Identifying genetic variants influencing human brain structures may reveal new biological mechanisms underlying cognition and neuropsychiatric illness. The volume of the hippocampus is a biomarker of incipient Alzheimer’s disease1,2 and is reduced in schizophrenia3, major depression4 and mesial temporal lobe epilepsy5. Whereas many brain imaging phenotypes are highly heritable6,7, identifying and replicating genetic influences has been difficult, as small effects and the high costs of magnetic resonance imaging (MRI) have led to underpowered studies. Here we report genome-wide association meta-analyses and replication for mean bilateral hippocampal, total brain and intracranial volumes from a large multinational consortium. The intergenic variant rs7294919 was associated with hippocampal volume (12q24.22; N = 21,151; P = 6.70 × 10−16) and the expression levels of the positional candidate gene TESC in brain tissue. Additionally, rs10784502, located within HMGA2, was associated with intracranial volume (12q14.3; N = 15,782; P = 1.12 × 10−12). We also identified a suggestive association with total brain volume at rs10494373 within DDR2 (1q23.3; N = 6,500; P = 5.81 × 10−7).

The Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Consortium is a collaborative network of researchers working together on a range of large-scale studies that integrate data from 70 institutions worldwide. Organized into Working Groups that tackle questions in neuroscience, genetics, and medicine, ENIGMA studies have analyzed neuroimaging data from over 12,826 subjects. In addition, data from 12,171 individuals were provided by the CHARGE consortium for replication of findings, in a total of 24,997 subjects. By meta-analyzing results from many sites, ENIGMA has detected factors that affect the brain that no individual site could detect on its own, and that require larger numbers of subjects than any individual neuroimaging study has currently collected. ENIGMA’s first project was a genome-wide association study identifying common variants in the genome associated with hippocampal volume or intracranial volume. Continuing work is exploring genetic associations with subcortical volumes (ENIGMA2) and white matter microstructure (ENIGMA-DTI). Working groups also focus on understanding how schizophrenia, bipolar illness, major depression and attention deficit/hyperactivity disorder (ADHD) affect the brain. We review the current progress of the ENIGMA Consortium, along with challenges and unexpected discoveries made on the way.

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Childhood maltreatment and depressive disorders have both been associated with a dysregulation of the hypothalamic-pituitary-adrenal axis. The FKBP5 gene codes for a co-chaperone regulating the glucocorticoid-receptor sensitivity. Previous evidence suggests that subjects carrying the TT genotype of the FKBP5 gene single-nucleotide polymorphism (SNP) rs1360780 have an increased susceptibility to adverse effects of experimental stress. We therefore tested the hypothesis of an interaction of childhood abuse with rs1360780 in predicting adult depression. In all, 2157 Caucasian subjects from the Study of Health in Pomerania (German general population) completed the Beck Depression Inventory (BDI-II) and Childhood Trauma Questionnaire. The DSM-IV diagnosis of major depressive disorder (MDD) was assessed by interview. Genotypes of rs1360780 were taken from the Affymetrix Human SNP Array 6.0. Significant interaction (p ¼ 0.006) of physical abuse with the TT genotype of rs1360780 was found increasing the BDI-II score to 17.4 (95% confidence interval (CI) ¼ 12.0-22.9) compared with 10.0 (8.2-11.7) in exposed CC/CT carriers. Likewise, the adjusted odds ratio for MDD in exposed TT carriers was 8.2 (95% CI ¼ 1.9-35.0) compared with 1.3 (0.8-2.3) in exposed subjects with CC/CT genotypes. Relative excess risk due to interaction (RERI) analyses confirmed a significant additive interaction effect (RERI ¼ 6.8; po0.05). In explorative analyses, the most severe degree of sexual and emotional abuse also yielded significant interaction effects (po0.05). This study revealed interactions between physical abuse and rs1360780 of the FKBP5 gene, confirming its role in the individual susceptibility to depression. Given the large effect sizes, rs1360780 could be included into prediction models for depression in individuals exposed to childhood abuse.

Extraversion is a relatively stable and heritable personality trait associated with numerous psychosocial, lifestyle and health outcomes. Despite its substantial heritability, no genetic variants have been detected in previous genome-wide association (GWA) studies, which may be due to relatively small sample sizes of those studies. Here, we report on a large meta-analysis of GWA studies for extraversion in 63,030 subjects in 29 cohorts. Extraversion data came from multiple personality inventories; extraversion scores were harmonized across cohorts and included as the phenotype in the GWA meta-analysis. No genome-wide significant associations were found at the single nucleotide polymorphism (SNP) level but there was one significant hit at the gene level for a long non-coding RNA site (LOC101928162). Genome-wide complex trait analysis in two large cohorts showed that the additive variance explained by common SNPs was not significantly different from zero, but polygenic risk scores, weighted using linkage information, significantly predicted extraversion scores in an independent cohort. These results show that extraversion is a highly polygenic personality trait, with gene action different from other complex behavioral traits. Future studies are required to further determine which genetic variants, by what modes of gene action, constitute the heritable nature of extraversion.

Our results substantiate evidence that diagnosed untreated hypothyroidism is associated with depression and anxiety, and that diagnosed untreated hyperthyroidism is associated with depression.

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Dysregulations of the hypothalamic-pituitary-adrenal (HPA) axis have been implicated in the pathogenesis of depressive disorders and the corticotropin-releasing hormone (CRH) was found to modulate emotional memory consolidation. Recently, two studies have reported an interaction between childhood abuse and the TAT-haplotype of the CRH-Receptor Gene (CRHR1) connecting childhood adversities and genetic susceptibility to adult depression. We tested the hypothesis of an interaction of childhood maltreatment with single nucleotide polymorphisms (SNPs) and haplotypes of the CRHR1 gene not previously investigated. Caucasian subjects (n = 1,638) from the German general population (Study of Health in Pomerania, SHIP) were analyzed. As in the previous studies, childhood abuse and neglect were assessed with the Childhood Trauma Questionnaire (CTQ) and depression with the Beck Depression Inventory (BDI-2). The CRHR1-SNPs were genotyped on the Affymetrix Genome-Wide Human SNP Array 6.0 platform. We identified an interaction between the TAT-haplotype and childhood physical neglect. The interaction with physical neglect showed significant (P < 0.05) results in 23 of the 28 SNPs, with rs17689882 (P = 0.0013) reaching "gene-wide" significance. Although we did not replicate the specific interaction of abuse and the TAT-haplotype of the CRHR1 gene we confirmed the relevance of an interplay between variants within the CRHR1 gene and childhood adversities in the modulation of depression in adults. The largest effect was found for rs17689882, a SNP previously not analyzed. Relevant sample differences between this and prior studies like lower BDI-2 scores, less childhood maltreatment and higher psychosocial functioning may account for the differences in gene-environment interaction findings. © 2010 Wiley-Liss, Inc.