Epidemiological studies have shown that the prevalence of autism spectrum disorders (ASD) has risen sharply in the western world [1,2]. ASD is now thought to occur in approximately one in 100 people  having risen from an estimated 1 in 10,000 people in the 1960s . This trend is illustrated in Figure 1. These data were taken from various US and European prevalence studies, each utilizing differing methods of case ascertainment. Despite methodological differences, this figure serves to broadly illustrate the exponential rise in ASD prevalence.