As many as 30,000 different gene variations may underlie schizophrenia and bipolar disease, meaning any kind of quick test to predict either disease is a long way off

Three studies by a multinational group of researchers analyzed the DNA of 10,000 people with schizophrenia, and 20,000 without, and found 30,000 common gene variations linked with the mental illness

The scientists stressed that although the large scale of the combined studies meant their results were robust as building blocks, they could not be used yet to predict an individual's risk of developing the disease

Previous scientific studies have already identified a genetic basis to schizophrenia and suggested that rather than one crucial gene being responsible for the disorder, a large number of genes and genetic combinations could cause it