A great deal of misinformation has been spread – particularly by our current President and Secretary of Health and Human Services – about the reasons for the rapid rise in diagnosed cases of autism spectrum disorder over the past half-century. We will review the expansion of diagnostic criteria for the neurodevelopmental condition(s) known as autism, and how these diagnostic changes have contributed to the rise. We will also show that the totality of epidemiological studies establish no link between autism and vaccines and at most a weak association (not necessarily causal) with prenatal Tylenol usage. Extensive twin studies have established a dominant role for genetics and a minor role for environmental conditions in contributing to autism. Ongoing brain imaging studies of people on the autism spectrum are revealing atypical connectivity issues that are associated with some autistic behaviors.