The Trump administration has falsely suggested, with no scientific basis, that autism is linked to measles vaccination and paracetamol. Leaving aside these highly criticized claims, what are the actual scientific facts about autism spectrum disorder?
#1- Do people with autism all have the same symptoms?
No. The presentation of autism spectrum disorder is highly variable.
Autism is a neurodevelopmental disorder (NDD). It presents in early childhood, before the age of 36 months, and affects children's development in different ways and to different degrees. The scientific and medical community agree that autism symptoms can be broadly divided into two categories: atypicalities in social communication and interaction, and the presence of restricted or repetitive behaviors, activities or interests.
Autism symptoms vary considerably from one person to the next. In the words of British psychiatrist Lorna Wing: "When you have seen one person with autism, you have seen one person with autism."
So there is not a single profile for people with autism, but a series of very different profiles, with a wide range of difficulties.
These wide-ranging symptoms, and the different profiles of autism depending on the age at diagnosis, were highlighted in a recent international study coordinated by the University of Cambridge, in connection with the R2D2-MH consortium led by the Institut Pasteur. The research shows that the genetic profiles of autistic people with later diagnosis (after the age of 10) differ from those of autistic people diagnosed earlier. Autism is a condition with considerable clinical and genetic heterogeneity.
#2-What causes autism spectrum disorder?
Autism spectrum disorder (ASD) has many causes, and there is a strong genetic component. Neither measles vaccination nor paracetamol causes ASD.
The US authorities recently suggested that autism is linked to the measles vaccine and to paracetamol. US President Donald Trump advised pregnant women to avoid taking paracetamol and the US Secretary of State for Health, Robert F. Kennedy Jr., has called into question the safety of the measles, mumps and rubella (MMR) vaccine on several occasions.
But no serious scientific studies have found a link between autism and paracetamol, or autism and the MMR vaccine.
The causes of ASD are primarily genetic.
The genetic characteristics associated with autism are extremely complex. Since the first genes associated with autism were discovered in 2003 by Thomas Bourgeron's team at the Institut Pasteur, more than 200 genes have been identified. In some cases, a single genetic variation can result in autism. This is known as monogenic autism. In others, the cumulative effect of thousands of genetic variations increases the likelihood of ASD, a phenomenon known as polygenic autism. The genes involved tend to be linked to neurodevelopment and connections between neurons. Many genes associated with autism encode proteins in synapses, in other words the contact points between neurons.
There are also other factors. It has been proven that taking epilepsy medication like sodium valproate (Depakine®, Depakote®, Depamide®, Micropakine® and generic brands) during pregnancy increases the likelihood that the child will go on to develop autism. Perinatal complications and premature birth can also play a role in the emergence of ASD.
#3- Can we say that there is an "autism epidemic"?
No. There is a rise in the number of people being diagnosed but there is not an autism epidemic.
In spring 2025, Robert F. Kennedy Jr. launched a "testing and research effort" to shed light on what he referred to as the ongoing "autism epidemic." The main reason for the initiative is the rise in the number of people diagnosed with ASD in the United States since 2000.
But that does not mean that we are witnessing an "autism epidemic." It is important to distinguish between the number of actual cases and the number of diagnosed cases.
The rise in the number of people with ASD can be explained by better detection and diagnosis and an expanded definition of the diagnostic criteria.
Until recently, for example, people with what was once called "Asperger's syndrome," characterized by relational difficulties but few or no cognitive difficulties, were very rarely diagnosed with autism. Moreover, since the publication in 2013 of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the key reference book classifying mental disorders, it has been possible to diagnose individuals with both autism and attention-deficit/hyperactivity disorder (ADHD), which was not previously the case. Now that people can now be given a dual diagnosis, we are seeing greater precision and the inclusion of more autistic people with ADHD. This also applies to people with intellectual disability (ID). Many people who previously had a diagnosis of ID on its own now have a diagnosis of autism with ID.
More attention is now paid to the social difficulties, restricted interests and characteristic stereotyped movements associated with autism. In general, autism is considered as a varied disorder, with mild or more marked symptoms. Taking this variability into account has naturally led to an increase in the number of people diagnosed with autism.
As Thomas Bourgeron explained in his book Des gènes, des synapses, des autismes, "[…] before the year 2000, two-thirds of people diagnosed with autism had an intellectual disability. In 2022, the opposite is true."
Based on the most recent diagnostic criteria, it is currently thought that between 1 and 2.3% of the population could have ASD.
Sources: Polygenic and developmental profiles of autism differ by age at diagnosis, Nature, October 1, 2025
Des gènes, des synapses, des autismes. Thomas Bourgeron.
The Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR), published by the American Psychiatric Association, describes and classifies mental disorders, including autism. Although criticized, the manual remains largely used. Since 2013, it has included people previously diagnosed with Asperger's syndrome under the umbrella of ASD.
