[Contemporary GWAS studies of depression: the critical role of phenotyping]

The need to use large samples to identify the genetic risk loci of mental disorders has led us to the dilemma of phenotyping quality. Especially this problem relates to such common mental disorders as depression (lifetime prevalence 16.2%). On the one hand, there is a very resource-intensive method of capturing patient data by physicians using diagnostic criteria of mental disorders (DSM-V/ICD-10). On the other, there is a popular method of minimal phenotyping using hospital registers, self-reports of respondents on symptoms, diagnosis and treatment of depression. To date, there is no ideal method for phenotyping depression because all of them focus only on its clinical symptoms. The active usage of minimal phenotyping in Genome-Wide Association Study (GWAS) has led to a significant increase in both clinical and genetic heterogeneity of depression. However, an important limitation of using DSM-V/ICD-10 is the high cost of phenotyping due to the involvement of medical specialists. Thus, the most rational is to use electronic diagnostic questionnaires based on DSM-V/ICD-10 criteria. Such an approach will accelerate the increase in research capacity, but will preserve all internal contradictions inherent in official diagnostic classifications (heterogeneity of phenotypes, absence of objective diagnostic criteria, categorical approach, etc.). In this regard, the critical role of psychiatric epidemiology is growing both in the development of standardized tools for operationalized diagnostic criteria and in future GWAS by introducing new phenotypic subtypes of depression and its dimensions.