Schizophrenia affects approximately 1% of the world's population. About 40% of cases are thought to be inherited with the other 60% occuring spontaneously in people with no family history of the disease. A study of 1,077 people from the Afrikaner population in South Africa found that rare, spontaneous genetic mutations accounted for at least 10% of the non-familial cases of the disease. The researchers found mutations, either a gain or loss of genes, in 15 individuals diagnosed with schizophrenia that were not present in the chromosomes of either biological, unaffected parent. Chromosome 22 was found to be particularly significant.
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