And given that autism can only be diagnosed based upon behaviour rather than medical testing, they say the true figure could be closer to one in 200 as signs in some children may be so slight they were overlooked.

Experts have been carrying out diagnostic examinations on children aged between 18 months and two years in Salamanca, Zamora and Madrid, in an attempt to find out whether unusual conditions can be discovered at a much younger age and the relevant therapy started earlier on in their formative years.

Autism diagnosis and treatment has dramatically improved in recent years and the condition is much more widely-known about and understood, says Manuel Posada, head of the Institute of Rare Illnesses at the university.

Just a few days ago, the national support group for parents of autistic children managed to get the definition of 'autism' changed in the Spanish dictionary.

Until then, the Royal Spanish Academy (RAE), the producers of Spain's equivalent of the Oxford English dictionary, had defined it as a condition where those affected were 'incapable' of 'showing affection' or of 'giving and feeling love'.

This made it terribly upsetting for parents who found out their children were autistic, since they believed that their own child would never be able to love them.

However, this is not necessarily the case, since the correct medical definition relates more to serious problems in relating to other humans, and an inability to understand anything other than direct and straightforward language.

Autistic children and adults do not understand irony, cannot 'read between the lines' and are unable to 'read' facial expressions.

Early warning signs often relate to a delay in learning to speak, but where this is not the case, parents say their children do not react when called by name or when given orders or instructions, prefer to play alone and in a very repetitive fashion, and do not react to emotions or physical contact.