A test and possible treatment for autism could be on the horizon after scientists discovered that people and primates who are less social are deficient in a particular hormone.

Around 1.1 per cent of the people in Britain, around 695,000 are through to be on the autism spectrum, according to The National Autistic Society, and although many are able to function well, some find the condition severely debilitating.

Doctors have also struggled to accurately diagnose the condition, but now scientists at Stanford University and The University of California Davis believe that measuring levels of the hormone arginine vasopressin (AVP), which regulates blood pressure, could be the answer.

In tests on rhesus monkeys, they found that less social animals had levels of the hormone which were almost one third lower than their more gregarious peers. And a similar deficiency was found in 14 autistic boys.

Although the results are preliminary, the researchers believe their findings suggest that AVP may not only provide a test for autism, but also be a target for developing drugs to alleviate social impairment.

"Since autism affects the brain, it's really hard to access the biology of the condition to know what might be altered," said Dr Karen Parker, associate professor of psychiatry and behavioral sciences at Stanford and the lead author of the new study.