Robert F. Kennedy Jr has reported that there is an epidemic of autism. It is clear that autism is being diagnosed more frequently in the last 10 years, but does that represent an increase in the incidence of autism or better diagnosis? In this post I will review the literature about autism in order to give an evidence-based answer to that question.

Diagnostic Criteria Changes Over Time

There is an excellent paper describing how the criteria for diagnosing autism has changed over time: Update on diagnostic classification in autism. The following information is taken from that paper.

The diagnosis of autism was first described in 1943 by Kanner. Prior to that children with severe autism symptoms were diagnosed as “schizophrenia of childhood.” In 1944 Ausberger reported on a group of children who had similar symptoms to the children Kanner described, but they had no intellectual deficits.

It was not until 1980 that the diagnostic criteria for autistic disorder were included in the Diagnostic and Statistical Manual (DSM)-III). Core features were onset prior to 30 months of age, pervasive lack of responsiveness to others, gross deficiencies in language development, peculiar speech patterns, and bizarre responses to the environment, including resistance to change and fascination with objects. This led to a marked increase in the diagnosis of more severe autism. In 1987, DSM-III-R expanded the menu of symptoms supporting the diagnosis of autism, and formally separated core features into three domains of impairment in social interaction, communication, and restricted or repetitive behaviors.

The next significant change occurred in the DSM -IV in 1994 with the introduction of the diagnosis of Asperger’s disorder. Aspergers’s disorder included what used to be called high functioning autism (autism without intellectual disability). The addition of diagnostic criteria for less severe forms of autism led to another increase in the diagnosis of autism.

In the years since the introduction of the DSM-IV criteria, advances in genetics found that all of the autism disorders had a strong genetic component and that the different forms of autism-like illnesses probably were manifestations of the same condition. In 2013 in DSM V, all of the the autism like illnesses including Asperger’s syndrome were combined into something called autism spectrum disorder.

Subsequent research showed that autism could be diagnosed as early as 18 months of age. This led to the recommendation by the American Academy of Pediatrics that all children should be screened for autism at 18 and 24 months of age. This universal screening has resulted in finding many more cases of autism at an early age that would have been missed previously, or the diagnosis delayed.

Causes of Autism

Genetics is a causal factor in 60%-90% of Autism. Autism is also is associated with prematurity, older parents, low birth weight, air pollution, and perhaps other environmental factors. Autism is not associated with any vaccines or with thimersol. Multiple large well designed studies have found no association between any vaccine, multiple vaccines, and thimersol with autism.

Neurodiversity

An alternate way to view the autism spectrum is not as a disorder, but as an example of neurodiversity. In the neurodiversity perspective, there is natural variation in human brains and minds and there is no single “normal” way to think, learn or behave. Neurodiversity encompasses the wide range of neurological differences, including those often associated with conditions like autism, ADHD, and dyslexia. The neurodiversity paradigm views these differences as strengths and not deficits, promoting acceptance and inclusion of all individuals. Organizations of persons with autism like the Autism Self-Advocacy network promote autism as neurodiversity rather than the medical model of a disorder.

Bottom Line

It is clear that the increased sensitivity to diagnosing autism as well as the universal screening of children at 18 and 24 months has led to the increase in the diagnosis of autism from one in 150 in 2000 to one in 36 in 2020. There is no evidence that there is an epidemic of autism, but rather that diagnosis has improved tremendously. Children on the autism spectrum, even the ones with the severe form of the condition do much better when diagnosed early. There is no cure for autism (and the autism advocacy movement would say that no cure is needed), but the earlier it is diagnosed and interventions begun, the better the long term outcomes.