Autism spectrum disorders--are they really epidemic?

The aim of this paper is to report on how different external methodological factors influence estimates of ASD prevalence.PubMed searches was conducted using the search terms, "Autism", "Autistic Disorder", "Autism Spectrum Disorders", "Asperger", "Prevalence" and "epidemiology", in combination. In total 49 studies were included. We also performed a manual search for and reviewed related articles referenced in the original articles.The reported prevalence rates of ASD vary widely, and so do the methodology used in the studies.There are reasons to argue that the methods used in some studies cause the high prevalence rates reported recently.