Population stratification in European South-American subjects and its importance to psychiatric genetics research in Brazil.

Preliminary evidence of association between EFHC2, a gene implicated in fear recognition, and harm avoidance. Estratificação populacional em sul-americanos de origem européia e sua importância para a pesquisa genética psiquiátrica no Brasil (5-HTTLPR) and personality traits in asymptomatic patients with panic disorder.Segal S. Novel allelic variants in the human serotonin transporter gene linked polymorphism (5-HTTLPR) among depressed patients with suicide attempt. Association between suicide attempts in south Brazilian depressed patients with the serotonin transporter polymorphism. Dear Editors, It is really very exciting to know that another Brazilian group is working with molecular investigation in the field of psychiatric genetics. 1 When we decided to write a paper about the particularities, advantages and difficulties of conducting psychiatric genetic studies in the Brazilian population, we were aware of the possible biases of a narrative review. 2 However, that kind of approach seemed to be a more appropriate method in terms of our proposal because we believe that, by describing the history, development, and management of psychiatric genetic investigations in Brazil, we would be contemplating several contextual, cultural and political aspects and integrating different and independent fields of research in order to acquire a wider and multidisciplinary view of the subject at hand. There is also another important point raised by Salum et al. 1 that needs to be addressed. Differently from what they claim, the use of " more homogenous samples like the Caucasians " does not " avoid stratification " in association studies on complex disorders such as neuropsychiatric disorders. 2 Nowadays, it is well known that even when studying samples from a specific continental population such as the European, ethnic stratification can produce false associations at markers whose frequency differs across subpopulations. 3 For example, in a recent whole genome association study of rheumatoid arthritis in European Americans, markers in the LCT and IRF4 genes could have been falsely implicated as being associated with the disease had no control method been applied to for the population's