It is proven that vaccinations doesn't cause autism.

But I read from various internet/documentary/newspaper sources which claim that they have personally witnessed their child showing signs of whatever the modern definition of autism is within days of vaccination. In short, their child has changed dramatically for the worse. There's even been a user on this website having the same kind of story.

When these stories arise, I read that such a thing is not possible. However, I've never seen a single article coming to the bottom of what did actually cause autism in those cases!

I understand that vaccination didn't cause autism in those cases, but what did cause it?

  • What are you asking? If you're asking "what causes autism", why the vacciantion part? Since vaccinations've been proven to not cause autism, there is no reason to include them in this question.
    – Dariusz
    Dec 9, 2014 at 13:27
  • For the perceived connection, keep in mind that parents may be watching their children more closely after vaccination (especially if primed on vaccination/autism links), or the kid DOES feel a bit ill after vaccinations (which can happen), so symptoms show more strongly. This does not explain what caused the autism, but it COULD explain the "I vaccinated my child and not it is autistic" stories.
    – Layna
    Dec 9, 2014 at 14:02
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    This question appears to be off-topic because it is about physiology, not parenting.
    – Acire
    Dec 9, 2014 at 17:27
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    I agree this is off topic, but when I asked our pediatrician the question of where the anecdotes comes from, her answer was that in many cases, signs of autism becomes very clear around age 2, same age as MMR shot is given. Some signs show up earlier or later, of course, but I find this a reasonable explanation, especially since most stories are like: My aunts best friend's daughter's child got diagnosed with autism after he got vaccinated! and the actual, precise timeline is hazy.
    – Ida
    Dec 9, 2014 at 19:40
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    It seems on topic to me also, if it is a research request. I think if it's a general discussion, then it's off topic as too broad and/or medical specific; questions like this are okay as research requests only, in my opinion.
    – Joe
    Dec 9, 2014 at 21:39

2 Answers 2


Correlation, not causation, is the problem here.

Nothing "causes" autism, it is a natural state for people. It's not even an "illness", it's a combination of personality and behavioral states that we classify as a condition simply because it is outside of "social norms". In short: "it just happens"

The parents have heard that vaccination causes Autism, so immediately after the vaccination they start to look for it and notice some behaviours.

This completely misses the point that those behaviours were already there, unnoticed. That child was always going to show these behaviours, the parent just didn't notice them until prompted. The fact that the vaccines are usually given at around the age a child starts to develop their own individual personality traits only serves to exacerbate this: it's easy to notice newly developing traits. Again, they would have developed anyway, they just happen to be at around the same time.

Note also that Autism is a spectrum not a cross this line diagnosis. Everyone is on the spectrum, it's just that below a certain (rough) point, we stop declaring it as "Autism" and start classifying people as having personality traits. A calm, nerdy, introverted person with low social skills and excellent memory function, for example, is further "up" the scale and more likely to be considered as autistic (or, more likely, having Asbergers) than an outgoing, sociable person with little ability to concentrate (who may be tagged with "ADHD" instead)

Some of these things are personality traits, some are a result of "how autistic" they are, others are both. In essence, though, they are attempt to categories people by their behavior and personality: they do not correspond to a disease or illness.

If you look hard enough you can notice autistic-like behaviour in anybody. I have little ability to emphathise and fairly "tame" emotional response, for example: that doesn't make me Autistic, but it perhaps suggests I'm further "up" the spectrum than somebody more emotionally involved: but I am, for the most part, a well adjusted individual, socially and behaviourally.

In short, they're looking for those behaviours and associating them with the vaccine. The behaviours existed before, and are just part of human existence.

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    While I agree with this answer, I think it is not appropriate for this question: what is appropriate is an answer with sources and details
    – Joe
    Dec 9, 2014 at 15:18
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    I think this is a good answer to the age/vaccine correlation, but it could improved with sources about autism, and autism spectrum.
    – Ida
    Dec 9, 2014 at 19:42
  • Feel free to improve it with sources, guys - I'm not precious about the answer, edit all you like
    – Jon Story
    Dec 9, 2014 at 20:06
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    There may be many things we don't know about, but to my knowledge, nothing just happens. That's not really a good answer to a why-type question. I agree that hypervigilance following vaccines is one reason for the equation of autism with vaccines. Dec 9, 2014 at 21:18
  • @JonStory Similarly to AE, i'll answer the same: this isn't something we should be updating with sources; it's up to you to do that or not. I'm being a stickler here because I think the question is off topic unless it's asking for reputable research - as such, if your answer as given is an acceptable answer, the question shouldn't be allowed (despite it being something I wholly agree with).
    – Joe
    Dec 9, 2014 at 21:41

Causes of autism spectrum disorder

The exact causes of autism spectrum disorder (ASD) are unknown, although it is thought that several complex genetic and environmental factors are involved.

The causes of ASD can be described in two ways:

  • Primary ASD (also known as idiopathic ASD) – where no underlying factors can be identified to explain why ASD has developed.
  • Secondary ASD – where an underlying medical condition or environmental factor thought to increase the risk of ASD is identified.

About 90% of cases of ASD are primary, and about 10% are secondary.

Risk factors

Factors thought to increase the risk of developing ASD, known as ‘risk factors’, can usually be divided into five main categories:

  • Genetic factors – certain genetic mutations may make a child more likely to develop ASD.
  • Environmental factors – during pregnancy, a child may be exposed to certain environmental factors that could increase the risk of developing ASD.
  • Psychological factors – people with ASD may think in certain ways that contribute towards their symptoms.
  • Neurological factors – specific problems with the development of the brain and nervous system could contribute to the symptoms of ASD.
  • Other health conditions – certain health conditions associated with higher rates of ASD.

Autism spectrum disorder - Causes
NHS Choices. Page last reviewed: 18/12/2013.

See the source for a detailed description of all five risk factors.

The causes of autism are still being investigated. Many experts believe that the pattern of behaviour from which autism is diagnosed may not result from a single cause. There is strong evidence to suggest that autism can be caused by a variety of physical factors, all of which affect brain development - it is not due to emotional deprivation or the way a person has been brought up.

There is evidence to suggest that genetic factors are responsible for some forms of autism. Scientists have been attempting to identify which genes might be implicated in autism for some years.

Autism is likely to have multiple genes responsible rather than a single gene. The difficulty of establishing gene involvement is compounded by the interaction of genes and by their interaction with environmental factors. For these reasons genetic testing to diagnose a pre-disposition to an autistic spectrum disorder is not, at present, possible.

Position statement: causes of autism
National Autistic Society, 17 October 2011

There is no known single cause for autism spectrum disorder, but it is generally accepted that it is caused by abnormalities in brain structure or function. Brain scans show differences in the shape and structure of the brain in children with autism compared to in neurotypical children. Researchers are investigating a number of theories, including the links among heredity, genetics and medical problems.

In many families, there appears to be a pattern of autism or related disabilities, further supporting the theory that the disorder has a genetic basis. While no one gene has been identified as causing autism, researchers are searching for irregular segments of genetic code that children with autism may have inherited. It also appears that some children are born with a susceptibility to autism, but researchers have not yet identified a single “trigger” that causes autism to develop.

Other researchers are investigating the possibility that under certain conditions, a cluster of unstable genes may interfere with brain development, resulting in autism. Still other researchers are investigating problems during pregnancy or delivery as well as environmental factors such as viral infections, metabolic imbalances and exposure to chemicals.

About Autism > Causes
Autism Society

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    AE, this actually goes too far on the source side. Your answer should not be solely copy paste sources, but should include both sources and discussion - preferably interweaving sources with that discussion as they naturally flow. But great job collecting sources on the matter.
    – Joe
    Dec 9, 2014 at 15:19
  • @Joe, feel free to edit it to add discussion! :) I can't think of much to add that wouldn't just be me repeating what the sources say - which seems a bit pointless.
    – A E
    Dec 9, 2014 at 15:22
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    AE, that's not really how it works; while I might do that with a question, with an answer it's not generally appropriate for someone else to add significant content to an answer. See the FAQ for what a good answer is, but in particular you should add context to the links and quotes: think of an encyclopedia. They link to the various sources, but they also add a descriptive paragraph to tie it all together. This answer would be a great answer with a paragraph or two tying this information together.
    – Joe
    Dec 9, 2014 at 15:25
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    I'll see if I can think of something to say. ;)
    – A E
    Dec 9, 2014 at 15:43

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