When Leo Kanner was helping to discover autism back in the 1930's and 1940's he noted that at around the toddler age many but not all autistics started showing severe traits. This phenomenon is known as regressive autism. There were not many if any vaccines back then. Now there is and children receive them at the toddler age. Often an autistic toddler receives their vaccinations and severe traits appear right after that so parents are naturally going to think there must be a connection. No peer reviewed study and there has been a bunch of them has proved vaccines causes autism. Yet there are bunch of people known as anti vaxxers that believe vaccines cause autism and the drug companies are paying off the scientists and the media to rig the studies.
Autism historians which there are only a few at this point have pointed out that there were people who showed many autistic traits hundreds of years ago well before there were vaccines.
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Professionally Identified and joined WP August 26, 2013
DSM 5: Autism Spectrum Disorder, DSM IV: Aspergers Moderate Severity
“My autism is not a superpower. It also isn’t some kind of god-forsaken, endless fountain of suffering inflicted on my family. It’s just part of who I am as a person”. - Sara Luterman