Scientists say they have conclusive evidence that changes to a gene called SETD1A can dramatically raise the risk of developing schizophrenia - a finding that should help the search for new treatments.
The team, led by researchers at Britain's Wellcome Trust Sanger Institute, said damaging changes to the gene happen very rarely but can increase the risk of schizophrenia 35-fold.
Changes in SETD1A also raise the risk of a range of neurodevelopmental disorders, the researchers said.
In a study published in the journal Nature Neuroscience, the team found that mutations that remove the function of SETD1A are almost never found in the general population, but affect one in 1000 people with schizophrenia.
Schizophrenia is a severe and common psychiatric illness that affects around one in 100 people worldwide.
Symptoms include disruptions in thinking, language and perception, and patients can also suffer psychotic episodes.
The exact causes of schizophrenia are unknown, but research to date suggests a combination of physical, genetic, psychological and environmental factors can make people more likely to develop it.
Jeff Barrett, who led the study for the Sanger Institute, said its results were surprising and exciting.
"Psychiatric disorders are complex diseases involving many genes, and it is extremely difficult to find conclusive proof of the importance of a single gene," he said.
Mike Owen, a Cardiff University expert in neuropsychiatric genetics and genomics, said the so-far limited understanding of schizophrenia's causes has hampered efforts to develop new treatments.
This new finding about the gene may guide researchers towards new pathways that could be targets for treatments or medicines, Owen said.
The study analysed the genome sequences of more than 16,000 people from Britain, Finland and Sweden, including those from 5,341 people with schizophrenia.
Damage to the SETD1A gene was found in 10 of the schizophrenia patients, and surprisingly also in six other people with other developmental and neuropsychiatric disorders.
