SCIENTISTS ARE close to discovering a gene that significantly increases the risk of a person developing schizophrenia, one of the most common and debilitating mental illnesses.
The results of a 15-year study, involving more than a hundred families and a thousand subjects, has provided researchers with the first definitive evidence that a predisposition to schizophrenia resides on a region of human chromosome 13.
Dr Ann Pulver, an epidemiologist at Johns Hopkins University in Baltimore, said: "Finding the actual gene for schizophrenia susceptibility will be like finding a particular house in a large city.
"But we've found the city. It's a first step, and an exceedingly important one."
The study, published in this month's issue of the journal Nature Genetics, is the first research to provide a genetic "address" for a schizophrenia gene with an internationally accepted degree of statistical reliability.
It has been known for many years that schizophrenia tends to run in families.
Studies of identical twins have shown that if one twin develops the illness, the other has a 46 per cent chance of also becoming a sufferer, which is far higher than the 1 per cent rate for the general population.
"It's not the case that 'you have the gene, you have the disease'. The genetic effect is one of susceptibility to schizophrenia," Dr Pulver said. It is likely that other genes, as well as the influence of the environment or upbringing, also influence the risk of becoming ill, she said.
The scientists analysed the blood samples of 54 schizophrenia patients and samples from members of their families.
By scanning the DNA of the families, the scientists identified a region of chromosome 13 as being implicated in the disease, which was confirmed by a second study of 51 other families with a history of the illness.
Other studies have revealed weak links between schizophrenia and other human chromosomes but this study is the strongest association yet, with the probability of the connection being due to chance alone put at about 2 in 100,000, Dr Pulver said. Dr Karen Schwartz, a member of the research team, said that if the gene on chromosome 13 is found it could revolutionise the understanding of schizophrenia because scientists should be able to understand the precise nature of any chemical imbalance in the brain of patients.
"It will help us to get a more fundamental understanding of the illness. Right now, we just don't understand schizophrenia," she said.
Schizophrenia is a serious problem in Britain, with the illness affecting 1 per cent of the population.
If left untreated, people with schizophrenia experience delusions, hallucinations, incoherent speech and highly disorganised behaviour, which prevents sufferers holding down jobs or looking after themselves.
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