Prevalence statistics for autism spectrum disorders (ASD) vary widely across geographical boundaries. Some variation can be explained by diagnostic methods, case ascertainment and age at diagnosis. This study compared prevalence statistics for two distinct geographical regions, Denmark and Western Australia, both of which have had population-based…

The etiology of autism spectrum disorders is unknown but there are claims of increasing prevalence in many countries. Despite more than a decade of epidemiological investigation, it is still unclear whether the rising trend in prevalence reflects a true increase or changes in diagnostic trends and improvements in case ascertainment. This paper…