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Genetic Link between Diagnoses of Autism and Tourette Syndrome

Through our research on diagnoses of autism at Small Steps Big Dreams in Dubai, UAE, we see that the genetic variants that contribute to autism can also be seen in Tourette syndrome and ADHD.

What is Tourette Syndrome

Tourette syndrome (also called Tourette’s syndrome, and shortened as Tourette’s or TS) is a condition that can cause a person to make uncontrolled movements and sounds, which are called tics; and they can include eye blinking, throat clearing, and facial movements, etc.

A relevant study conducted in 2019 saw researchers from the Psychiatric Genomics Consortium link factors associated with Autism Spectrum Disorder to seven different neuropsychiatric conditions. The list comprised of- among others- anorexia, bipolar disorder and schizophrenia. It had been observed that more than half the people with Tourette’s also have obsessive-compulsive disorder (OCD) or ADHD, and up to 20% have autism. Because all four conditions tend to be associated with impulsive and/or compulsive behaviours, some scientists have proposed that they exist along a spectrum: ADHD on one end, OCD on the other, and autism and Tourette’s in the middle.

Autism Spectrum Disorder and Tourette syndrome

The Similarities

Both Tourette syndrome and ASD are conditions that begin during childhood, mostly affecting males. The male to female ratio is approximately 3:1 in Tourette’s, and 7:1 in ASD. As well as similarities in terms of prevalence and gender ratio, research has found that there is a significant proportion of TS patients who also have autism.

Cognitive ability in children of determination can range from profound disability to superior intelligence. However, Tourette syndrome does not affect cognitive ability; yet it can affect children’s learning. After all, concentrating on a lesson can be challenging if a child is trying to manage their tics.

Some research carried out by way of improving autism treatment in Dubai show that about 2% of individuals with Tourette syndrome have Copy Number Varients (also known as CNVs)- rare repetitions or removals of chunks of chromosomes.  This disrupts the ‘ASD implicated’ (genes or genomic regions significantly implicated in ASD), compared to only 0.4% of the controls who were part of the study. And almost twice as many individuals with the syndrome have CNVs that disrupt either ‘ASD implicated’ or ‘autism candidate’ (displaying some connection with ASD) genes than did the controls: 10.2% compared to 5.7%.

Mental health can also be an issue for either an autistic child or someone suffering from Tourette, e.g. issues with depression, anxiety and anger etc. Consequently, in essence, having TS and being in school can increase anxiety, and will no doubt also increase tics.

Researchers have suggested that Covid-19 might increase mental health difficulties disproportionately in people with tic disorders, and we can imagine this might also be the same for individuals with ASD. In particular, some individuals with tic disorders also have vocal tics which look very similar to some Covid-19 symptoms, like a dry cough, clearing the throat and/or sniffing.

The Differences

However, some factors set these two disorders apart. For starters, the causes behind the movement-associated symptoms of TS and ASD are different. For Tourette’s, physical tics are involuntary, usually accompanied by a physical sensation (premonitory urge) before the tic. In autism, movements are called stereotypies. The onset of these stereotypies occurs at earlier ages (<2 years) than tics (6/7 years).

Stereotypies are more constant in time and pattern, whereas tics wax and wane over time. Tics tend to be rapid and random; whereas stereotypies are more rhythmic, often involving flapping and waving.

People with autism are more likely to hurt themselves than those with Tourette syndrome. Eye poking and skin picking are rare behaviours in a person with TS, but more common with an autistic child. Children with a diagnosis of autism also typically exhibit unusual eating behaviour, which is not typically seen in those with Tourette’s.

The Genetic Link between Autism and Tourette’s

The study is “very powerful,” says Tinca Polderman, associate Professor of Child and Adolescent Psychiatry at Amsterdam UMC in the Netherlands.  She was not involved in the research; however, she states that this focus on genetic link to each condition may ultimately point to new treatment targets. Polderman also stated that better care for those with diagnoses of autism and Tourette’s can be achieved with more insight. It is the understanding of those at Small Steps Big Dreams in Dubai, UAE, therefore that understanding, awareness and acceptance will help all people with differences to the point where society can hopefully look away from the stereotypes and stigma about Tourette Syndrome and Autism Spectrum Disorder.

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