Three contributing factors
The model links three contributing factors. Together, these result in a pattern of behavior that meets the criteria for an autism diagnosis:
1. Autistic personality — hereditary common genetic variants that give rise to an autistic personality.
2. Cognitive compensation — intelligence and executive functions, such as the capacity to learn, understand others, and adapt to social interactions.
1. Exposure to risk factors — for example, harmful genetic variants, infections, and other random events during gestation and early childhood that adversely affect cognitive ability.
“The autistic personality is associated with both strengths and difficulties in cognition but does not, as such, mean that diagnostic criteria are fulfilled. Still, exposure to risk factors that inhibit people’s cognitive ability may affect their capacity to tackle difficulties, which contributes to individuals being diagnosed with autism,” says Darko Sarovic, physician and postdoctoral researcher at Sahlgrenska Academy, University of Gothenburg, who wrote the thesis.
The model makes it clear that it is the many different risk factors combined that bring about the major differences among individuals on the spectrum. The various components of the model are supported by results from previous research.
High executive functioning skills may enable people to compensate for their impairment in such a way as to mitigate the symptoms, which reduces their risk of meeting the diagnostic criteria for autism. This may explain why, at group level, researchers observe a lower degree of intelligence among people diagnosed with autism, as well as other neurodevelopmental conditions. It also affords an understanding of why intellectual disability is more common among these groups. Thus, the model indicates that low cognitive ability is not part of the autistic personality but, rather, a risk factor that leads to diagnostic criteria being met.
“The autistic personality is associated with various strengths. For example, parents of children with autism are overrepresented among engineers and mathematicians. The parents themselves have probably been able to compensate for their own autistic personality traits and thus not met the criteria for an autism diagnosis. The impact of the disorder has then become more noticeable in their children owing, for instance, to an exposure to risk factors and relatively low cognitive ability,” Sarovic says.
Difference between girls and boys
The diagnosis of autism is more common among boys than girls, and girls often get their diagnosis later in life. Some girls reach adulthood before being diagnosed, after many years of diffuse personal difficulties.
“Girls’ symptoms are often less evident to other people. It’s well known that girls generally have more advanced social skills, which probably means that they’re better at compensating for their own difficulties. Girls also tend to have fewer autistic traits and be less susceptible to the effects of risk factors. Accordingly, the model can help to answer questions about the gender gap,” Sarovic says.
Research and diagnostics
The model also proposes ways of estimating and measuring the three factors (autistic personality, cognitive compensation and exposure to risk factors). This makes it possible to use the model in the planning of research studies and interpretation of their results.
Diagnostics is another conceivable area of use. In a pilot study in which 24 participants had been diagnosed with autism and 22 controls had not, measuring the three factors of the model enabled more than 93 percent to be correctly assigned to the right category. The model can also be used to explain the inception of other neurodevelopmental disorders, such as schizophrenia.
Darko Sarovic is now a postdoctoral research fellow at Harvard Medical School in Boston, Massachusetts, while remaining affiliated to the Gillberg Neuropsychiatry Centre at the University of Gothenburg, Sweden.