A study by researchers at Weill Cornell Medicine, USA, states that autism spectrum disorder (ASD) can be classified into four different subtypes, according to the patient’s brain activity and behavior. This is the first time the groups have been identified, and the discovery was published in Nature magazine on March 9.
By analyzing brain imaging scans of 299 people with autism and 907 neurotypical individuals – without a diagnosis of ASD –, gene expression data and protein interactions, scientists arrived at four patterns of brain connections linked to behavioral traits. Among them: verbal ability, social affect, and repetitive or stereotyped behaviors.
Professor of Psychiatry and Neuroscience Conor Liston, co-senior author of the study, led similar research in 2017 to identify four biologically distinct subtypes of depression. He believes that, with the correct classification of the diagnosis, patients might have a better indication for treatment and, consequently, a better quality of life.
“Like many neuropsychiatric diagnoses, individuals with autism spectrum disorder experience many different types of difficulties with social interaction, communication, and repetitive behaviors,” Liston wrote. “Our work highlights a new approach to discovering subtypes of autism that may one day lead to new approaches to diagnosis and treatment,” she continues.
the groups
According to the scientists, two of the observed groups had above-average verbal intelligence. One of them showed severe deficits in social communication but less repetitive behaviors, while the other showed more repetitive habits and less social impairment.
The researchers explain that the connections between the parts of the brain that process visual information and help the brain to identify the most important information were hyperactive in the group with greater social commitment. On the other hand, these same connections were weak in the group with more repetitive behaviors.
The other two groups had severe social impairments and repetitive behaviors but had verbal skills at opposite ends of the autism spectrum. Despite some behavioral similarities, the researchers found completely different brain wiring patterns in these two subgroups.
Gene analysis
The team analyzed the gene expression that explained the atypical brain connections present in each of the subgroups to understand the cause of the differences in patterns and found that many were genes linked to autism. Furthermore, oxytocin – a hormone linked to positive social interactions – appeared as a core substance in the group of volunteers with greater social engagement but relatively limited repetitive behaviors.
Doctor Amanda Buch, also involved in the study, explains that autism is a highly hereditary condition associated with hundreds of genes that have a diverse presentation and limited therapeutic options. She assesses that one of the barriers to the development of therapies is precisely the breadth of diagnostic criteria that apply to a large and diverse group of people with different underlying biological mechanisms.
“To personalize therapies for individuals with autism, it will be important to understand and address this biological diversity. It is difficult to identify the ideal treatment when everyone is treated as equal, when each one is unique”, says Amanda.
Professor Logan Grosenick of Weill Cornell Medicine agrees. “You might have a treatment that’s working in a subgroup of people with autism, but that benefit disappears in the larger study because you’re not paying attention to the subgroups,” he says.
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