A 15-year study in more than 100 families and 1,000 subjects provides the first reliable evidence of genetic susceptibility to schizophrenia, within a stretch of DNA on human chromosome 13. The association of DNA with the susceptibility to the disease, reported by a Johns Hopkins-led international team, is the first such linkage to meet stringent statistical standards. But we've found the city. It's a first step, and an exceedingly important one. The study, reported in this month's Nature Genetics, also suggests that different genes may be responsible for the disease in different families.
Most experts agree schizophrenia is a condition influenced by both genes and environment.
In studies of identical twins, for example, where only one twin develops schizophrenia, the other twin has a 46 percent chance of having the disorder. That's higher than the 1 percent rate for the general population but not the near-100 percent expected if genes are the only cause. The genetic effect is one of susceptibility to schizophrenia. Unlike such inherited disorders as sickle cell anemia, which stems from mutation in a single gene, susceptibility to schizophrenia involves more than one gene, Pulver says, as well as environmental factors. In the new study, the researchers carefully evaluated and took blood samples from 54 patients diagnosed with either schizophrenia or with schizoaffective disorder, a type of schizophrenia with elements of depression, mania or both.