SAN DIEGO – Autism spectrum disorder can be reliably diagnosed in children as young as 14 months, said a study by the University of California, San Diego. If results are confirmed by independent research, this would be the earliest age this has proven feasible.

Earlier detection means earlier treatment, which should improve outcomes, said Karen Pierce, co-director of the UCSD Autism Center for Excellence. Pierce led the study published in JAMA Pediatrics with co-director Eric Courchesne.

Autism screening should be first done at 18 months, said the American Academy of Pediatrics. However, the Centers for Disease Control and Prevention said the average age of diagnosis in the U.S. is 4 years. That gap represents a missed opportunity, Pierce said.

"The brain is very plastic. It's developing at a really super-fast pace from birth to age 3," she said. "There's a lot of connections that are formed between brain cells. So hopefully we can shape those connections."

Results are based on the development of 1,269 toddlers, selected from a universal screening program to detect possible autism. Children suspected of having ASD via screening were referred for a developmental evaluation by a licensed clinician to determine whether they actually had autism or some other disorder.

The toddlers were assessed between 12 and 36 months, and had at least one follow-up evaluation. For those whose autism was diagnosed at 14 months, 79 percent were again found to be on the spectrum at follow-up. By 16 months, the diagnosis was 83% reliable. However, for those who had the disorder diagnosed at 12 to 13 months, the rate was just 50%.

The research was funded in part, by the National Institute of Mental Health, part of the National Institutes of Health.