Scientists have found that there is not a single type of schizophrenia, but that it consists of a group made up of eight genetically different types of diseases.
The research, from the universities of Granada (Spain) and Washington in St Louis (US), could be an important first step towards a better diagnosis and treatment of the disease, which affects approximately 1 per cent of world population.
Previous research has shown that approximately 80 per cent of the risk of suffering from schizophrenia was hereditary.
The new research has for the first time identified the different gene networks that contribute to the existence of eight different types of schizophrenia.
The study included 4,196 patients diagnosed with schizophrenia and 3,200 healthy patients participated as control group.
"What we did with this research, after a decade of frustration in the field of psychiatric genetics, is identify the manner in which the genes interact with each other, in an orchestrated manner in the case of healthy patients, or disorganised, as happens in the cases that lead to the different types of schizophrenia," said Igor Zwir, a researcher at the University of Granada and co-author of the study published in the American Journal of Psychiatry.
In some patients with hallucinations or delirium, for instance, researchers agree that there are different networks of genes related to their respective symptoms, which demonstrates that specific genetic variations interact with each other.
This genetic analysis leads to 95 per cent certainty in predicting the onset of schizophrenia.
In another group, they found that incongruent speech and disorganised behaviour are specifically associated with a DNA variations network that leads to a 100 per cent risk of suffering schizophrenia.
Researchers divided the patients according to the type and seriousness of positive symptoms (such as different types of hallucinations or deliriums), or negative symptoms (such as lack of initiative, troubles in organising thoughts, or lack of connection between emotion and thought).
In parallel, scientists classified the profiles of these symptoms into eight qualitative types of different diseases according to the underlying genetic conditions.
Although individual genes only present weak, inconsistent associations with schizophrenia, the interaction networks of gene groups pose a high risk of suffering from the disease, between 70 and 100 per cent, "which makes it almost impossible that individuals with those genetic variation networks will avoid schizophrenia," researchers said.
Researchers found a total of 42 genes groups that influenced in a variety of ways the risk of suffering schizophrenia.
