Dr Gina Gómez, from the National Autistic Society, said research into fragile X syndrome could help understanding of certain aspects of autism.

They were aggressive, slow learners, and kept convulsing in seizures-classic signs of Fragile X syndrome.

Fragile X syndrome, a single genetic mutation on the X chromosome, is the most common source of inherited mental impairment, affecting one in every 4,000 boys and one in every 6,000 girls.