The gene that likely makes people left-handed may slightly raise the risk of developing psychotic mental illnesses, according to an international study.

Led by the Wellcome Trust for Human Genetics at the University of Oxford, the study involves a team of 40 scientists from 20 research centres across the world, and was published online Tuesday in the scientific journal Molecular Psychiatry.

"This is the first potential genetic influence on human handedness to be identified, and the first putative genetic effect on variability in human brain asymmetry," said an abstract on the study.

The scientists said that little is known about the gene LRRTM1, but they suspect that it modifies symmetry in the human brain. Asymmetry is important, since the left side of the brain usually controls speech and language and the right side controls emotion. With left-handers this pattern is often reversed.

The researchers suspect that the same gene might slightly increase the risk of developing schizophrenia — a disorder of the brain that often results in impaired perception and thought that affects roughly one per cent of adults worldwide.

Like left-handers, people with schizophrenia also often have unusual patterns of brain asymmetry.

The study leader, Dr. Clyde Francks, said in a statement, “People really should not be concerned by this result. There are many factors which make individuals more likely to develop schizophrenia and the vast majority of left-handers will never develop a problem. We don’t yet know the precise role of this gene.”

Some of the study's researchers plan to further investigate the roles of LRRTM1 in the developing brain, and to find other genes with which it interacts. 

“We hope this study’s findings will help us to understand the development of asymmetry in the brain. Asymmetry is a fundamental feature of the human brain that is disrupted in many psychiatric conditions,” added Dr. Francks.

Roughly 10 per cent of people are left-handed. Last year, Australian researchers suggested that left-handers can think more quickly when it comes to tasks such as playing computer games or playing sports.