A widely used diabetes medication could help people with a common inherited form of autism, research shows.

Scientists found that a drug called metformin improves sociability and reduces symptomatic behaviours in adult mice with a form of Fragile X syndrome.

Researchers say that metformin could be repurposed as a therapy for Fragile X syndrome within a few years – if clinical trials prove successful.

Fragile X syndrome is caused by inherited defects in a gene called FMR1, which leads to excess protein production in the brain.

This results in the breakdown of connections between brain cells, leading to changes in behaviour.

The team led by the University of Edinburgh and McGill University in Canada looked at the effects of metformin on mice that lack the FMR1 gene.

These mice usually have symptoms consistent with Fragile X syndrome – they exhibit repetitive behaviours such as increased grooming and do not socialise with other mice. After mice had treatment with metformin for ten days, protein production in the brain returned to typical levels, brain connections were repaired and they displayed normal behaviour patterns, the researchers found.

The therapy also reduced the occurrence of seizures, which are reported to affect between 10 and 20 per cent of people with Fragile X.

"Metformin has been extensively used as a therapy for type 2 diabetes for more than 30 years, and its safety and tolerability are well documented. Our study suggests the drug could be a novel therapeutic for Fragile X syndrome, a common type of autism," said Dr Christos Gkogkas, Wellcome Trust Sir Henry Dale Fellow in the University of Edinburgh’s Patrick Wild Centre.

Researchers say they next plan to investigate whether the drug offers any benefits for other types of autism.

The study was published in the journal Nature Medicine.