The development of autism may now be easier to understand, thanks to an explanatory model presented in a thesis from the University of Gothenburg, Sweden. This model provides new insights into how various risk factors lead to autism and why there is great variability between individuals.
Autism, a neurodevelopmental condition, affects how people perceive the world around them and how they interact and communicate with others. Among people with autism, there are great differences in terms of personal traits and manifestations. Therefore, the disorder is typically described as a spectrum, with numerous subtle variations.
The new explanatory model is theoretical but at the same time practical in application, since its different components are measurable through, for example, questionnaires, genetic maps and psychological tests. The model describes several contributing factors and how they combine to lead to a diagnosis of autism and cause other neurodevelopmental conditions.
Three contributing factors
The model links three contributing factors. Together, they result in a pattern of behavior that meets the criteria for a diagnosis of autism:
1. Autistic Personality: Common inherited genetic variants that result in an autistic personality.
2. Cognitive compensation: intelligence and executive functions, such as the ability to learn, understand others, and adapt to social interactions.
3. Exposure to risk factors, for example, harmful genetic variants, infections, and other random events during gestation and early childhood that adversely affect cognitive ability.
Autistic personality is associated with both strengths and cognitive difficulties, but as such does not mean that diagnostic criteria are met. However, exposure to risk factors that inhibit people’s cognitive ability can affect their ability to cope with difficulties, which contributes to people being diagnosed with autism.”
Darko Sarovic, doctor and postdoctoral researcher at the Sahlgrenska Academy, University of Gothenburg
The model makes it clear that it is the many different risk factors combined that cause the major differences between individuals on the spectrum. The different components of the model are supported by the results of previous research.
Adaptive capacity
High executive functioning skills may allow individuals to compensate for their impairment in ways that mitigate symptoms, thereby reducing the risk of meeting diagnostic criteria for autism. This may explain why, at the group level, researchers observe a lower degree of intelligence among people diagnosed with autism, as well as other neurodevelopmental conditions. It also helps to understand 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 causes the diagnostic criteria to be met.
“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 therefore do not meet the criteria for an autism diagnosis. The impact of the disorder has become more noticeable in their children due to, for example, exposure to risk factors and relatively low cognitive ability,” says Sarovic.
Difference between girls and boys
A diagnosis of autism is more common among boys than among girls, and girls often receive their diagnosis later in life. Some girls reach adulthood before being diagnosed, after many years of diffuse personal difficulties.
“Girls’ symptoms are often less obvious to other people. It is well known that girls generally have more advanced social skills, which probably means they are better at compensating for their own difficulties. Girls also tend to have fewer traits autistics and be less susceptible to the effects of risk factors. Consequently, the model can help answer questions about the gender gap,” says Sarovic.
Research and diagnosis
The model also proposes ways to estimate and measure the three factors (autistic personality, cognitive compensation, and exposure to risk factors). This allows the model to be used in the planning of research studies and the interpretation of their results.
Diagnostics is another area of conceivable use. In a pilot study in which 24 participants had been diagnosed with autism and 22 controls had not, measuring all three factors in the model correctly assigned more than 93 percent to the correct category. The model can also be used to explain the onset of other neurodevelopmental disorders, such as schizophrenia.
Darko Sarovic is now a postdoctoral researcher at Harvard Medical School in Boston, Massachusetts, although he remains affiliated with the Gillberg Neuropsychiatry Center at the University of Gothenburg, Sweden.