Date Approved


Embargo Period


Document Type


Degree Name

M.A. School Psychology




College of Science & Mathematics


Dihoff, Roberta


Autism, DSM, Prevalence


Autism; Mental illness--Classification--Handbooks, manuals, etc.


School Psychology


The purpose of this study was to determine if the changes that have been made to the Diagnostic Statistical Manuals over the years have had a major effect on Autism and its prevalence rate. This thesis used publicly available data from the Centers for Disease Control and Prevention and Autism Speaks Organization. Since publicly available data was used for this research no demographic or identifiable information about the population was obtained for this study. There are five editions of the Diagnostic Statistical Manual of Mental Disorders and two revised editions. This study specifically looked at the last three editions of the manual. The DSM-III, DSM-IV-TR, and DSM-5 were compared to one another distinguishing the differences and similarities of the changes that have been made between them. The prevalence rates were looked at from the time frame of the year an edition was published to the publishing year of the newer edition. Comparing the number of individuals diagnosed over the years to the changes made in the Diagnostic Statistical Manual and acknowledging any drastic increases. It was found that the DSM criteria changes have not had a major effect on the prevalence rate but due to other factors the rate has steadily gone up over the past couple decades. This study will help the public and people become more knowledgeable about these changes and how they have effected or impacted the disorder over time.