DNA analysis of thousands of people in three separate studies has shown that the disorder is linked to the interaction of a large number of genetic variants on chromosome 6, in an area called the Major Histocompatability Complex which has one role in the immune system and another in controlling the switching on or off of other genes.

How many variants are there? Well, over 30,000 were identified as being much more common in schizophrenics than non-schizophrenics apart from people with bipolar disorder.

So not only is the genetics of schizophrenia far more complex than had been thought, environmental influences are also involved, but there could be a previously unexpected overlap between the two psychopathologies, schizophrenia and bipolar disorder (manic depression).