Rl called.
(I originally started that sentence with sorry but then decided that I wasn't.
I'm not quite sure what magic diagnostic powers I claimed/implied to have.
But I think you're asking why I think the evidence, in-perfect that it is, does not indicate that MMR (or indeed any vaccination) is linked with an increased risk of ASD.
And that's a question that would require, as I'm sure you are aware, a really long post.
But you bring up one point in particular so lets stick with that.
The idea that a minority of parents with ASD believe that the MMR vaccination caused their child's autism.
And why I think they're could be mistaken.
Firstly, people can be wrong.
This is not new and isn't going to go away anytime soon.
Lots of people thinking the same thing is no defense against being wrong, especially if those people don't make their decisions in isolation.
And , unfortunately, being wrong feels just the same as being right.
So why might this event (the diagnosis of a child with ASD) lend itself to an error of attribution.
Firstly, it's serious.
Having a child with ASD is life altering, incredibly stressful and out of our control.
These are tailor made conditions for humankind's natural pattern recognition abilities to go in over-drive, spewing out false positives.
There are numerous forms of cognitive bias & logical fallacies at play here (the most famous, post hoc ergo procter hoc, has already been mentioned) but there are really are too many list here.
Secondly, there is no cure and proven therapies/access to proven therapies are a long way from good.
This, apart from driving up the stress levels, tends to open people up to information from less conventional sources.
These less conventional sources can offer simple easy answers which gain purchase in the minds of people in these situations because they restore an illusion of control.
At this point I'm going to sort the washing.
I'll be back later.