Autism Manifests at 6 to 12 Months

Steve Novella at Science Based Medicine:

There has been much debate about the early course of autism, specifically the earliest age at which autism may be detected. At present scientific evidence suggests that autism is dominantly genetic, and so researchers expect that there may be early signs of autism even in infancy. Traditionally, however, autism is not diagnosed until age 2-3, when parents bring their children to medical attention, or when signs are detected on routine well-child visits or in day-care.

Retrospective studies, largely involving review of home movies, have suggested that autism can be diagnosed as early as 6-12 months, suggesting that parental report is not an adequate screen because subtle signs are hard to detect without rigorous observation.

Now a group has published the first prospective study to address this question. They followed 25 children who were later diagnosed with autism spectrum disorder (ASD) (22 of which were high risk) and 25 low risk children who were later determined to have typical development (TD). They found:

These results suggest that behavioral signs of autism are not present at birth, as once suggested by Kanner, but emerge over time through a process of diminishment of key social communication behaviors. More children may present with a regressive course than previously thought, but parent report methods do not capture this phenomenon well. Implications for onset classification systems and clinical screening are also discussed.

More precisely, they carefully assessed the children, counting instances of eye contact and smiling, for example, and found that there were no statistically significant differences between the groups at 6 months, but that almost all measures were reduced in the ASD group by 12 months.