Natural cannabis-like chemicals in the brain may help combat the leading genetic cause of autism, research has shown.
Scientists linked blockages in a signalling pathway dependent on the compounds, called 2-AG endocannabinoid transmitters, with symptoms of Fragile X syndrome.
Correcting the fault with drugs led to dramatic behavioural improvements in mice with a version of the condition.
Fragile X syndrome is the most common known genetic cause of autism.
It results from a mutation in the FMR1 gene on the female X chromosome. Men possess one copy of the chromosome, paired with a male Y chromosome, and women two.
Boys are much more likely to be born with Fragile X than girls. This is thought to be because with two X chromosomes, a defect in one may be compensated for by the other.
People with the syndrome suffer mental impairment, learning difficulties, and may be hyperactive or impulsive. They also possess notable physical characteristics such as an elongated face, flat feet and large ears.
The scientists, writing in the journal Nature Communications, stress that while their discovery may help people with Fragile X syndrome it will not provide a cure.
"What we hope is to one day increase the ability of people with Fragile X syndrome to socialise and engage in normal cognitive functions," said lead researcher Professor Daniele Piomelli, from the University of California at Irvine in the United States.
The study was the first to identify the role of endocannabinoids in the neurobiology of Fragile X, she said.
Endocannabinoid compounds are created naturally in the body and share a similar chemical structure with THC, the primary psychoactive component of the marijuana plant, Cannabis.
Endocannabinoids are distinctive because they link with protein molecule receptors -- called cannabinoid receptors -- on the surface of cells. For instance, when a person smokes marijuana, the cannabinoid THC activates these receptors. And because the body's natural cannabinoids control a variety of factors -- such as pain, mood and appetite -- they're attractive targets for drug discovery and development.
Piomelli is one of the world's leading endocannabinoid researchers. His groundbreaking work is showing that this system can be exploited by new treatments to combat anxiety, pain, depression