Final answer:
Our current understanding of the causes of autism spectrum disorders is largely unknown, but it is believed to involve genetic factors and incorrect wiring in the brain. The claim that vaccines cause autism has been thoroughly debunked.
Step-by-step explanation:
Our current understanding of what 'causes' autism spectrum disorders (ASD) is that it is largely unknown, apart from some well-characterized genetic forms. Variants of several genes have been found to correlate with the presence of ASD, but different mutations in different genes may be required for the disease to develop in each individual. At a general level, ASD is thought to be a disease of 'incorrect' wiring in the brain, with some ASD patients lacking the same level of synaptic pruning that occurs in non-affected people. In the 1990s, a research paper falsely linked autism to a common childhood vaccine. This paper was later retracted, and subsequent studies have shown no connection between vaccines and autism.