"When one of these rare genetic variations is present in a person, the result is a moderate to large increase in disease risk. In a study lead by Dr. Michael O'Donovan from Cardiff University we also found other relatively frequent variations that slightly increase a person's risk. Our results could make a significant contribution to the further research concerning the causes of schizophrenia as well as the development of diagnostic tests-and possibly treatment," the researcher added.
The researcher points out that, contrary to common belief, a split personality is not one of the potential symptoms of schizophrenia.
"Persons affected with the illness, however, may exhibit changes in thought and behaviour. Hallucinations or delusions are only a few of the potential symptoms of this severe mental illness," says Dan Rujescu, adding that symptoms may also include a blunted affect along with episodes of depression.
Previous studies have shown that besides environmental factors, a person's genetics may also contribute to schizophrenia.
The hereditary pattern of the underlying genetic factors, however, proved extraordinarily complex and can be decoded only with great difficulty.
"There are presumably several genetic factors working together, each of which only has a very small effect on disease risk or which occur very rarely and have a moderate to strong effect," said Rujescu.
"For this reason, the field of schizophrenia genetics should be concerned with identifying these so-called risk genes. We have certainly made an important leap in the search for genetic factors. Yet there is not a single 'schizophrenia gene' but rather only genetic variations that can increase or decrease one's susceptibility to the illness," the researcher added.
Unlike previous studies that were only based on the genetic data of a relatively smaller number of persons, the newly published studies were based on the data of thousands of persons.
"Altogether, a great number of institutes took part in both studies," reports Rujescu.
"We would never have been able to achieve the enormous sample size otherwise and were therefore able to find associations between the genetic variations and the illness-without regional or national differences. What is also particularly interesting here is that there are clearly different mechanisms that come into play.
For example, we have found rare genetic variations that have a major influence, but we have also found frequent genetic variations that have only a minor effect on the disease risk," the researcher said.