Schizophrenia is a complex mental disorder, characterised by wide variability, both in its causes and clinical presentation; it can lead to alterations in thought, perception, emotions and behaviour.
The risk factors involved in schizophrenia are diverse, but the genetic one is the most significant; it is estimated to account for 80% of disease cases. This increases the possibility of schizophrenia occurring in a family with a relative already diagnosed with this disease. In addition, the risk increases with increasing degree of kinship to the affected family member.
However, schizophrenia is not understood as a genetic disease; that is, one caused by a single gene. The influence of genetics in schizophrenia is very high, but this is not due to a single gene. The most current theories suggest the presence of various altered genes is required to develop the disease.
Environmental factors then come into play, including obstetric complications, drugs of abuse and certain viruses. In fact, the evidence shows that non-genetic risk factors not only contribute to the disease, but also help determine which groups of people are most at risk; this can improve prevention and early diagnosis of the disease. For example, schizophrenia has a greater preponderance in men, people in urban areas, cannabis users (marijuana or hashish) and immigrants.
Genetic inheritance, in combination with these environmental factors, predisposes a greater vulnerability to developing the disease, triggering the onset of symptoms.
To understand the causes and functioning of schizophrenia better, the contribution of these environmental factors needs to be explored in more detail. A study published in the journal, Schizophrenia Research, suggests that part of the answer lies in epigenetics, which are changes that turn genes on or off without changing the DNA sequence, due to exposure to environmental factors, among others. These epigenetic analyses are increasingly applied in research related to drug response in the field of psychiatry. They can be combined with genetic information to provide a more complete antipsychotic response prediction.
Apart from risk factors, the most frequent causes of schizophrenia are biochemical alterations, such as communication problems between neurons; alterations in the structure of the brain, such as a smaller volume of certain areas or even in the size of the brain; and disturbances in brain function, such as decreased function of the prefrontal cortex, which is involved in the ability to reason.
Thus, it is clear that studying the different causes and risk factors that influence the appearance of schizophrenia will contribute to improving the treatment and prevention of a disease that, today, is still quite unknown.