Years back (2007 to be exact) an autistic blogger wrote a piece “Moving Toward a New Consensus Prevalence of 1% or Higher“. In the late 1990′s, studies had come out showing a prevalence of about 1% in Sweden and, at the time Joseph wrote his piece, more studies had come out, this time in the UK, showing a prevalence of about 1% or higher. Since then we’ve seen multiple reports from the U.S. of 1% or higher, including a recent study claiming 2%. Also, a study in Korea claimed 2.6%, using a whole-population screen. Japan reports 1.8%. Back in the U.S., Puerto Rico is reporting 1.6%.
With all this, it comes as no surprise that a recent study out of Iceland would report a prevalence greater than 1%. In Prevalence of autism spectrum disorders in an Icelandic birth cohort, the authors report a prevalence of 1.2% of clinically confirmed autism. The data, discussed below, shows a clear indication that better identification has played a major role in this prevalence.
For ASD, many had intellectual disability, but the majority did not (click to enlarge). For childhood autism (autistic disorder) the opposite is true. The majority (72%) had ID.