Why autistic people often avoid hugs from loved ones

Researchers found those with Fragile-X syndrome had delayed development in the brain region that responds to touch

Doctors believe they may have discovered why many people with autism don't like to be touched or hugged even by their parents.

They studied individuals with Fragile X Syndrome, a well-known genetic cause of autism.

It is also the most common known cause of inherited learning disabilities.

The scientists found Fragile X results in delayed development of the sensory cortex, the brain region that responds to touch.

A domino effect triggered by the delay may cause this part of the brain to be wrongly wired.

Fragile X is caused by a gene mutation in the female X chromosome that affects the construction of synapses, vital connection points between nerve cells.

Because boys have only one X chromosome, they are more severely affected by the syndrome than girls.

As girls have two X chromosomes it makes less impact if one is defective. Boys are generally more likely to develop autism than girls.

The U.S. scientists, writing in the journal Neuron, studied mice with their own version of Fragile X. They discovered that the mutation in the affected animals blocked the production of a protein that directed other synapse-building proteins.

This meant the development of synapses was delayed in the sensory cortex.

'There is a critical period during late development when the brain is very plastic and is changing rapidly,' said study leader Dr Anis Contractor, from Northwestern University.

'All the elements of this rapid development have to be co-ordinated so that the brain becomes wired correctly and therefore functions properly.'

People with the syndrome suffer from 'tactile defensiveness' and become anxious and socially withdrawn, said Dr Contractor.

She added: 'They don't look in people's eyes, they won't hug their parents, and they are hypersensitive to touch and sound.

'All of this causes anxiety for family and friends as well as for the Fragile X patients themselves. Now we have the first understanding of what goes wrong in the brain.'

The research raises the possibility of intervening at the right time in a child's development to prevent the problem.

For more information on Fragile X syndrome visit The Fragile X Society's website

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