Scientists have identified 50 new gene regions that increase the risk of developing schizophrenia, a finding that could lead to improved treatment for the debilitating psychiatric condition that affects over 20 million people worldwide.

The study showed that some of the genes identified as increasing risk for schizophrenia have previously been associated with other neurodevelopmental disorders, including intellectual disability and autism spectrum disorders. "These findings are another important step on the long road to new treatments for schizophrenia and will be crucial for identifying potential new drugs, which will become an increasing focus of our work in the coming years," said Mike Owen, Professor at the Cardiff University.

For the study, published in the journal Nature Genetics, the team examined genetic data in 100,000 individuals including 40,000 people with a diagnosis of schizophrenia. They also found that the genes linked to schizophrenia risk are mostly crucial to normal development and therefore typically do not contain harmful mutations. This discovery will help researchers narrow down their search for the mechanisms of the disorder as these genes, commonly called "loss-of-function intolerant", only account for around 15 per cent of all the genes in the human genome.

"We show, for the first time, that genetic variants that do not severely impact gene function, but presumably have a more subtle impact on these critical genes, increase risk for developing schizophrenia," said Antonio Pardinas, from the varsity. Moreover, the findings have solved a mystery that puzzled psychiatrists and evolutionary geneticists -- why does schizophrenia affect so many people when on average they have fewer children than people without the disorder? "We found that many gene variants linked to schizophrenia reside in regions of the genome in which natural selection is not very effective in the first place," explained James Walters, another researcher from the varsity. "Also, most of them do not have individually serious effects, and this makes them less likely to be selected, either for or against," he noted.