Objective. The paper presents the concept of endophenotype in psychiatry as exemplified by schizophrenia.
Review. In genetic research on mental disorders a concept of endophenotypes or "indirect phenotypes " has been introduced. This "indirect" diagnostic approach can be used in cases not fulfilling all the clinical diagnostic criteria for a specific mental disorder. Such persons might be carriers of a relevant gene manifested in the form of an endophenotype. In the concept of endophenotypes foundations of a biological classification of mental disorders are taken into account. In molecular and genetic studies on schizophrenia the following endophenotypes are analyzed: neurophysiologic, neurocognitive, neuropsychological, neuroanatomical, biochemical, and behavioral. The most popular among researchers are neurophysiologic and neuropsychological parameters known as phenotypic markers of schizophrenia.
Conclusions. Research findings obtained so far corroborate the usefulness of endophenotypes in further genetic research. Identification of more homogeneous phenotypes of mental illness will allow to develop new etiological models of schizophrenia contributing to our better understanding of molecular underpinnings of mental disorders. Furthermore, implementation of endophenotype research findings in clinical practice might help to reduce variability of patient subgroups on the grounds of similarities in their pathophysiological features, symptoms and functional deficits. This might facilitate further research into novel, more effective treatment approaches.