Final answer:
Autism spectrum disorders are thought to be caused by a combination of genetic mutations and environmental factors, with some cases linked to specific genetic conditions like Fragile X and Rett's Syndrome. The broader causes involve numerous gene variants and atypical neural connectivity, and the myth linking vaccines to autism has been discredited.
Step-by-step explanation:
The current scientific view is that autism spectrum disorders (ASD) are caused by complex interactions between genetic and environmental factors. While some forms of ASD, such as Fragile X and Rett's Syndrome, are directly linked to genetic mutations, the broader causes of ASD are not completely understood. Several gene variants have been associated with ASD, suggesting a multifactorial etiology—that is, many different mutations in various genes may be necessary for ASD to develop in an individual.
Furthermore, it is thought that ASD may involve atypical neural connectivity or 'incorrect' wiring in the brain, where there is less synaptic pruning compared to typically developing individuals. A controversial study in the 1990s falsely suggested a link between vaccines and autism, but this has been thoroughly debunked through numerous follow-up studies.