There is no single gene for schizophrenia, scientists say. But there are eight combinations of genes that are responsible for the development of different types of this disease.
In a person with a schizophrenic disorder, thinking becomes illogical: ideas are connected to each other remotely or without an obvious pattern. Often there are hallucinations accompanied by imaginary sensations – sights, smells or sounds (voices) that are taken for real.
Speech can become incoherent – turn into a “verbal crumble” of logically incoherent or invented words. Emotions can fade away and not appear outwardly in any way or be inappropriate in the current situation. Schizophrenia occurs in 1% of people living on earth1. The risk of inheriting schizophrenia is approximately 80%.
Studying the issue
Even after many years of research, scientists have not been able to find the gene responsible for causing schizophrenia. Today, researchers are inclined to believe that there are not one gene, but eight different combinations of genes that contribute to the development of eight types of schizophrenia.
That is, schizophrenia is not a single disease, but a group of eight genetically distinct types of disease, each of which has its own set of symptoms.
“In the past, scientists have looked for a link between a single gene and schizophrenia,” explains Dragan Svrakic, MD and professor of psychiatry at the University of Washington (USA). “When one study linked a gene to a disease, another study did not. It is only now that the idea has emerged that genes interact with each other, rather than acting on their own.”
Confirmation of data
4196 patients with a diagnosis of schizophrenia and 3200 adults without this diagnosis took part in the large-scale studies conducted. The scientists compared different DNA variations in all participants.
In total, scientists analyzed about 700 regions within the genome where one DNA element was changed. In this way, the researchers tried to discover which genetic variations cause the disease.
So, for example, hallucinations and delusions were associated with one set of genes, which showed the likelihood of developing schizophrenia in 95% of cases. Other features (disorganized speech and behavior) were found with a different set of DNA causing a 100% chance of schizophrenia.
Scientists could draw such conclusions only by dividing patients into groups according to genetic variations and symptoms. This helped them see that different kinds of genes worked together to cause the symptoms of the disease.2.
“Genes don’t work on their own. They prefer to interact with each other in the manner of an orchestra, says Dr. Robert Cloninger, one of the authors of the study. “And in order to understand how they work, you need to know not only each member of the “orchestra”, but also what kind of relationship they are in.”3.
The discovery made will help scientists more effectively help treat the disease – or rather, each of its individual types. In addition, studying the interaction of genes can help in the treatment of other, non-psychiatric diseases: for example, hypertension and diabetes.
1 According to the American Psychiatric Association: “Schizophrenia”, American Psychiatric Association.
2 J. Dryden «Schizophrenia not a single disease but multiple genetically distinct disorders», Washington University in St. Louis, September 2014.
2 «Schizophrenia has eight avatars, not one», Zee News, February 2015.