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Is There an Autism Epidemic? PDF Print E-mail
Swift
Written by Dr. Steven Novella   

There is no question that the rates of autism diagnosis have been increasing in the US and the Western world. The latest Centers for Disease Control (CDC) estimates indicate that 1 in 88 children have been diagnosed as being on the autism spectrum (1/54 boys and 1/252 girls). This is up from just two years ago when the estimate was 1/100 children, and much higher that the 1990s when estimates were around 1/250.  

It certainly looks like we are in the middle of an autism epidemic, but experts are not so sure, and for good reason.  

As a general rule in any scientific discipline when a measured quantity is changing over time you have to consider the possibility that the method of measurement is changing, rather than the thing being measured itself. In medicine this often relates to the method of diagnosis. To be precise we often say the rate of diagnosis is increasing (or decreasing), rather than the rate of the disease - unless all diagnostic artifacts have been reasonably ruled out.  

Autism is particularly susceptible to diagnostic artifacts. Various factors have been identified that could, and probably are, affecting the rate at which the autism diagnosis is made.  

The first is an expansion in the diagnosis itself. In fact autism is part of what is now called autism spectrum disorder, because we recognize that it exists along a fairly broad spectrum. If you cast a wider net, you're going to catch more fish - that doesn't mean there are more fish.  

Related to this issue is the fact that autism is a clinical diagnosis - it's based on recognizing a set of signs and symptoms. At present there are no biological markers that can be used to reliably diagnose autism. There is therefore no laboratory confirmation or objective result that can be used to compare prevalence over time. Clinical judgment is required, and that judgment can drift over time.  

Awareness and familiarity with autism can therefore also lead to more diagnoses. Teachers may be more likely to consider the diagnosis and raise the issue with parents, and doctors may be more likely to make the diagnosis.  

Yet another related issue is so-called diagnostic substitution. There are several related diagnoses the may be more likely to be diagnosed as autism today. Two or three decades ago, however, the same children might have been diagnosed with a non-specific developmental disorder, or a language disorder.  

Surveillance is another issue - the effort being made by school systems and others to identify children who have special needs because they fit on the autism spectrum.

The scientific evidence strongly supports a major role for all these various factors in explaining the increase in autism diagnosis. Studies have shown that there is diagnostic substitution (as autism diagnosis goes up, other related diagnoses go down), there is increased surveillance, and there is wider recognition of autism. The chance of having a child diagnosed with autism strongly corresponds to living near other families with a child on the spectrum, and being in the same school system. Therefore social contact with others with the diagnosis increases the chance of being diagnosed.  

Several studies have shown that when the same methods are used to compare different cohorts of children born at different times, the autism prevalence is the same. Further, the prevalence of autism in different age groups (when the same surveillance and diagnostic methods are used) appears to be the same. If the true incidence of autism were increasing then younger age groups would have a higher prevalence.  

It is possible, therefore, from these various factors that the apparent rise in autism is entirely an artifact of diagnosis and surveillance. It is difficult to prove this, however, and so there is always a certain amount of uncertainty. It is also possible that there is a real increase in the incidence of autism over time, but there is no data that establishes that there is a real increase beyond the factors described above.  

Of course there are some groups that are invested in the notion that autism is truly increasing and represents an epidemic. Most notable is the anti-vaccine movement, who over the last decade have been blaming the increase in autism on vaccines. Initially they blamed autism on the MMR vaccine, but the scientific data did not support that claim, and the credibility of the originator of this fear, Andrew Wakefield, has since crashed and burned.  

After the MMR hypothesis failed they next turned to mercury in the form of thimerosal in some vaccines. They confused correlation with causation by arguing that autism rates were increasing as the vaccine schedule also increased. By the end of 2002, however, thimerosal was removed from the routine vaccine schedule in the US, and therefore the amount of exposure to thimerosal plummeted. Advocates of the thimerosal hypothesis (such as David Kirby) predicted that autism rates would also plummet.  

They were correct in that, if thimerosal were a significant contributor to autism then the rates should drop considerably once thimerosal was largely removed from childhood vaccines (it was still present in some flu vaccines). Since 2002, however, autism diagnosis rates have continued to increase at the same rate. We are now 10 years later, and there is simply no justification for clinging to the thimerosal hypothesis any further (of course this hasn't stopped antivaccinationists).  

Ironically the antivaxers are now using the continued increase in autism diagnosis to argue that vaccines cause autism, even though that increase contradicts their prior predictions.  

The data clearly shows that much, if not all, of the increase in autism is due to expanded diagnosis and surveillance. It is still possible that there is a real increase, but more research would be needed to establish that.  

However, regardless of cause, we now know that autism is very common. It therefore deserves a proper level of attention and resources, both for research and services for those on the spectrum.

 

Steven Novella, M.D. is the JREF's Senior Fellow and Director of the JREF’s Science-Based Medicine project.

Dr. Novella is an academic clinical neurologist at Yale University School of Medicine. He is the president and co-founder of the New England Skeptical Society and the host and producer of the popular weekly science show, The Skeptics’ Guide to the Universe. He also authors the NeuroLogica Blog.

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A different name
written by EarlyOut, March 31, 2012
Excellent article, one that deserves to be spread far and wide.

I found myself thinking that when I was a kid, there weren't so many autistic kids around. Then I stopped and thought about it some more. There was Richard, that "weird" kid in my second-grade class, who was pulled out of the school by the next year, and shipped off to some special school. And there was Jay, the "weird" kid next door, who never did manage to survive in the mainstream. Looking back, both of them exhibited almost textbook symptoms of autism. It's just that 50 years ago, we didn't call it that. Out of maybe 100 second-graders, one was profoundly autistic. Out of about 50 kids in my immediate neighborhood, one was profoundly autistic.

In short, my own admittedly anecdotal experience would support the idea that the disorder isn't becoming more prevalent - it's the diagnosis that's rising.
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However...
written by GusGus, March 31, 2012

Is it conceivable that there might be some actual increase in autism beyond diagnosis artifacts? I'm thinking environmental effects. Specifically, air and water pollution, and hormones and antibiotics in food. I'm not claiming this - just asking...
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Other causes?
written by EarlyOut, March 31, 2012
@GusGus: Yes, it's conceivable. But first, we need to establish whether or not there really is an increase in autism. There's no point looking for "new" causes if the disorder itself is not becoming more prevalent. Second, why focus on air and water pollution, or hormones and antibiotics? Is there any reason to believe that these are responsible for autism? Is there any research that points to a causal relationship there? Maybe autism is caused by increased UV exposure because of holes in the ozone layer. Maybe it's caused by shifts in the earth's magnetic field. Maybe it's caused by global warming. Maybe it's caused by pregnant women consuming too much peanut butter. Maybe it's caused by increasing political rancor in Congress.

Bad science often occurs when people leap to explanations for things without any justification. I'm reminded of the "leukemia clusters" that were discovered in some neighborhoods a couple of decades ago. First, further research indicated that just by the laws of probability, some things will sometimes "cluster" in a way that makes us suspicious - but it's just random chance. Second, people noticed that there were electrical substations in these neighborhoods, and jumped on the idea that it must be caused by EM radiation. There was no reason to think that, and lots of good reasons to believe that it wasn't possible. But the fear it instilled is still kicking around today (cell phones and brain cancer being the prime example of unwarranted hysteria).
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I agree with EarlyOut, Lowly rated comment [Show]
Bad analogy
written by EarlyOut, March 31, 2012
@Davis: "Man made global warming is to liberals the same as vaccines are to the anti-vaccine crowd."

Bad analogy.

There is no evidence that vaccines cause autism, ample evidence that they don't, and no plausible explanation for a mechanism whereby vaccines could cause autism.

There are boatloads of evidence that human activity is contributing to global warming, and the mechanisms whereby it's happening are fairly well understood (greenhouse gases). If you don't think that large amounts of carbon dioxide in the atmosphere will warm the surface, for example, you might want to take a little trip to Venus to see for yourself. And if you don't think humans are pumping carbon dioxide into the atmosphere, I'd be forced to call that "willful ignorance." There are only a handful of fringe scientists who are willing to ignore the evidence, and claim that it's not happening.

The only one letting his emotions blind him to the evidence in this instance is you.
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Statistical significance
written by overlord624, April 01, 2012
Having been reading Slashdot's comments on the same subject recently, I found an interesting anecdote.
One of the readers have been diagnosed with an Asperger's at the age of 37 in 2010. But do they include him in the 2010 results or the 1973 results?
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Poor Caller X...
written by EarlyOut, April 01, 2012
....always on the wrong side of every debate.

There is no evidence that the Medieval Warm Period was caused by human actions. There is evidence that the current warming period is, however. In fact, recent research indicates that the Medieval Warm Period wasn't even a global phenomenon, but was just a regional occurrence. In short, the Earth wasn't warmer, on average - the heat was just distributed differently.

And just because something is capable of occurring naturally does not mean that it can't also be caused by humans. Your argument is that, because it sometimes rains, it's not possible to get wet because someone is pointing a sprinkler at you, instead.

Venus' proximity to the Sun does not account for its extreme surface temperature. Its atmosphere does. Remember, Mercury is much closer to the Sun than Venus, but Venus is still hotter. Look it up before you make pronouncements.
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Yes, which date?
written by EarlyOut, April 01, 2012
@overload624: "But do they include him in the 2010 results or the 1973 results?"

Indeed! If one believes that autism is a congenital problem, autism cases should be ascribed to their birth years. If one believes that it's caused by exposure to something environmental (in the broadest sense of the word), the cases should probably be ascribed to the year in which the sufferer reached, say, age 5. Relying on the year of diagnosis is probably the worst choice - I'm not aware of any instances of someone "coming down" with autism in adulthood, or even at any time beyond the preschool years.
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Misdiagnosis?
written by ryuthrowsstuff, April 01, 2012
I'd be curious to see how misdiagnosis or over diagnosis factors into this. We've all heard stories from the anti-vaccine people about miraculous cures or improvements thanks to quack treatments, and these often get written off as misdiagnosed children or children who never had a developmental disorder in the first place. So I've long assumed this must be bumping the numbers up a bit.

POINTLESS ANECDOTE:

In the early 90's when my younger brother was around 2 we noticed he was "developmentally delayed". He didn't regularly speak, new very few words, and often mispronounced the ones he knew. He didn't play or interact with the rest of us often, didn't respond to adults when called, and even engaged in that stereotypical rocking behavior. The pediatrician my mother took him to was convinced he was autistic and sent us to a specialist.

15 minutes into his doctors visit my mother was told that he had an easily reversible inner ear problem. He was something like 60% deaf and it probably (and in the end did) account for all of his issues. Including the rocking behavior, apparently it was the result of balance troubles. A quick procedure and a preschool for the hearing impaired later the kid was perfectly fine.

Interestingly though the original doc remained convinced my brother was autistic, even to the point of telling several of my brother's elementary school teachers "hey that kids autistic" and spreading the word among other parents at the school. He didn't admit his mistake until mt brother ran into him at 14 and read him the riot act.
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@earlyout, Lowly rated comment [Show]
...
written by Willy K, April 01, 2012
written by Davis, April 01, 2012
When I was a kid


Apparently you still are, at least intellectually. So sad.... smilies/cry.gif

Yes, that is an observation and an insult. smilies/shocked.gif

It's just like "Two, two, two mints in one!" TM Certs - a product of American Chicle Company. smilies/wink.gif
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Content-free
written by EarlyOut, April 01, 2012
@Davis: Invective is not a persuasive argument. You obviously have no facts at your command. All you can do is regurgitate Fox News talking points.
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The costs of environmentalism
written by EarlyOut, April 01, 2012
We're getting pretty far off-topic at this point, but it's still worth saying...

Almost every economist who has studied the costs of protecting the environment has discovered an interesting little tidbit, one that the wingnuts just can't stomach. When businesses are forced, kicking and screaming, into replacing outdated equipment and processes in the name of environmental protection, they find that it does, indeed, hurt their bottom line in the very short term, which is as far as most businesses look. But in the longer term, they almost all find out that modernizing ends up making them more productive and, therefore, more competitive and more profitable. It cuts down on their need to get rid of toxic by-products, cuts down on the costs of taking care of injured workers, cuts down on the costs of maintaining old, failing equipment, etc., etc. In short, all the gloom and doom talk about how it's going to "jeopardize security and jobs" turns out to be dead wrong.

Facts are sometimes inconvenient things.
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Indeed, the numbers are compelling
written by powerpoint, April 02, 2012
Indeed, the numbers are compelling. In 1990, autism was diagnosed in about 4.7 out of every 10,000 American children. By the end of 2006, that number had risen to approximately 60 out of every 10,000, which translates to 1 out of every 166 American kids.
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Deeper and deeper
written by EarlyOut, April 02, 2012
@Caller X: When you're in a hole, stop digging.

"So you agree it wasn't caused by our snowmobiles and jet-skis." Of course. But to repeat, with the hope that it will sink in eventually, just because warming wasn't caused by human activity in the Middle Ages, that doesn't mean that it's not possible for human activity to be causing warming today. The Earth is getting warmer today, but the factors that are believed to have caused European warming several centuries ago don't appear to be in play now. Something else is causing the warming today, and all signs point to the gases we're pumping into the atmosphere. Which part of this do you find so incomprehensible?

"Because we were all over Indonesia and Australia and Siberia measuring temperatures in those days. Lots and lots of reliable data from all over the world." The thermometer hadn't even been invented in the Middle Ages. So how do you think we know that Europe was warmer then? Certainly no one was measuring the temperature - they didn't have any means of doing so. Do a little reading about climate history - climatologists obviously can't rely on measurements at any time before the 18th Century, and even before the 20th Century, the records are pretty sketchy for most places in the world. Before that, they have to look to other clues, including information from all sorts of sources - distibution of fossils, ice cores, tree rings, and yes, even human reports about what crops they were growing, and when the growing seasons stopped and started.

"Yes, so close to the sun that it can't have an atmosphere." So what? You've missed the point again. Mercury is closer to the Sun than Venus. But Venus is hotter than Mercury. Why? Because Venus' atmosphere, loaded with carbon dioxide, acts like a greenhouse. And if we load our atmosphere with carbon dioxide, that's exactly what it's going to do - act like a greenhouse. The facts aren't in dispute - the carbon dioxide concentration in our atmosphere has spiked over the last century, and our global temperatures are rising. We have the data, and we have a rock-solid explanation for the causal relationship. That part of the debate is over. The only subject open for discussion is what we should do about it. Your answer seems to be, "Let the chips fall where they may." Most of us, however, think that doing a vast, uncontrolled experiment on the only planet we've got is not a very smart thing to do.

Treating this subject as if it were a playground fist-fight, by the way, is not very productive. Name-calling isn't going to rescue our grandchildren.
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@EarlyOut: Back to Autism
written by sibtrag, April 02, 2012
Disclaimer: I am not an expert on autism in any way.

We can look at the various proposed causes for autism using our basic skeptical thinking which has caused us, for example, to reject homeopathy out-of-hand as being implausible given knowledge of basic chemistry.

Mercury in vaccines:
Plausible, but dis-proven. Mercury is generally toxic and in some forms causes CNS problems. Injecting it into people whose brains are rapidly developing could be problematic, so the decision to remove it fits the precautionary principle. Unfortunately, now we know that this wasn't a cause. Oh if it were that simple.

Environmental effects/pollution/etc:
Plausible, but not helpful. It is well established that various pollutants are absorbed into the body from the environment. There are myriads of substances which have not been studied for these effects in all the combinations found in the environment. Any subset of which could provide an environmental trigger in someone genetically predisposed to the disorder. But considerable work would be required to identify the culprit(s). I expect that current work to study the disease would consider various environmental triggers. Question is how far would/should we go with the precautionary principle once a candidate is identified.

UV exposure:
Plausible, but actual UV exposure is decreasing instead of increasing due to concerns about skin cancer. (See vitamin D)

Changing Magnetic fields:
Implausible. The Earth's magnetic field is indeed decreasing and the poles are moving, there is already a 2x variation in intensity across the globe, so this would show up as a strong regional variation in autism long before the slow changes would have any effect.

Global warming:
Implausible. Again, the seasonal and regional variation in climate is much larger than the comparatively gradual overall warming of the planet.

Peanut butter:
Implausible as peanut butter has been around for quite some time and is GRAS. Certainly less plausible than other environmental factors which are much more recent.

Rancor in congress:
Hard for me to judge. The body's stress response is very complex, so someone whose stress is caused by congress could suffer various effects.

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prenatal stress (rancor in Congress)
written by sibtrag, April 02, 2012
I guess I was wrong....rancor in Congress should be upgraded to plausible. At least according to one analysis in pubmed. It surveys the field and identifies various mechanisms.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2632594/

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Rancor in Congress
written by EarlyOut, April 02, 2012
@sibtrag: Perhaps we should be looking at whether autistic children were exposed to hefty doses of CSPAN in infancy. I think that might be enough to cause me to turn inward. smilies/wink.gif
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ironic..., Lowly rated comment [Show]
...
written by Willy K, April 02, 2012
I bet EarlyOut and Willy K are both autistic. That would explain everything.


Davis, comments about betting should be posted in the "Innumeracy, Gambling, and Absorption Walls" article by Dr. Steven Novella.

Thanks you,
Your friendly neighborhood autistic. smilies/tongue.gif
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Such incisive commentary
written by EarlyOut, April 02, 2012
@Davis: So that's all you've got, eh? It really speaks volumes.
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@EarlyOut
written by Davis, April 02, 2012
No, I have much more info. But, like you, I have spoken to enough homeopaths and ghost believers to know you dont change minds usually. You can only present facts.
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And yet....
written by EarlyOut, April 02, 2012
@Davis: And yet, you post only invective, with no factual information at all. In fact, you haven't even made a single rational argument. You haven't managed anything other than a post about global warming that could be summarized as, "It's all made up." Telling.
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@earlyout
written by Davis, April 02, 2012
Never said "its all made up". Just saying its very possible and probably likely, that the data supporting man made global warming is suspect at best. Think about it, difficult but try, if any anti-vaccine expert were caught massaging the data and sending emails to coerce other experts to change the data to meet an objective, would that not make their entire argument questionable? Liberals have the Pavlov response every time a subject near and dear to their hearts is "supported" by science. I am just saying its possible you are being duped.
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...
written by Willy K, April 02, 2012
@ EarlyOut

Davis calls us "autistic." Does he mean we're liberal or conservative autistics?
I guess I'd prefer to be autistic than being a Davis.
I think he might be duping us into believing he a rational Human Being. smilies/cheesy.gif
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Please
written by EarlyOut, April 02, 2012
@Davis: Oh, lord, you're actually going to vomit up the great "global warming email scandal" as your justification for being unwilling to believe the mountain of evidence out there? The email "scandal" that's been pretty thoroughly debunked? The emails taken out of context, and with phrases wilfully misinterpreted by the "deniers?" Really??

Your credibility has just plummeted to something asymptotically approaching zero. You're grasping at a straw that isn't even there, for f*ck's sake!
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...
written by Caller X, April 02, 2012
The thermometer hadn't even been invented in the Middle Ages. So how do you think we know that Europe was warmer then? Certainly no one was measuring the temperature - they didn't have any means of doing so.


Because there were sheep ranchers living in Greenland?

Because there were grape growers in Nova Scotia?

Because of the lack of contemporaneous accounts of the Thames freezing over?

Nanny nanny boo boo.

.
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I give up
written by EarlyOut, April 02, 2012
The combined brilliance of Caller X and Davis is clearly overwhelming. Oy. One of them is unable to follow the simplest of reasoning (I'll leave it to others to guess which one), and the other is willing to swallow one factoid (in the true sense of the word - something that resembles a fact, but isn't), and let it cast doubt on objective reality. Ultimately, it's depressing. Every time I encounter this level of aggressive stupidity, it makes me wonder how the species can possibly survive.

I'm intrigued by one thing, however. If you're evidence-proof, and incapable of fairly basic logical reasoning ability, how do you decide what's true, and what isn't? Doesn't that set you up to believe just about any nonsense that comes down the pike?
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...
written by Willy K, April 02, 2012
I give up
written by EarlyOut, April 02, 2012

NO! Don't give up!
Davis, Popsaw and Caller X have been sent here to test our skeptical strength.
They are not actual people, there are examples of Poe Law's.
People who are that crazy and hostile would not stay around here for so long.
They purposely try to hijack every thread and send it off bizarre tangents.


The article by Dr. Steve was about autism. I saw a bit on ABC network news the other day about autism and someone said that they have found via MRI scans some difference in the brains of some autistic people. It is mentioned on the WebMD website, I wonder if Dr. Novella has any thoughts on that?
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...
written by Marcus.O, April 03, 2012
I believe that anytime there is a broadening of what a certain "disorder" is that there will be more instances. The statement that if you cast a wider net you will catch more fish not that there are actually more fish is so true here and in any disorder. It seems that there are a lot of people who want to place a label on anything that might be out of the ordinary, especially if it helps them to further their agenda.

 

There is no real epidemic of autism, just a tilt over meaning of what the disorder but that does not stop those who are against vaccinations from claiming that it's an epidemic.



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Or maybe...
written by EarlyOut, April 03, 2012
Or maybe they're just prime examples of the Dunning-Kruger Effect. Tough to tell, isn't it?! smilies/grin.gif
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...
written by Willy K, April 03, 2012
Or as Forrest Gump's mama would say "Stupid is as stupid does." smilies/wink.gif
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FOX does it again
written by ayhtida, April 04, 2012
And this is the stuff that our fellow citizens watch on TV. Skip to the 5minute mark to see the lady on the left talk about how a causal relationship has been established (in court, none the less), and how vaccine manufacturers knowingly continue use of 'toxins' and cannot be sued.

http://video.foxbusiness.com/v/1546174739001/how-are-vaccines-linked-to-autism/?playlist_id=933116663001

But then again, if you watch Fox, you don't have any standards anyway.
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...
written by Halk, April 10, 2012
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior.I am sorry to hear about these sick people,it's hard to imagine what do you feel if you see your child sick.Autism isn't a typical disease, it has different manifistations.An autistic culture has developed, with some individuals seeking a cure and others believing autism should be accepted as a difference and not treated as a disorder.Hopefully, we will get a success in fighting this disease, because it's awful to hear how many people are sick.
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