The complex etiology of schizophrenia - general state of the art.

The etiology of schizophrenia is complex. The aim of this article is to present a global view of the causes of schizophrenia and their interconnectivity. Recent genetic research into schizophrenia is based on genome-wide association studies, the assessment of DNA copy number variations, and the concept of endophenotypes. A lot of suspected genes have already been identified, mostly relating to neurodevelopment, neuroplasticity, immunology and neuroendocrinology. Gene-environment interactions (G×E) reflect genetic variation in susceptibility to the environment. Psychosocial stress and cannabis abuse seem to be the most important environmental factors in schizophrenia etiology. Epigenetic mechanisms, particularly DNA methylation, histone modifications, and non-coding RNAs are the most important linking factor among the genetic and prenatal environmental variables in the etiology of schizophrenia. Postnatal risk factors (e.g., stress, urbanicity, cannabis use) may also affect the risk of schizophrenia via the potentiation of vulnerable brain pathways. Many questionable issues pertaining to G×E assessment of schizophrenia still persist and relate to the exact assessment of environmental agents as well as psychopathology. In future research concerning G×E in schizophrenia, the study samples should be adequately large, schizophrenia endophenotypes should be involved, prospective studies should be supported, environmental causative factors as well as psychopathology should be assessed in a quantitative way, the multiple interactions among the variety of environmental and genetic variables should be evaluated, and epigenetic factors should not be neglected. The EU-GEI project of the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (2010-2015) may become a milestone in the schizophrenia G×E research.