Autism with out mental impairments extra widespread than beforehand reported | Spectrum
Screening skew: Autistic people with a below-average IQ can be more easily recognized by clinicians.
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More than half of autistic people in the United States have average or above average intelligence quotient (IQ), an increase from previous estimates, a new longitudinal study of children in Minnesota suggests.
The increase could reflect increased awareness and understanding of the disease, as well as improvements in detection and detection, says lead investigator Maja Katusic, a developmental pediatrician at the Mayo Clinic in Rochester, Minnesota.
In 2016, the percentage of autistic children in the US with an average or higher IQ was 42 percent, according to the latest autism prevalence data released in 2020 by the Centers for Disease and Control and Prevention (CDC).
However, the new study suggests that this number could be as high as 59 percent.
Katusic and her colleagues searched a treasure trove of medical and educational records from more than 30,000 people born between 1976 and 2000 in Olmsted County, Minnesota. They identified people with autism based on behavioral ratings and descriptions in the records, using either a broad or narrow definition of the condition in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). The inclusive definition identified children who met the criteria for autistic disorder, Asperger’s syndrome or pervasive developmental disorder – not otherwise specified – while the narrow definition only included those with autistic disorder. The researchers also totaled the clinical diagnoses of autism documented in the records.
Of the 890 people whose records included IQ data and who met the inclusive definition of autism, 59 percent had an average or higher IQ score – defined in the study as 86 or higher. The same was true for 51 percent of the 453 people who met the narrow definition. In contrast, of the 187 people with a clinical diagnosis, only 43 percent had mean or higher IQ scores. The study appeared in Pediatrics in November.
Findings suggest that autistic people with below-average IQs are more easily identified by clinicians – and that people with higher IQs are more likely to be overlooked and potentially miss out on services that would benefit them.
“[Autistic] People with an average IQ or higher can still have difficulties with relationships, finding and keeping jobs with activities of daily living, ”says Katusic.
In all three diagnostic groups, a greater proportion of autistic boys had an average or higher IQ than autistic girls. Autistic girls tend to be diagnosed later in life and hide their characteristics, Katusic said, which may help explain this gender divide.
“Maybe women with autism [who have an] average to high IQs may be better at hiding some of their social communication difficulties and may not meet all of the criteria for autism, ”she says.
There are several important caveats to the results. For example, more than 90 percent of the participants are white and highly educated, so the results may not necessarily apply to a wider population.
IQ is also important, says Katusic, but it doesn’t capture the “adaptive skills” of autistic people: practical, everyday skills like caring for yourself, participating in activities, and generally being able to function in a community.
In the future, Katusic hopes to deepen these skills and examine the gender-specific IQ differences more closely.
