Can a Person Develop Autism After Early Childhood?

How late can symptoms of autism develop?

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There is no official diagnosis called "regressive autism" or "late-onset autism." Yet there are plenty of articles out there about children who appear to regress after their earliest years after developing normally. So does regressive or late-onset autism actually exist? What do we know about it so far?

Neither Older Children Nor Adults Can Develop Autism

To begin with, by definition, older children, teens, and adults do not develop autism.

In fact, in order to qualify for an actual autism spectrum diagnosis, you must have symptoms that appear during early childhood. Thus, if you know an adult or older child who has suddenly, out of the blue, developed behavioral or social communication issues, you are not seeing someone who has acquired autism. That person may have developed any one of a number of other mental health issues, some of which do most commonly appear in early adulthood—but by definition, they are not autistic.

Early-Onset Symptoms May Be Recognized Later in Life

Next, it's important to distinguish between a late RECOGNITION of symptoms and late onset of symptoms. According to the DSM-5 diagnostic criteria: "Symptoms must be present in the early developmental period (but may not become fully manifest until social demands exceed limited capacities, or may be masked by learned strategies in later life)."In the case of high-functioning autism, for example, it's not unusual for a child (or even an adult) to receive a diagnosis much later than most children are diagnosed with autism—but that's not because symptoms suddenly developed.

Rather, the symptoms are so subtle that it's only with time that their impact becomes obvious.

Regression Can Be Real or Apparent

Over the past few years, there has been some debate as to whether regression is a real phenomenon or an apparent one; some have wondered whether parent reports were exaggerated.

Video records, however, combined with studies, make it clear that at least some children do in fact regress into autism while others either show signs of autism in infancy or "plateau" in their development. 

A relatively new set of studies looking at the younger siblings of children with autism in their very earliest months are discovering that subtle regression is quite common. While parents may notice issues such as loss of language or eye contact, researchers are noticing small losses in the areas of motor skills and response to social cues. At present, no one knows exactly what causes regression but, according to at least researcher Paul Wang, “We understand now that regression is common, it starts early, and it can affect many different developmental skills."


S.M. Finegold. "State of the art; microbiology in health and disease. Intestinal bacterial flora in autism." Anaerobe. 2011 Apr 16.

S.M Finegold et al. "Gastrointestinal microflora studies in late-onset autism." Clin Infect Dis. 2002 Sep 1;35(Suppl 1):S6-S16.

Matarazzo. "Treatment of late-onset autism as a consequence of probable autoimmune processes related to chronic bacterial infection." World J Biol Psychiatry. 2002 Jul;3(3):162-6.Study." J Autism Dev Disord. 2006 Apr;36(3):299-316.

J Richler. "Is there a 'regressive phenotype' of Autism Spectrum Disorder associated with the measles-mumps-rubella vaccine? A CPEA.

GA Stefanatos. "Regression in autistic spectrum disorders." Neuropsychol Rev. 2008 Dec;18(4):305-19.

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