Researchers said Thursday they had discovered a genetic mutation in people with autism that cuts communication between brain cells to about one-tenth of normal levels.
The study found a protein which helps brain cells transfer data through neurological pathways called synapses was mutated in autism sufferers, offering a likely explanation for their cognitive and behavioural difficulties.
Principal investigator Johanna Montgomery, from Auckland University's Centre for Brain Research, said the mutated protein, called Shank3, provided exciting possibilities in the search for autism treatments.
"(A treatment) is years away," she told AFP. "But we now know how it works, we know what goes wrong, so let's try to figure out a way to fix it.
"Now we've got a focus for how we actually rescue this protein, to make it work appropriately again so that brain cells can communicate at the right levels."
The two-year study, published in The Journal of Neuroscience, was carried out by the Centre for Brain Research and Stanford University in the United States.
Montgomery said researchers were beginning to understand the complex factors behind so-called autism spectrum disorders (ASD), which typically result in learning difficulties, lack of socialisation and repetitive behaviours.
She said the condition was becoming more prevalent, partly due to more efficient diagnosis, with studies estimating it affects about one-in-82 children.