To our knowledge, this is the first report for a Latin American population. The joint influence of these genes on depression has been frequently examined in regards to a heterogeneous set of “environmental” disadvantageous variables, including maltreatment in childhood (Kaufman et al. 2006), “risky families” (Carver

et al. 2011), CAs (Wichers et al. 2008; Aguilera Inhibitors,research,lifescience,medical et al. 2009; Grabe et al. 2012), pre/peri gestational difficulties, and family and stressful events during childhood (Nederhof et al. 2010), or threatening events during the last year in the elderly (Kim et al. 2007). We found as expected, a strong association between most of the CAs studied and the manifestation of clinical depression, either if they were analyzed as independent variables or included as adversity factors. Moreover, there was a clear-cut effect of the cumulative number of CAs on the increase in the prevalence of major depression. On the other hand, when genetic data were analyzed independently of CAs, SLC6A4 (SS Inhibitors,research,lifescience,medical genotype) but not BDNF showed a marginal but statistically significant association with the disorder. It is worth noting that the frequently cited drawback of the probability of spurious positive or negative results of case–control

genetic association studies as result of population stratification bias was reduced as both groups of comparison were drawn from the same set of individuals. Inhibitors,research,lifescience,medical Moreover, cases as well as controls were part of a single admixed population as indicated by the analysis of ancestry markers. The absence of a main genetic effect for BDNF was not unexpected; for example, genetic association studies Inhibitors,research,lifescience,medical see more related to BDNF Val66Met and mood disorders have frequently produced mixed or negative results as have been showed in two recent meta-analyses (Gratacòs et al. 2007; Verhagen et al. 2010). Moreover, a previous meta-analysis did not detect a significant association between the short allele of the 44-bp SLC6A4 insertion/deletion polymorphism and unipolar depression

(Lasky-Su et al. 2005). Remarkably, Inhibitors,research,lifescience,medical a “refractory” or resilient phenotype to the mounting influence of CAs in those adolescents bearing the Met 66 allele was noted, which emphasizes the importance of including “environmental and genetic data” in the identification of liability or resilience phenotypes. The “protective” effect why of the BDNF Met allele was in the opposite direction to our initial hypothesis, which was based upon experimental observations in humans indicating striking brain anatomical and functional differences among genotypes. For example, as compared with those Val/Val subjects, Met allele carriers showed a reduced hippocampal gray matter volume (Pezawas et al. 2004; Szeszko et al. 2005; Bueller et al. 2006), a less efficient verbal episodic memory, and an abnormal hippocampal activation on performing a working memory task response (Egan et al.