Scientists have discovered a variation in a gene in people at risk of schizophrenia that strongly suggests they will develop the condition. Brain scans of young people predisposed to schizophrenia show that those who go on to develop the symptoms of the disorder have the mutated gene.

While this does not mean scientists have found a "gene for schizophrenia", it provides strong evidence of a key genetic link and brings them one step closer to finding a cure. Last night, the mental health charity Sane described the research as exciting, and referred to the possibility of a breakthrough.

The researchers, from the University of Edinburgh, made their discovery after following 163 young people at risk of developing schizophrenia from their late teens for 10 years. Schizophrenia has a strong inherited element, and all the participants in the project - known as the Edinburgh High Risk Study - had two or more relatives who had developed the condition.

The researchers, who report their results in the journal Nature Neuroscience, found that there was a clear link between one particular variation of the neuregulin gene - which is involved in the development of the mind and the wiring of the brain - and the risk of developing psychotic symptoms. People with this genetic variation were almost three times as likely to develop the symptoms of schizophrenia - with 100% going on to develop them, compared with 40% of participants across the study - a result viewed as "highly statistically significant".

While it is known that neuregulin is associated with schizophrenia, the research, funded by the Medical Research Council and led by Eve Johnstone, professor of psychiatry at the University of Edinburgh, is the first to pinpoint the genetic variant responsible. Jeremy Hall, a psychiatry lecturer at the university, and the study's lead author, said: "We think this is a breakthrough." Prof Johnstone praised the "altruism and courage" of the participants - some of whom knew they might be developing the illness.