Are we really this rare?

Post Reply New Topic

According to the CDC (Center for Disease Control) in the US, 1 in every 42 boys born have some form of Autism. 1 out of every 189 girls. I have seen studies that speculate that the rate in girls is higher than this and that girls are underdiagnosed because of less pronounced social issues. Tony Attwood speculates that is a man has ASD 25% of their children are likely to as well. If a woman has ASD 50% of her offspring are likely to as well. There is no clinical evidence to support this however.

AS itself is pretty rare. Under 1 percent by a bit.

AD was a little under 1 percent.

PDD-NOS was around 1 percent.

So, you get around 1.5-2 percent overall (which is around the current figure).

Which is rare. Not extremely rare. But rare nonetheless.

Current figure is 1 in 68. Whether you believe that Autism is under or over diagnosed will decide if you think it is rare (the amount of people that believe the amount of diagnosis is correct seems minuscule)

For the US, the CDC figures are here: http://www.cdc.gov/media/releases/2014/ ... order.html

That's 1 in 68 overall, 1 in 42 boys, 1 in 189 girls with considerable variation between states.

TLDR: if you think autism should be less common, you are probably influenced by factors other than data/factual evidence. Given the prevalence of autism and the role of common variations in autism, it is to be expected that there would be tremendous variation in many characteristics in individuals with autism.

Slightly expanded thoughts:
If autism was caused by a handful of SNPs you might have autistic people being clones with a limited range of features, but given the very polygenic nature of autism and the importance of gene-environment interaction, you would expect a heterogenous autistic population.

You would also expect representation from all points along the curve for general intelligence and some autistic representation among people of great ability in many areas. It would be irrational to suppose that people of great accomplishment cannot be autistic, as has been suggested in the debates on posthumous diagnosis of famous people. There are all sorts of procedural problems with such diagnoses, but "people of such accomplishment cant be autistic because most autistic people don't have such abilities" is not one of them.

More detailed thoughts:
Recent studies show that genetic variations account for slightly more than half of the chance that a child will be autistic. Environment is just slightly less important, but still hugely important.
http://sfari.org/news-and-opinion/news/ ... utism-risk
http://www.medicalnewstoday.com/articles/279902.php

Given what is known from behavioral genetics and the study of other conditions with similar complex causes such as schizophrenia and even relative simple inherited characteristics like height, this information has quite a few implications.

Consider:
The "four laws of behavioral genetics" (first three from Eric Turkheimer, University of Virginia and the fourth from James Lee at the University of Minnesota) are

1. All human behavioral traits are heritable
2. The shared family environment has minimal impact on individual differences in behavior
3. The non-shared environment exerts a major influence on individual differences in behavior (i.e., biographical events unique to the individual)
4. Human behavioral traits are polygenic (There is no single gene for most behavioral or physical traits)

Given this understanding, it is to be expected that conditions with a behavioral component will typically be polygenic (as studies show ASDs are) and have a strong non-shared environmental influence (as ASDs do). We can further conclude that gene environment (GxE) interaction is likely to be very important (as studies suggest in ASDs).

There are now many studies that show features of autism in the non-autistic siblings of autistic people. This observed evidence strongly supports the idea of a broader autistic phenotype, with subclinical traits occurring at even higher rates among the relatives of the diagnosed. ( http://sfari.org/news-and-opinion/news/ ... first-year , http://sfari.org/news-and-opinion/in-br ... n-families )

So we have a picture of autism that should lead us to expect (or at least not to be surprised by) relatively high incidence and a very heterogenous population. It seems likely to me, given that we know the genetic changes in individuals with autism can have synergistic effects in the proteins they encode ( http://sfari.org/news-and-opinion/news/ ... teractions ) that we will find clusters of phenotypes within ASD. Some of the "those supposedly autistic people are not quite like me or these autistic people I know, therefore they do not really have autism" arguments that we see from time to time on WP are probably the result of this clustering. I strongly suspect that this will also account for an "Asperger's" cluster within the normal to high IQ (aka HFA) ASD population. But that's speculation. Evidence will be coming in though, so these issues won't be matters for speculation for ever.

Last edited by Adamantium on 22 Jul 2014, 9:23 am, edited 1 time in total.

There is no actual strict demarcation as to when autism "begins" and "ends." It's highly subjective, even amongst clinicians.

There is a bias toward NOT diagnosing autism, especially when "classic" symptoms (e.g., stimming, spinning toys, exquisite social withdrawal) are not apparent.

With DSM V, it seems as if the increase in "incidence" will slow somewhat, since people previously diagnosed with Asperger's might now be diagnosed with "sensory processing disorder."

Frankly, the change, in about 2 to 3 years--from 1 in 115, to 1 in 88, to 1 in 68--is pretty dramatic

Not even close.

The statistics for PDD in general tend to stick around 1 in 100, and there's 7 billion people on earth.

Let's do the math.

That would mean that 70 million people have PDD, a considerable number.

The DSM criteria and the goals of clinicians will in the end be less important than the data being generated by researchers. There will certainly be some interplay between them but the data will not be denied in the end. New understandings will emerge from analysis of that data that will eclipse the current battles over diagnostic criteria. This seems inevitable, barring catastrophic failure of the global civilization. It's like watching alchemy become chemistry. The confused understanding of the past is giving way to a more precise and accurate understanding based more in observation and less in conjecture.

If there is not a strict demarcation between "autism" and "non-autism", who could you say that there is a bias toward not diagnosing autism, instead of a bias toward diagnosing autism?

For various reasons:

1. Clinicians are reluctant to pin a label on a person.

2. Clinicians believe autism is over-diagnosed.

3. Clinicians believe autism has an over-broad definition

Amongst others I can't think of right now.

I just saw a blurb on the news that said in the pacific northwest, autism dx's are more common than in the rest of the nation. I wonder why that is.

1.6% (right now) are autistic. I would say this only applies to Western countries, as other social structures have different ideas of autistic people.

Similar statistics:
1.5% of the world with red hair
1.65% of the US gay or lesbian
1.7% of the US is muslim

Comparison statistics:
14.1% of the US is black (including black mixed with other races)
50.8% of the US is female (not an actual minority, but a social minority)
0.38% of the US is deaf

Most people know about 300 people well enough to come up with their names and basic contact information. For example, you knew Larry in grade school and he lived in XYZ city at that time. You know Sylvia from the grocery store who rings up your orders.

This means that most of us know around 4 people who are autistic, who have red hair, who is a gay man or lesbian woman, and who is muslim. You may not know it, because you may not know the person well enough to have personal information about it. You probably don't know a deaf person, you definitely know a woman, and you should know about 20 black people.

Tony Attwood has suggested, that there may be as many as 2% on the spectrum, all in all - 1 for each 50.

I know one black person, 6 aspies, 3 gay folk, a handful of females including my sister.

Makes sense why I love the "grunge" movement so much from the 90's.

are grungers are on the spectrum?