'However, attempts to understand how genes contribute to the symptoms that patients experience reveal how complex – and poorly understood – the human brain is.
'Schizophrenia affects about 1 in 100 people and patients can suffer from hallucinations, delusions and problems with social interactions. There is no cure and although drugs are available that treat some of the symptoms they can have unpleasant side effects, and they don’t work for everyone.
'Schizophrenia results from both genetic and environmental factors. Our genes influence brain development to make us more or less sensitive to becoming ill, given the environment in which we find ourselves. Although having a relative with the illness increases a person’s risk of becoming ill, there is no single gene that causes schizophrenia. Instead, there are lots that, added together, increase the likelihood that a person will become ill. Many of the genetic differences that increase a person’s risk of developing schizophrenia are common in the general population. These differences consist of single “letter” changes in the DNA sequence that “tag” regions of the genome and, presumably, nearby genes, as being important in schizophrenia. Over 100 tags have now been linked to schizophrenia and it is likely that more remain to be discovered.'