In April, Jon McClellan at the University of Washington in Seattle and his colleagues confirmed that schizophrenia is largely genetic in origin, and found many individually rare mutations that make a person more likely to develop it. Scientists had thought that the combined effects of common variants were responsible.
The team analysed the DNA of 150 individuals with schizophrenia and 83 with childhood-onset schizophrenia, searching their subjects' genomes for rare deletions and duplications that disrupt genes. These were much more common in the genomes of people with schizophrenia than in those of healthy controls. Most schizophrenia patients had mutations that others did not have but that tended to be in the same genes. The genes altered by these mutations were disproportionately involved in neurodevelopmental pathways.