Epidemiologists, sociologists, , medical anthropologists, psychologists, psychiatrists, and all manner of other experts have long been aware of the extent to which statistics about incidence and prevalence of disorders are very much a function of how those disorders are defined.
A change in definition can drastically affect statistics and give the public — unaware of what might have been either a change in wording or the combining of two categories into one — the sense that a disorder is becoming either more or less of a problem.
This has always been an issue in autism statistics, and I wanted to call to your attention to the latest debate over how autism will be defined in the next version of the Diagnostic and Statistical Manual of Mental Disorders.
