Swedish study finds severe autism rates steady while milder cases soar

Scientists at Sweden’s University of Gothenburg analyzed national autism data from 2001 to 2020 and discovered that overall autism diagnoses surged by about 800%, yet the count of cases with co-occurring intellectual disability stayed roughly constant at 5.5 per 100,000 births. The proportion of autistic people with an IQ under 70 dropped sharply from 55.8% to 6.7%, reflecting an 1,800% increase in diagnoses of individuals without cognitive impairment.

Co-author psychologist Sebastian Lundström explained that clinicians now assign autism based on fewer symptoms, producing a phenotype far less tied to severe disability than the classic “Rain Man” picture. The findings highlight a shift in clinical understanding and suggest many health systems, including the United States, may lack capacity to support the expanding, more diverse autistic population. While some will need intensive lifelong assistance, a growing number will require nuanced support for sensory, mental-health and social challenges.