhealthsafety.wordpress.com/2010/02/10/uksurveyautismlink/.

I myself had dismissed the NHS report for the simpler reason that there is no way indicated of establishing comparability of a test applied to children and a test (even if the same one) applied to adults. Update: You can see in the later published Arch Gen Psychiat version that the diagnostic procedure was a very subjective one (dependent on extended group "training"), rather than a mechanically objective box-ticking or bean-counting exercise. This is reflected in how they went to considerable lengths to assure the reliability of the diagnostic procedure. And yet they did nothing to ensure the (infinitely more important) validity of comparability with others' finding at different ages and different decades. And that's because with a non-longitudinal study it is impossible to establish that. It follows that the survey is evidence of nothing, but only leaves the question open of that comparability.

Oh, and they found that none of the adult "autistics" had previously been identified. Which would not be surprising to those who can have a pretty firm guess that they weren't really pathological cases anyway, in shocking contrast to the deluge of cases now constituting a very un-overlookable national emergency in capitalist-corporate-dominated countries.

I welcome the additional critiques raised by childsafetyhealth. Another critical review can be found in issue 34 of The Autism File. It's a shame that taxpayer money only gets wasted on producing and promoting such worthless rubbish as this NHS/ Leicester univ study, when there are plenty more competent people and ideas around.

More evidence on the autism increase

Uta Frith is one of the most notable names in what we might call the autism research 'establishment'. She has recently stated [1] that autism in earlier decades was usually of the classic, severe variety, whereas nowadays most or many cases are of the mild to moderate or high-functioning variety. Putting that in the context of my view that there has been a major global increase due to a certain identified environmental factor, her observation poses the question of why that environmental factor should have produced generally less extreme autism than the preceding "genetic" form did.

And that is a question that is very happily answered by my explanation of the increase. Because the cause I invoke accumulates postnatally, it only impacts at a later age, whereas the classic genetic causation would impact from long before birth. And so one would indeed expect the new causation to commonly be less severe than the earlier variety.
1. Uta Frith, Autism: A very short introduction, OUP 2008

Age of Onset graph

First graph is from the Autism Research Institute (though named "Institute for Child Behavior Research" during most of this graph). Second is my re-working to show the changing ratio of age of onset. How easily is this data compatible with no increase?