[Show abstract][Hide abstract] ABSTRACT: Evidence of marked variability in response among people exposed to the same environmental risk implies that individual differences in genetic susceptibility might be at work. The study of such Gene-by-Environment (GxE) interactions has gained momentum. In this article, the authors review research about one of the most extensive areas of inquiry: variation in the promoter region of the serotonin transporter gene (SLC6A4; also known as 5-HTT) and its contribution to stress sensitivity. Research in this area has both advanced basic science and generated broader lessons for studying complex diseases and traits. The authors evaluate four lines of evidence about the 5-HTT stress-sensitivity hypothesis: 1) observational studies about the serotonin transporter linked polymorphic region (5-HTTLPR), stress sensitivity, and depression in humans; 2) experimental neuroscience studies about the 5-HTTLPR and biological phenotypes relevant to the human stress response; 3) studies of 5-HTT variation and stress sensitivity in nonhuman primates; and 4) studies of stress sensitivity and genetically engineered 5-HTT mutations in rodents. The authors then dispel some misconceptions and offer recommendations for GxE research. The authors discuss how GxE interaction hypotheses can be tested with large and small samples, how GxE research can be carried out before as well as after replicated gene discovery, the uses of GxE research as a tool for gene discovery, the importance of construct validation in evaluating GxE research, and the contribution of GxE research to the public understanding of genetic science.
American Journal of Psychiatry 03/2010; 167(5):509-27. DOI:10.1176/appi.ajp.2010.09101452 · 13.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Human observational studies have shown that, in interaction with life stress, the short or S-allele of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) is associated with an enhanced risk for depression. However, this gene-by-environment interaction (G×E) has recently been questioned by two meta-analyses. We aim to provide an overview and appraisal of recent developments and controversies.
The statistical approach of the meta-analyses aimed at a very strict replication of the initial finding and, accordingly, included only a minority of all available studies. Furthermore, the negative results of the meta-analyses appear to be predominantly driven by a few large studies that used retrospective, self-report measures of life stress. In contrast, among 19 studies using interview-based or more objective measures of stress, there were 13 replications, five part-replications and only one nonreplication. Finally, a broader approach based on evidence from different research fields and methodologies supports a 5-HTTLPR by stress interaction.
Whereas there is no doubt that the meta-analyses are methodologically sound, it appears that this technique is only in part suitable for appraising all of the available evidence. Furthermore, convergent evidence is accumulating from different research fields that 5-HTTLPR is indeed closely associated with different biological pathways associated with stress regulation and depression.
Current opinion in psychiatry 11/2010; 23(6):582-7. DOI:10.1097/YCO.0b013e32833f0e3a · 3.55 Impact Factor
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