Autism, Rising Prevalence of: Epidemiology

The prevalence of autism is the proportion of a defined population that has autism at a specified time. There is a distinction between the measured prevalence and the disorder prevalence, that is, the actual prevalence of the disorder. The measured prevalence might not accurately reflect the disorder prevalence due to changing diagnostic criteria, diagnostic practices, and other noncausal (i.e., nonetiological) factors, and the relationship between the measured and actual prevalence might have changed over time. This entry first discusses some of the potential reasons for this difference and defines epidemiology. It then looks at autism prevalence trends and their relationship to potential causal and noncausal factors.

The measured prevalence of autism has increased greatly since approximately 1980 through at least 2015. There is scientific uncertainty as ...