Previously doctors had assumed that the two conditions were quite separate. But new research shows for the first time that both have a common genetic basis that leads people to develop one or other of the two illnesses.
Three different international studies investigated the genetic basis of schizophrenia by pooling their analysis of about 15,000 patients and nearly 50,000 healthy subjects to find that thousands of tiny genetic mutations – known as single nucleotide polymorphisms (SNPs) – are operating in raising the risk of developing the illness.
Although the schizophrenia studies have so far only identified a handful of the many thousands of genetic variations implicated in the mental illness, scientists believe it represents a breakthrough that will accelerate the understanding of the condition and the development of new drugs and treatments. “This is a pretty major breakthrough for us because before today you could count on the thumb of one hand the number of common [genetic] variants that have been reliably identified for schizophrenia,” said Michael O’Donovan, professor of psychiatric genetics at the Medical Research Council’s neurogenetics centre in Cardiff.
“However, what we’ve found so far explains only a tiny fraction of the total risk of schizophrenia. Some of us were surprised to find that not only did these genes contribute to schizophrenia but they also contribute to bipolar disorder. So that really suggests that the two disorders are not really as distinct as we thought in psychiatry.”