A majority of genetic risk factors associated with autism spectrum disorders (ASD) can be found in the general population, scientists claim.
Though it is unclear how the presence of such genetic factors manifests itself in healthy people, they are believed to influence on a range of behavioural and developmental traits. The study's authors, who publish their conclusions in Nature Genetics, say that people diagnosed with ASD are simply displaying a more severe manifestation of behaviour traits that can be present in everyone. In other words, we might all carry some of the genetic signs of ASD, but they might not manifests themselves in the same degree.
The team of scientists, which regrouped academics from the University of Bristol, the Broad Institute of Harvard and MIT, and Massachusetts General Hospital (MGH), analysed the data taken from different cohorts, which included both healthy individuals and patients suffering from ASD. They had access a lot of different genetic information as well as physical and behavioural characteristics.
The scientists discovered that some genetic risk factors for ASD were found on a very frequent basis in unaffected persons.
In their research paper, they mention for example a genetic mutation called 16p11.2, which is an important risk factor of ASD. They observe is also very common amongst individuals who are not diagnosed with the disorder. 16p11.2 has a quantitative effect on intelligence, resulting in a loss of IQ points in children compared to their parents.
The authors note that "traditional categorical psychiatric diagnoses (for example, yes/no for ASD) ignore the possibility of intermediate outcomes". With this study, the scientists show that individuals who are not diagnosed with the disorder can still have some ASD risk factors affecting them in their daily lives, such as this loss in IQ points. This is despite them not showing any other signs of autistic behaviours.
"Our study suggests we move from a binary opposition between having the disorder or not having it all", co-author Professor George Davey Smith told IBTimes UK.
The researchers expect their reflection regarding the associations between genetic risk and behavioural traits to be applied to other types of neuropsychiatric disorders, such as schizophrenia, in the future.