A study looking at autism prevalence in Sweden over a ten-year period has concluded that although clinical diagnoses have risen, cases have in fact remained stable. It puts the increase down to "administrative changes" that have impacted how those on the spectrum are diagnosed and registered. "From the 1970s and onwards the reported prevalence of autism spectrum disorder has increased substantially," write the study authors. "The condition was considered rare, affecting fewer than 0.05 percent of the population, but it is now generally agreed that the lifetime prevalence is at least 1 percent in both young people and adults." In some parts of the world, that figure is even higher. The authors continue: "Despite the increase in reported prevalence of autism spectrum disorder, there is no direct evidence that this corresponds to an increase in the prevalence of the autism phenotype -- that is, the symptoms on which the diagnostic criteria are based."
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