Epidemiology of autism: Current controversies and research directions

In many respects, the epidemiology of autism is still in its infancy. Although important questions remain unanswered, epidemiologists are making significant progress in several areas of inquiry that will be addressed in this presentation: How common is autism? Has the prevalence changed over time? What demographic and environmental risk factors have been identified that may provide clues to underlying etiology? What research is being done to search for early biologic markers for autism and related disorders? Epidemiologists like to count “cases” to estimate the frequency with which autism occurs in a population. However, prevalence estimates are heavily influenced by the methodology used for identification of affected individuals, making it difficult to compare prevalence across different time periods or populations. Current estimates of autism prevalence based on different methodologies and factors contributing to observed time trends will be provided for consideration. The tools of epidemiology are also useful for identifying demographic and environmental risk factors that may provide clues to underlying etiology. Preliminary data will be presented from large California studies on characteristics of parents and newborns that are associated with risk of autism. Finally, in collaboration with basic scientists, slow progress is being made in identifying and evaluating early biologic markers for autism. Current studies will be described and preliminary data on newborns presented.