The stress hormone-regulating hypothalamic-pituitary-adrenal (HPA) axis has been implicated in the causality as well as the treatment of depression. To investigate a possible association between genes regulating the HPA axis and response to antidepressants and susceptibility for depression, we genotyped single-nucleotide polymorphisms in eight of these genes in depressed individuals and matched controls. We found significant associations of response to antidepressants and the recurrence of depressive episodes with single-nucleotide polymorphisms in FKBP5, a glucocorticoid receptor-regulating cochaperone of hsp-90, in two independent samples. These single-nucleotide polymorphisms were also associated with increased intracellular FKBP5 protein expression, which triggers adaptive changes in glucocorticoid receptor and, thereby, HPA-axis regulation. Individuals carrying the associated genotypes had less HPA-axis hyperactivity during the depressive episode. We propose that the FKBP5 variant-dependent alterations in HPA-axis regulation could be related to the faster response to antidepressant drug treatment and the increased recurrence of depressive episodes observed in this subgroup of depressed individuals. These findings support a central role of genes regulating the HPA axis in the causality of depression and the mechanism of action of antidepressant drugs.

Liability to alcohol dependence (AD) is heritable, but little is known about its complex polygenic architecture or its genetic relationship with other disorders. To discover loci associated with AD and characterize the relationship between AD and other psychiatric and behavioral outcomes, we carried out the largest GWAS to date of DSM-IV diagnosed AD. Genome-wide data on 14,904 individuals with AD and 37,944 controls from 28 case/control and family-based studies were meta-analyzed, stratified by genetic ancestry (European, N = 46,568; African; N = 6,280). Independent, genome-wide significant effects of different ADH1B variants were identified in European (rs1229984; p = 9.8E-13) and African ancestries (rs2066702; p = 2.2E-9). Significant genetic correlations were observed with 17 phenotypes, including schizophrenia, ADHD, depression, and use of cigarettes and cannabis. The genetic underpinnings of AD only partially overlap with those for alcohol consumption, underscoring the genetic distinction between pathological and non-pathological drinking behaviors.

We report a GWAS of alcohol dependence (AD) in European-American (EA) and African-American (AA) populations, with replication in independent samples of EAs, AAs and Germans. Our sample for discovery and replication was 16 087 subjects, the largest sample for AD GWAS to date. Numerous genome-wide significant (GWS) associations were identified, many novel. Most associations were population specific, but in several cases were GWS in EAs and AAs for different SNPs at the same locus, showing biological convergence across populations. We confirmed well-known risk loci mapped to alcohol-metabolizing enzyme genes, notably ADH1B (EAs: Arg48His, P = 1.17 × 10−31; AAs: Arg369Cys, P = 6.33 × 10−17) and ADH1C in AAs (Thr151Thr, P = 4.94 × 10−10), and identified novel risk loci mapping to the ADH gene cluster on chromosome 4 and extending centromerically beyond it to include GWS associations at LOC100507053 in AAs (P = 2.63 × 10−11), PDLIM5 in EAs (P = 2.01 × 10−8), and METAP in AAs (P = 3.35 × 10−8). We also identified a novel GWS association (1.17 × 10−10) mapped to chromosome 2 at rs1437396, between MTIF2 and CCDC88A, across all of the EA and AA cohorts, with supportive gene expression evidence, and population-specific GWS for markers on chromosomes 5, 9 and 19. Several of the novel associations implicate direct involvement of, or interaction with, genes previously identified as schizophrenia risk loci. Confirmation of known AD risk loci supports the overall validity of the study; the novel loci are worthy of genetic and biological follow-up. The findings support a convergence of risk genes (but not necessarily risk alleles) between populations, and, to a lesser extent, between psychiatric traits.

Context Identification of genes contributing to alcohol dependence will improve our understanding of the mechanisms underlying this disorder. Objective To identify susceptibility genes for alcohol dependence through a genome-wide association study (GWAS) and follow-up study in a population of German male inpatients with an early age at onset. Design The GWAS included 487 male inpatients with DSM-IV alcohol dependence with an age at onset below 28 years and 1,358 population based control individuals. The follow-up study included 1,024 male inpatients and 996 age-matched male controls. All subjects were of German descent. The GWAS tested 524,396 single nucleotide polymorphisms (SNPs). All SNPs with p<10-4 were subjected to the follow-up study. In addition, nominally significant SNPs from those genes that had also shown expression changes in rat brains after chronic alcohol consumption were selected for the follow-up step. Results The GWAS produced 121 SNPs with nominal p<10-4. These, together with 19 additional SNPs from homologs of rat genes showing differential expression, were genotyped in the follow-up sample. Fifteen SNPs showed significant association with the same allele as in the GWAS. In the combined analysis, two closely linked intergenic SNPs met genome-wide significance (rs7590720 p=9.72×10-9; rs1344694 p=1.69×10-8). They are located on chromosome 2q35, a region which has been implicated in linkage studies for alcohol phenotypes. Nine SNPs were located in genes, including CDH13 and ADH1C genes which have been reported to be associated with alcohol dependence. Conclusion This is the first GWAS and follow-up study to identify a genome-wide significant association in alcohol dependence. Further independent studies are required to confirm these findings.

Context: Brain-derived neurotrophic factor (BDNF) modulates hippocampal plasticity, which is believed to be altered in patients with major depression.Objective: To examine the effect of the BDNF Val66Met polymorphism on hippocampal and amygdala volumes in patients with major depression and in healthy control subjects.Design: Cross-sectional comparison between patients and controls.Setting: Inpatients with major depression from the Department of Psychiatry and Psychotherapy and healthy controls from the community were recruited. Participants:The study population of 120 subjects included 60 patients with major depression and 60 healthy controls. Main Outcome Measures:Using a combined strategy, hippocampal and amygdala volumes were estimated on high-resolution magnetic resonance images, and genotyping was performed for the BDNF Val66Met polymorphism.Results: Patients had significantly smaller hippocampal volumes compared with controls (P = .02). Significantly smaller hippocampal volumes were observed for patients and for controls carrying the Met-BDNF allele compared with subjects homozygous for the Val-BDNF allele (P=.006). With respect to amygdala volumes, no significant differences between patients and controls and no significant main effects for the BDNF Val66Met polymorphism were observed.Conclusions: These genotype-related alterations suggest that Met-BDNF allele carriers might be at risk to develop smaller hippocampal volumes and may be susceptible to major depression. This study supports findings from animal studies that the hippocampus is involved in brain development and plasticity. Psychiatry. 2007;64:410-416 Arch Gen

Tryptophan hydroxylase (TPH), being the rate-limiting enzyme in the biosynthesis of serotonin plays a major role as candidate gene in several psychiatric disorders. Recently, a second TPH isoform (TPH2) was identified in mice, which was exclusively present in the brain. In a previous post-mortem study of our own group, we could demonstrate that TPH2 is also expressed in the human brain, but not in peripheral tissues. This is the first report of an association study between polymorphisms in the TPH2 gene and major depression (MD). We performed singlenucleotide polymorphism (SNP), haplotype and linkage disequlibrium studies on 300 depressed patients and 265 healthy controls with 10 SNPs in the TPH2 gene. Significant association was detected between one SNP (P ¼ 0.0012, global P ¼ 0.0051) and MD. Haplotype analysis produced additional support for association (Po0.0001, global P ¼ 0.0001). Our findings provide evidence for an involvement of genetic variants of the TPH2 gene in the pathogenesis of MD and might be a hint on the repeatedly discussed duality of the serotonergic system. These results may open up new research strategies for the analysis of the observed disturbances in the serotonergic system in patients suffering from several other psychiatric disorders.

The concept that genetic factors contribute to the complex trait of suicidal behaviour has stimulated much work aimed at identifying susceptibility genes. So far molecular genetic studies focused on the serotonergic pathway as the intent to die and the lethality of suicide acts were related to the serotonergic system. Two genes have so far emerged as being involved in the vulnerability for suicidality: first, the intronic polymorphisms (A218C or A779C) of the tryptophan hydroxylase 1 (TPH1) gene, which was suggested as a quantitative risk factor for suicidal behaviour; second, the insertion/deletion polymorphism of the serotonin transporter gene (5-HTTLPR), which does not seem to be involved in general suicidal behaviour, but in violent and repeated suicide attempts. The data have further shown that the MAOA gene, which is consistently associated with impulsive-aggressive personality traits, is not related to suicide but might induce violent methods in subjects with other suicide risk factors. Predominantly negative were the findings with any type of the serotonin receptors and inconsistent with catecholamine-synthesizing and -metabolizing enzymes or with the dopaminergic receptors. This paper reviews the status of current knowledge in this area, points to the weakness of the investigations and presents new approaches beyond the serotonergic system.

Alcohol dependence (AD) is an important contributory factor to the global burden of disease. The etiology of AD involves both environmental and genetic factors, and the disorder has a heritability of around 50%. The aim of the present study was to identify susceptibility genes for AD by performing a genome-wide association study (GWAS). The sample comprised 1,333 male in-patients with severe DSM-IV AD and 2,168 controls. These included 487 patients and 1,358 controls from a previous GWAS study by our group. All individuals were of German descent. Single marker tests and a polygenic score based analysis to assess the combined contribution of multiple markers with small effects were performed. The SNP rs1789891, which is located between the ADH1B and ADH1C genes, achieved genome-wide significance (p=1.27E–8; OR=1.46). Other markers from this region were also associated with AD, and conditional analyses indicated that these made a partially independent contribution. The SNP rs1789891 is in complete linkage disequilibrium with the functional Arg272Gln variant (p=1.24E–7, OR=1.31) of the ADH1C gene, which has been reported to modify the rate of ethanol oxidation to acetaldehyde in vitro. A polygenic score based approach produced a significant result (p=9.66E–9). This is the first GWAS of AD to provide genome-wide significant support for the role of the ADH gene cluster and to suggest a polygenic component to the etiology of AD. The latter result suggests that many more AD susceptibility genes still await identification.