This suggests the disorder—already described as an epidemic that affects one in 42 boys—is even more prevalent.
Researchers from Rutgers University's New Jersey Medical School looked at the medical reports of 266,000 children who were eight years of age in 2014 to discover how many showed symptoms of the disorder but who had not been clinically diagnosed.
Of the 4,500 children identified as having autistic symptoms, 25 percent—or one in four—had never been diagnosed. Most of the undiagnosed cases were among black or Hispanic boys.
Symptoms included difficulties with mental abilities, social skills and daily activities—and yet families were not getting any help or assistance to help them cope. Language, communication or cultural barriers could all be playing a part in not getting a diagnosis, the researchers think, and this could be coupled with a fear about stigma of having an autistic child and the complicated diagnosis process.
Early signs of autism could also be incorrectly seen as a behavioural or medical problem, said researcher Walter Zahorodny.
Screening all toddlers, preschool and school-age children could help identify cases that are currently slipping under the radar, and clinicians could overcome language barriers by using pictures to improve communication, he added.