The role of genetic variation in the causation of mental illness: an evolution-informed framework

Asian-European differentiation of schizophrenia-associated genes driven by admixture and natural selection

The European-centered genome-wide association studies of schizophrenia (SCZ) may not be well applied to non-European populations. We analyzed 1,592 reported SCZ-associated genes using the public genome data and found an overall higher Asian-European differentiation on the SCZ-associated variants than at the genome-wide level. Notable examples included 15 missense variants, a regulatory variant SLC5A10-rs1624825, and a damaging variant TSPAN18-rs1001292. Independent local adaptations in recent 25,000 years, after the Asian-European divergence, could have contributed to such genetic differentiation, as were identified at a missense mutation LTN1-rs57646126-A in Asians, and a non-risk allele ZSWIM6-rs72761442-G in Europeans. Altai-Neanderthal-derived alleles may have opposite effects on SCZ susceptibility between ancestries. Furthermore, adaptive introgression was detected on the non-risk haplotype at 1q21.2 in Europeans, while in Asians it was observed on the SCZ risk haplotype at 3p21.31 which is also potentially ultra-violet protective. This study emphasizes the importance of including more representative Asian samples in future SCZ studies.

Identification of novel rare variants for anxiety: an exome-wide association study in the UK Biobank

BACKGROUND

Rare variants are believed to play a substantial role in the genetic architecture of mental disorders, particularly in coding regions. However, limited evidence supports the impact of rare variants on anxiety.

METHODS

Using whole-exome sequencing data from 200,643 participants in the UK Biobank, we investigated the contribution of rare variants to anxiety. Firstly, we computed genetic risk score (GRS) of anxiety utilizing genotype data and summary data from a genome-wide association study (GWAS) on anxiety disorder. Subsequently, we identified individuals within the lowest 50% GRS, a subgroup more likely to carry pathogenic rare variants. Within this subgroup, we classified individuals with the highest 10% 7-item Generalized Anxiety Disorder scale (GAD-7) score as cases (N = 1869), and those with the lowest 10% GAD-7 score were designated as controls (N = 1869). Finally, we conducted gene-based burden tests and single-variant association analyses to assess the relationship between rare variants and anxiety.

RESULTS

Totally, 47,800 variants with MAF ≤0.01 were annotated as non-benign coding variants, consisting of 42,698 nonsynonymous SNVs, 489 nonframeshift substitution, 236 frameshift substitution, 617 stop-gain and 40 stop-loss variants. After variation aggregation, 5066 genes were included in gene-based association analysis. Totally, 11 candidate genes were detected in burden test, such as RNF123 (PBonferroni adjusted = 3.40 × 10-6), MOAP1(PBonferroni adjusted = 4.35 × 10-4), CCDC110 (PBonferroni adjusted = 5.83 × 10-4). Single-variant test detected 9 rare variants, such as rs35726701(RNF123)(PBonferroni adjusted = 3.16 × 10-10) and rs16942615(CAMTA2) (PBonferroni adjusted = 4.04 × 10-4). Notably, RNF123, CCDC110, DNAH2, and CSKMT gene were identified in both tests.

CONCLUSIONS

Our study identified novel candidate genes for anxiety in protein-coding regions, revealing the contribution of rare variants to anxiety.

Co-fractionation-mass spectrometry to characterize native mitochondrial protein assemblies in mammalian neurons and brain

Human mitochondrial (mt) protein assemblies are vital for neuronal and brain function, and their alteration contributes to many human disorders, e.g., neurodegenerative diseases resulting from abnormal protein-protein interactions (PPIs). Knowledge of the composition of mt protein complexes is, however, still limited. Affinity purification mass spectrometry (MS) and proximity-dependent biotinylation MS have defined protein partners of some mt proteins, but are too technically challenging and laborious to be practical for analyzing large numbers of samples at the proteome level, e.g., for the study of neuronal or brain-specific mt assemblies, as well as altered mtPPIs on a proteome-wide scale for a disease of interest in brain regions, disease tissues or neurons derived from patients. To address this challenge, we adapted a co-fractionation-MS platform to survey native mt assemblies in adult mouse brain and in human NTERA-2 embryonal carcinoma stem cells or differentiated neuronal-like cells. The workflow consists of orthogonal separations of mt extracts isolated from chemically cross-linked samples to stabilize PPIs, data-dependent acquisition MS to identify co-eluted mt protein profiles from collected fractions and a computational scoring pipeline to predict mtPPIs, followed by network partitioning to define complexes linked to mt functions as well as those essential for neuronal and brain physiological homeostasis. We developed an R/CRAN software package, Macromolecular Assemblies from Co-elution Profiles for automated scoring of co-fractionation-MS data to define complexes from mtPPI networks. Presently, the co-fractionation-MS procedure takes 1.5-3.5 d of proteomic sample preparation, 31 d of MS data acquisition and 8.5 d of data analyses to produce meaningful biological insights.

Sex differences across developmental domains among children with a familial risk of severe mental disorders

BACKGROUND

Sex differences in brain structure and neurodevelopment occur in non-clinical populations. We investigated whether sex had a similar effect on developmental domains amongst boys and girls with a familial risk of schizophrenia (FHR-SZ), bipolar disorder (FHR-BP), and controls.

METHODS

Through Danish registries, we identified 522 7-year-old children (242 girls) with FHR-SZ, FHR-BP, and controls. We assessed their performance within the domains of neurocognition, motor function, language, social cognition, social behavior, psychopathology, and home environment.

RESULTS

FHR-SZ boys compared with FHR-SZ girls had a higher proportion of disruptive behavior and attention-deficit hyperactivity disorder (ADHD) and exhibited lower performance in manual dexterity, balance, and emotion recognition. No sex differences were found between boys and girls within FHR-BP group. Compared with controls, both FHR-SZ boys and FHR-SZ girls showed impaired processing speed and working memory, had lower levels of global functioning, and were more likely to live in an inadequate home environment. Compared with control boys, FHR-SZ boys showed impaired manual dexterity, social behavior, and social responsiveness, and had a higher proportion of ADHD and disruptive behavior disorder diagnoses. Stress and adjustment disorders were more common in FHR-BP boys compared with control boys. We found no differences between FHR-BP girls and control girls.

CONCLUSIONS

Impairment within neurodevelopmental domains associated within FHR-SZ boys v. FHR-SZ girls was most evident among boys, whereas no sex differences were found within the FHR-BP group (FHR-BP boys v. FHR-BP girls). FHR-SZ boys exhibited the highest proportion of early developmental impairments.

The contribution of Neanderthal introgression and natural selection to neurodegenerative diseases

Humans are thought to be more susceptible to neurodegeneration than equivalently-aged primates. It is not known whether this vulnerability is specific to anatomically-modern humans or shared with other hominids. The contribution of introgressed Neanderthal DNA to neurodegenerative disorders remains uncertain. It is also unclear how common variants associated with neurodegenerative disease risk are maintained by natural selection in the population despite their deleterious effects. In this study, we aimed to quantify the genome-wide contribution of Neanderthal introgression and positive selection to the heritability of complex neurodegenerative disorders to address these questions. We used stratified-linkage disequilibrium score regression to investigate the relationship between five SNP-based signatures of natural selection, reflecting different timepoints of evolution, and genome-wide associated variants of the three most prevalent neurodegenerative disorders: Alzheimer's disease, amyotrophic lateral sclerosis and Parkinson's disease. We found no evidence for enrichment of positively-selected SNPs in the heritability of Alzheimer's disease, amyotrophic lateral sclerosis and Parkinson's disease, suggesting that common deleterious disease variants are unlikely to be maintained by positive selection. There was no enrichment of Neanderthal introgression in the SNP-heritability of these disorders, suggesting that Neanderthal admixture is unlikely to have contributed to disease risk. These findings provide insight into the origins of neurodegenerative disorders within the evolution of Homo sapiens and addresses a long-standing debate, showing that Neanderthal admixture is unlikely to have contributed to common genetic risk of neurodegeneration in anatomically-modern humans.

The Genetics of Intellectual Disability

Intellectual disability (ID) has a prevalence of ~2-3% in the general population, having a large societal impact. The underlying cause of ID is largely of genetic origin; however, identifying this genetic cause has in the past often led to long diagnostic Odysseys. Over the past decades, improvements in genetic diagnostic technologies and strategies have led to these causes being more and more detectable: from cytogenetic analysis in 1959, we moved in the first decade of the 21st century from genomic microarrays with a diagnostic yield of ~20% to next-generation sequencing platforms with a yield of up to 60%. In this review, we discuss these various developments, as well as their associated challenges and implications for the field of ID, which highlight the revolutionizing shift in clinical practice from a phenotype-first into genotype-first approach.

Ultra-rare and common genetic variant analysis converge to implicate negative selection and neuronal processes in the aetiology of schizophrenia

Both common and rare genetic variants (minor allele frequency >1% and <0.1% respectively) have been implicated in the aetiology of schizophrenia. In this study, we integrate single-cell gene expression data with publicly available Genome-Wide Association Study (GWAS) and exome sequenced data in order to investigate in parallel, the enrichment of common and (ultra-)rare variants related to schizophrenia in several functionally relevant gene-sets. Four types of gene-sets were constructed 1) protein-truncating variant (PTV)-intolerant (PI) genes 2) genes expressed in brain cell types and neurons ascertained from mouse and human brain tissue 3) genes defined by synaptic function and location and 4) intersection genes, i.e., PI genes that are expressed in the human and mouse brain cell gene-sets. We show that common as well as ultra-rare schizophrenia-associated variants are overrepresented in PI genes, in excitatory neurons from the prefrontal cortex and hippocampus, medium spiny neurons, and genes enriched for synaptic processes. We also observed stronger enrichment in the intersection genes. Our findings suggest that across the allele frequency spectrum, genes and genetic variants likely to be under stringent selection, and those expressed in particular brain cell types, are involved in the same biological pathways influencing the risk for schizophrenia.

Association of the Combined Effects between Insulin-Like Growth Factor-1 Gene Polymorphisms and Negative Life Events with Major Depressive Disorder among Chinese population in the Context of Oxidative Stress

Background

Oxidative stress may be increased in a number of psychiatric disorders, including major depressive disorder (MDD). MDD has been shown to be related to insulin-like growth factor-1 (IGF-1) as well as to negative life events; exploring the interaction of IGF-1 polymorphisms and negative life events on the risk of MDD is needed. The aim of this study was to analyze the single and combined effects of IGF-1 polymorphisms (rs972936 and rs978458) and negative life events with MDD among Chinese population.

Methods

420 MDD patients (according to DSM-V) and 420 age- and gender-matched control subjects were recruited in a case-control study. Negative life events were assessed using standard rating scales. IGF-1 rs972936 and rs978458 were identified by sequencing. The chi-square (χ²) tests were performed to explore the association of negative life events and IGF-1 polymorphisms with MDD.

Results

Our results found that the negative life events were associated with the risk of MDD (P < 0.001; OR = 3.28, 95% CI: 2.19-4.85). The genotypes of IGF-1 were associated with the risk of MDD (P < 0.001); carrying the IGF-1 rs972936 C allele (OR = 1.53, 95% CI: 1.26-1.85) and rs978458 T allele (OR = 1.92, 95% CI: 1.58-2.34) had a higher risk of MDD. The combined effects between IGF-1 rs978458 and negative life events were associated with the risk of MDD (P < 0.05; OR = 2.94, 95% CI: 1.23-7.03), but IGF-1 rs972936 was not associated (P > 0.05).

Conclusions

Based on the oxidative stress hypothesis, we confirm that carrying IGF-1 rs972936 C allele and rs978458 T allele have a higher risk of MDD and the combined effects between IGF-1 rs978458 and negative life events were associated with the risk of MDD among Chinese population.

Methylation of the serotonin transporter gene moderates the depressive subjective effect of cocaine

Genetic variation in the serotonin transporter (SLC6A4) has been shown to moderate the acute subjective effects of cocaine. Methylation of the SLC6A4 gene is associated with decreased transcription of the serotonin transporter, leading to increased serotonin in the synapse. In this study, methylation of the SLC6A4 gene was investigated in the moderation of the subjective effects of cocaine. Non-treatment-seeking cocaine-dependent individuals (N = 53) were intravenously administered cocaine (40 mg) and saline in a randomized order. The subjective effects of cocaine were self-reported using a visual analog scale starting prior to the administration of cocaine (-15 min) or saline and up to 20 min after infusion. Participants were evaluated for methylation of the SLC6A4 promoter region and 5-HTTLPR genotype. A series of ANCOVAs for SLC6A4 methylation (high/low) were run for each of ten subjective and three cardiovascular effects controlling for age, sex [utilizing the sex-determining region Y protein (SRY)], and population structure (determined from ancestry informative markers and STRUCTURE software). Participants with SLC6A4 hypermethylation reported greater subjective response to cocaine for 'depressed' relative to participants with SLC6A4 hypomethylation (experiment-wise p = 0.002). These findings indicate that SLC6A4 methylation moderates the 'depressed' subjective effect of cocaine in non-treatment-seeking cocaine-dependent participants.

Models of mental health problems: a quasi-systematic review of theoretical approaches

BACKGROUND

Mental health and mental illness have been contested concepts for decades, with a wide variety of models being proposed. To date, there has been no exhaustive review that provides an overview of existing models.

AIM

To conduct a quasi-systematic review of theoretical models of mental health problems.

METHODS

We searched academic databases, reference lists, and an electronic bookshop for literature that proposed, endorsed, reviewed, or critiqued such models. Papers, book chapters, and books were included with material by researchers, clinicians, non-medical professions, and service users writing between 2000 to June 2020 being considered. The study was registered with the Open Science Framework (No. osf.io/r3tjx).

RESULTS

Based on 110 publications, we identified 34 different models which were grouped into five broader categories. Many models bridged two or more categories. Biological and psychological approaches had the largest number of models while social, consumer and cultural models were less diversified. Due to the non-empirical nature of the publications, several limitations in terms of search and quality appraisal apply.

CONCLUSIONS

We conclude that mental health care needs to acknowledge the diversity of theoretical models on mental health problems.

Pharmacogenetics of Addiction Therapy

Drug addiction is a serious relapsing disease that has high costs to society and to the individual addicts. Treatment of these addictions is still in its nascency, with only a few examples of successful therapies. Therapeutic response depends upon genetic, biological, social, and environmental components. A role for genetic makeup in the response to treatment has been shown for several addiction pharmacotherapies with response to treatment based on individual genetic makeup. In this chapter, we will discuss the role of genetics in pharmacotherapies, specifically for cocaine, alcohol, and opioid dependences. The continued elucidation of the role of genetics should aid in the development of new treatments and increase the efficacy of existing treatments.

A recurrent SHANK3 frameshift variant in Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is genetically complex with ~100 copy number variants and genes involved. To try to establish more definitive genotype and phenotype correlations in ASD, we searched genome sequence data, and the literature, for recurrent predicted damaging sequence-level variants affecting single genes. We identified 18 individuals from 16 unrelated families carrying a heterozygous guanine duplication (c.3679dup; p.Ala1227Glyfs*69) occurring within a string of 8 guanines (genomic location [hg38]g.50,721,512dup) affecting SHANK3, a prototypical ASD gene (0.08% of ASD-affected individuals carried the predicted p.Ala1227Glyfs*69 frameshift variant). Most probands carried de novo mutations, but five individuals in three families inherited it through somatic mosaicism. We scrutinized the phenotype of p.Ala1227Glyfs*69 carriers, and while everyone (17/17) formally tested for ASD carried a diagnosis, there was the variable expression of core ASD features both within and between families. Defining such recurrent mutational mechanisms underlying an ASD outcome is important for genetic counseling and early intervention.

Identifying a novel biological mechanism for alcohol addiction associated with circRNA networks acting as potential miRNA sponges

Our lab and others have shown that chronic alcohol use leads to gene and miRNA expression changes across the mesocorticolimbic (MCL) system. Circular RNAs (circRNAs) are noncoding RNAs that form closed-loop structures and are reported to alter gene expression through miRNA sequestration, thus providing a potentially novel neurobiological mechanism for the development of alcohol dependence (AD). Genome-wide expression of circRNA was assessed in the nucleus accumbens (NAc) from 32 AD-matched cases/controls. Significant circRNAs (unadj. p ≤ 0.05) were identified via regression and clustered in circRNA networks via weighted gene co-expression network analysis (WGCNA). CircRNA interactions with previously generated mRNA and miRNA were detected via correlation and bioinformatic analyses. Significant circRNAs (N = 542) clustered in nine significant AD modules (FWER p ≤ 0.05), within which we identified 137 circRNA hubs. We detected 23 significant circRNA-miRNA-mRNA interactions (FDR ≤ 0.10). Among these, circRNA-406742 and miR-1200 significantly interact with the highest number of mRNA, including genes associated with neuronal functioning and alcohol addiction (HRAS, PRKCB, HOMER1, and PCLO). Finally, we integrate genotypic information that revealed 96 significant circRNA expression quantitative trait loci (eQTLs) (unadj. p ≤ 0.002) that showed significant enrichment within recent alcohol use disorder (AUD) and smoking genome-wide association study (GWAS). To our knowledge, this is the first study to examine the role of circRNA in the neuropathology of AD. We show that circRNAs impact mRNA expression by interacting with miRNA in the NAc of AD subjects. More importantly, we provide indirect evidence for the clinical importance of circRNA in the development of AUD by detecting a significant enrichment of our circRNA eQTLs among GWAS of substance abuse.

Antioxidative Defense Genes and Brain Structure in Youth Bipolar Disorder

BACKGROUND

Oxidative stress is implicated in the neuropathology of bipolar disorder (BD). We investigated the association of single-nucleotide polymorphisms (SNPs) in the antioxidative genes superoxide dismutase 2 (SOD2) and glutathione peroxidase 3 (GPX3) with structural neuroimaging phenotypes in youth BD.

METHODS

SOD2 rs4880 and GPX3 rs3792797 SNP genotypes, along with structural magnetic resonance imaging, were obtained from 147 youth (BD = 75; healthy controls = 72). Images were processed using FreeSurfer, yielding surface area, volume, and thickness values for regions of interest (prefrontal cortex [PFC], caudal anterior cingulate cortex, hippocampus) and for vertex-wise whole-brain analysis. Analyses controlled for age, sex, race, and intracranial volume for volume, area, and thickness analyses.

RESULT

Regions of interest analyses revealed diagnosis-by-SOD2 rs4880 interaction effects for caudal anterior cingulate cortex volume and surface area as well as PFC volume; in each case, there was lower volume/area in the BD GG genotype group vs the healthy controls GG genotype group. There was a significant BD diagnosis × GPX3 rs3793797 interaction effect for PFC surface area, where area was lower in the BD A-allele carrier group vs the other genotype groups. Vertex-wise analyses revealed significant interaction effects in frontal, temporal, and parietal regions related to smaller brain structure in the BD SOD2 rs4880 GG group and BD GPX3 rs3793797 A-allele carrier group.

CONCLUSION

We found preliminary evidence that SOD2 rs4880 and GPX3 rs3792797 are differentially associated with brain structures in youth with BD in regions that are relevant to BD. Further studies incorporating additional neuroimaging phenotypes and blood levels of oxidative stress markers are warranted.

Kynurenine pathway: the link between depressive disorders and inflammation

Depression is highly prevalent worldwide and the leading cause of disability. It is believed that currently more than 300 million people of all ages suffer from depression. However, the unambiguous cause of the depression remains unknown. It is suggested that the occurrence of this disease is primarily affected by genetic factors, psychological factors and atypical brain structure or function. Recently, an increasingly important role is attributed to the inflammatory response, which is considered to be the main cause of depression. Activation of the kynurenine pathway (KP) is one of the described mechanisms by which inflammation can induce depression. Kynurenine pathway activation is associated with several neuropsychiatric diseases, including major depression disorder (MDD). The imbalance between the neuroprotective and neurotoxic metabolites in the kynurenine pathway and the associated serotonin and melatonin deficiency, may contribute to the manifestation of depressive symptoms. In this review we discuss the role of the major enzymes of the tryptophan KP: tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) and the role of selected kynurenic metabolites in the depressive disorders. Particular attention was also paid to the genetic basis of depressive disorders and to the summary of current knowledge on the effectiveness of treatment and supplementation with tryptophan and 5-hydroxytryptophan in depression.

Identification of a functional human-unique 351-bp Alu insertion polymorphism associated with major depressive disorder in the 1p31.1 GWAS risk loci

Genome-wide association studies (GWAS) have reported substantial single-nucleotide polymorphisms (SNPs) associated with major depressive disorder (MDD), but the underlying functional variations in the GWAS risk loci are unclear. Here we show that the European MDD genome-wide risk-associated allele of rs12129573 at 1p31.1 is associated with MDD in Han Chinese, and this SNP is in strong linkage disequilibrium (LD) with a human-unique Alu insertion polymorphism (rs70959274) in the 5' flanking region of a long non-coding RNA (lncRNA) LINC01360 (Long Intergenic Non-Protein Coding RNA 1360), which is preferably expressed in human testis in the currently available expression datasets. The risk allele at rs12129573 is almost completely linked with the absence of this Alu insertion. The Alu insertion polymorphism (rs70959274) is significantly associated with a lower RNA level of LINC01360 and acts as a transcription silencer likely through modulating the methylation of its internal CpG sites. Luciferase assays confirm that the presence of Alu insertion at rs70959274 suppresses transcriptional activities in human cells, and deletion of the Alu insertion through CRISPR/Cas9-directed genome editing increases RNA expression of LINC01360. Deletion of the Alu insertion in human cells also leads to dysregulation of gene expression, biological processes and pathways relevant to MDD, such as the alterations of mRNA levels of DRD2 and FLOT1, transcription of genes involved in synaptic transmission, neurogenesis, learning or memory, and the PI3K-Akt signaling pathway. In summary, we identify a human-unique DNA repetitive polymorphism in robust LD with the MDD risk-associated SNP at the prominent 1p31.1 GWAS loci, and offer insights into the molecular basis of the illness.

Evolutionary Ecological Model of Defence Activation Disorders Via the Marginal Value Theorem

OBJECTIVE

Excessive activation of defence modules leads to some dysfunctional outcomes, which can be broadly classified to defence activation disorders. Defence activation disorders have high mortality, low fertility, high prevalence and high heritability. In this study, agent-based simulation model is formulated for solving this evolutionary paradox.

METHODS

The emotional system is considered as a superordinate cognitive module for grasping the average resource amount and the average diminishing returns of resources, based on the Marginal Value Theorem. Under the assumption, the evolutionary ecological model was proposed and analysed.

RESULTS

Individuals utilising suboptimal strategies can be stably maintained in agent-based evolutionary simulation environments. Individuals were adapted to have different d-values according to the local niche. The simulation runs stably within the calibrated range of the variables for a long time. Agents establish locally optimal strategies based on their given d-values, and the relative proportion of subpopulation maintained stably in the heterogeneous habitat with the resource gradient.

CONCLUSION

This study verifies the evolutionary mechanism of defence activation disorders in computer-simulated environments by using agent-based modelling with the Marginal Value Theorem. Balancing selection appears to be a plausible evolutionary mechanism that makes the suboptimal levels of defence activation the evolutionarily stable strategies.

Creativity and Bipolar Disorder: A Shared Genetic Vulnerability

Bipolar disorder is a lifelong mood disorder characterized by extreme mood swings between mania and depression. Despite fitness costs associated with increased mortality and significant impairment, bipolar disorder has persisted in the population with a high heritability and a stable prevalence. Creativity and other positive traits have repeatedly been associated with the bipolar spectrum, particularly among unaffected first-degree relatives and those with milder expressions of bipolar traits. This suggests a model in which large doses of risk variants cause illness, but mild to moderate doses confer advantages, which serve to maintain bipolar disorder in the population. Bipolar disorder may thus be better conceptualized as a dimensional trait existing at the extreme of normal population variation in positive temperament, personality, and cognitive traits, aspects of which may reflect a shared vulnerability with creativity. Investigations of this shared vulnerability may provide insight into the genetic mechanisms underlying illness and suggest novel treatments.

A genome-wide multiphenotypic association analysis identified common candidate genes for subjective well-being, depressive symptoms and neuroticism

Subjective well-being (SWB), depressive symptoms, and neuroticism are common and vital traits of mental disorders. Genetic mechanisms of SWB, depressive symptoms and neuroticism remain elusive now. The large-scale GWAS summary datasets of SWB (n = 229,883), depressive symptoms (n = 180,866), and neuroticism (n = 170,911) were obtained from published studies. MASH tool was applied to the GWAS datasets for identifying candidate SNPs shared by SWB, depressive symptoms and neuroticism. SNPs detected by MASH, were then mapped to target genes considering regulatory SNP (rSNP), methylated quantitative trait locus (MeQTL) and the SNPs near to known genes. Gene set enrichment analysis (GSEA) was conducted by the FUMA platform. A total of 122 candidate SNPs were detected by MASH analysis, mapping to 29 target genes, such as CLDN23, MSRA and XKR6. GO enrichment analysis identified multiple immune related gene sets for SWB, depressive symptoms and neuroticism, such as GSE2770_UNTREATED_VS_IL4_TREATED_ACT_CD4_TCELL_48H_DN (P = 7.32 × 10^-3), GSE6259_FLT3L_INDUCED_DEC205_POS_DC_VS_CD4_TCELL_DN (P = 2.52 × 10^-2). We also found some mental disorders related gene sets were associated with three phenotypes, such as mood instability (P = 1.15 × 10^-6) and neuroticism (P = 1.72 × 10^-6). We identified multiple candidate genes and GO terms shared by SWB, depressive symptoms and neuroticism. Our results support the overlapping genetic mechanisms, and suggest a functional correlation between immunity and SWB, depressive symptoms and neuroticism.

No Evidence for Widespread Positive Selection Signatures in Common Risk Alleles Associated with Schizophrenia

Schizophrenia poses an evolutionary-genetic paradox as it exhibits strongly negative fitness effects (early mortality and decreased fecundity), yet it persists at a prevalence of approximately 1% worldwide. Evidence from several studies have suggested that schizophrenia is evolved and maintained in part as a maladaptive byproduct of recent positive selection and adaptive evolution in human beings. However, inconsistent results have been also proposed, challenging the recent positive selection theory to explain the high population frequency of schizophrenia-associated alleles. Here, we used public domain data to locate signatures of positive selection based on genetic diversity, derived allele frequency, differentiation between populations, and long haplotypes at schizophrenia-associated single nucleotide polymorphisms (SNPs) and randomly selected SNPs (as negative controls). We found evidence for positive selection at 10 out of the 105 schizophrenia-associated SNPs, while 5 of these SNPs involved positive selection for the protective allele. Taken together, the absence of widespread positive selection signals at the schizophrenia-associated SNPs, along with the fact that half of the positive selection favored the protective allele, provide little evidence supporting the positive selection theory in schizophrenia.

Negative symptoms and recollections of parental rejection: The moderating roles of psychological maladjustment and gender

The aim of the study was to investigate the moderating roles of the current self-reported psychological maladjustment and gender in the relationship between perceived parental rejection in childhood and negative symptoms of schizophrenia patients. The study sample consisted of 52 outpatients (20 females and 32 males between the ages of 19 and 61), diagnosed with schizophrenia at Ankara University and Ege University Faculty of Medicine Department of Psychiatry in Turkey. Participants' negative symptoms, recollections of parental rejection, and psychological maladjustment were assessed by Scale for the Assessment of Negative Symptoms, Adult Parental Acceptance-Rejection Questionnaire, and Personality Assessment Questionnaire, respectively. The findings revealed that negative symptoms were not directly linked to maternal and paternal rejection. However, negative symptoms significantly associated with psychological maladjustment. Three-way interaction (moderated moderation) analyses showed that the effects of perceived maternal and paternal rejection in childhood on negative symptoms were significantly moderated by the current self-reported psychological maladjustment for female patients with schizophrenia, but not for males. The study highlighted the importance of applying trauma or attachment-focused interventions and a gender-specific psychiatric treatment in schizophrenia.

The genetics of depression: successful genome-wide association studies introduce new challenges

The recent successful genome-wide association studies (GWASs) for depression have yielded more than 80 replicated loci and brought back the excitement that had evaporated during the years of negative GWAS findings. The identified loci provide anchors to explore their relevance for depression, but this comes with new challenges. Using the watershed model of genotype-phenotype relationships as a conceptual aid and recent genetic findings on other complex phenotypes, we discuss why it took so long and identify seven future challenges. The biggest challenge involves the identification of causal mechanisms since GWAS associations merely flag genomic regions without a direct link to underlying biological function. Furthermore, the genetic association with the index phenotype may also be part of a more extensive causal pathway (e.g., from variant to comorbid condition) or be due to indirect influences via intermediate traits located in the causal pathways to the final outcome. This challenge is highly relevant for depression because even its narrow definition of major depressive disorder captures a heterogeneous set of phenotypes which are often measured by even more broadly defined operational definitions consisting of a few questions (minimal phenotyping). Here, Mendelian randomization and future discovery of additional genetic variants for depression and related phenotypes will be of great help. In addition, reduction of phenotypic heterogeneity may also be worthwhile. Other challenges include detecting rare variants, determining the genetic architecture of depression, closing the "heritability gap", and realizing the potential for personalized treatment. Along the way, we identify pertinent open questions that, when addressed, will advance the field.

How Stress Gets Under the Skin: Early Life Adversity and Glucocorticoid Receptor Epigenetic Regulation

Early life adversity is associated with both persistent disruptions in the hypothalamic-pituitary-adrenal (HPA) axis and psychiatric symptoms. Glucocorticoid receptors (GRs), which are encoded by the NR3C1 gene, bind to cortisol and other glucocorticoids to create a negative feedback loop within the HPA axis to regulate the body's neuroendocrine response to stress. Excess methylation of a promoter sequence within NR3C1 that attenuates GR expression, however, has been associated with both early life adversity and psychopathology. As critical regulators within the HPA axis, GRs and their epigenetic regulation may mediate the link between early life adversity and the onset of psychopathology. The present review discusses this work as one mechanism by which stress may get under the skin to disrupt HPA functioning at an epigenetic level and create long-lasting vulnerabilities in the stress regulatory system that subsequently predispose individuals to psychopathology. Spanning prenatal influences to critical periods of early life and adolescence, we detail the impact that early adversity has on GR expression, physiological responses to stress, and their implications for long-term stress management. We next propose a dual transmission hypothesis regarding both genomic and non-genomic mechanisms by which chronic and acute stress propagate through numerous generations. Lastly, we outline several directions for future research, including potential reversibility of methylation patterns and its functional implications, variation in behavior determined solely by NR3C1, and consensus on which specific promoter regions should be studied.

Surprising conservation of schizophrenia risk genes in lower organisms reflects their essential function and the evolution of genetic liability

Schizophrenia is a devastating psychiatric illness that affects approximately 1% of the population. Genetic variation in multiple genes causes elevated risk for the disorder, but the molecular basis is inadequately understood and it is not clear how risk genes have evolved and persisted in the genome. To address these issues, we have identified orthologs/homologs of 344 schizophrenia risk genes (from the Psychiatric Genomics Consortium dataset) in lower organisms, including C. elegans, Drosophila and zebrafish, along with phenotypes produced by genetic disruption in C. elegans. Schizophrenia risk genes were evolutionarily conserved at significantly higher rates in C. elegans (81%) and zebrafish (88%) than genes in general for these two species (40-70%). The risk-gene equivalents were highly (~3-fold) enriched for essential genes consistent with polygenic mutation threshold models, which propose that genetic susceptibility results from the inevitable expression of harmful combinations of risk variants in the population. Most notably, numerous examples of cross-species synteny revealed how blocks of risk genes geared toward a shared biological purpose coalesced into proximity during evolution. We obtained initial evidence that schizophrenia risk genes affected different stages of development, potentially allowing differential modulation by the environment. Taken together, studies of the conservation of schizophrenia risk genes in simple model organisms provided novel insights into the molecular basis for genetic susceptibility to a complex human psychiatric disorder.

Dvl3 polymorphism interacts with life events and pro-inflammatory cytokines to influence major depressive disorder susceptibility

The purpose of this study is to explore Dvl3 variants and their interaction with negative life events on MDD susceptibility in a Chinese Han population. Additionally, we also attempted to identify whether there is an association between Dvl3 variants and pro-inflammatory cytokines. A total of 1102 participants, consisting of 550 patients with MDD and 552 healthy subjects, were recruited for genotyping by TaqMan allelic discrimination assay. Pro-inflammatory cytokine mRNA levels in peripheral blood were measured by QPCR. After the assessment of negative life events by the Life Events Scale, the Dvl3 gene–environment interaction (G × E) and risk factors were evaluated using generalized multifactor dimensionality reduction method (GMDR) and logistic regression analysis, respectively. This study is the first to reveal the interaction between Dvl3 allelic variations and negative life events as well as pro-inflammatory cytokines on MDD susceptibility in a Chinese Han population.

Parental Unemployment and Offspring Psychotropic Medication Purchases: A Longitudinal Fixed-Effects Analysis of 138,644 Adolescents

Parental unemployment is associated with worse adolescent mental health, but prior evidence has primarily been based on cross-sectional studies subject to reverse causality and confounding. We assessed the association between parental unemployment and changes in adolescent psychotropic medication purchases, with longitudinal individual-level fixed-effects models that controlled for time-invariant confounding. We used data from a large, register-based panel of Finnish adolescents aged 13-20 years in 1987-2012 (n = 138,644) that included annual measurements of mothers' and fathers' employment and offspring psychotropic medication purchases. We assessed changes in the probability of adolescent psychotropic medication purchases in the years before, during, and after the first episode of parental unemployment. There was no association between mother's unemployment and offspring psychotropic purchases in the fixed-effects models, suggesting this association is largely driven by unmeasured confounding and selection. By contrast, father's unemployment led to a significant 15%-20% increase in the probability of purchasing psychotropic medication among adolescents even after extensive controls for observed and unobserved confounding. This change takes at least 1 year to emerge, but it is long-lasting; thus, policies are needed that mitigate the harm of father's unemployment on offspring's mental well-being.

Positive and balancing selection on SLC18A1 gene associated with psychiatric disorders and human-unique personality traits

Maintenance of genetic variants susceptible to psychiatric disorders is one of the intriguing evolutionary enigmas. The present study detects three psychiatric disorder‐relevant genes (CLSTN2, FAT1, and SLC18A1) that have been under positive selection during the human evolution. In particular, SLC18A1 (vesicular monoamine transporter 1; VMAT1) gene has a human‐unique variant (rs1390938, Thr136Ile), which is associated with bipolar disorders and/or the anxiety‐related personality traits. 136Ile shows relatively high (20–61%) frequency in non‐African populations, and Tajima's D reports a significant peak around the Thr136Ile site, suggesting that this polymorphism has been positively maintained by balancing selection in non‐African populations. Moreover, Coalescent simulations predict that 136Ile originated around 100,000 years ago, the time being generally associated with the Out‐of‐Africa migration of modern humans. Our study sheds new light on a gene in monoamine pathway as a strong candidate contributing to human‐unique psychological traits.

A Key Characteristic of Sex Differences in the Developing Brain: Greater Variability in Brain Structure of Boys than Girls

In many domains, including cognition and personality, greater variability is observed in males than in females in humans. However, little is known about how variability differences between sexes are represented in the brain. The present study tested whether there is a sex difference in variance in brain structure using a cohort of 643 males and 591 females aged between 3 and 21 years. The broad age-range of the sample allowed us to test if variance differences in the brain differ across age. We observed significantly greater male than female variance for several key brain structures, including cerebral white matter and cortex, hippocampus, pallidum, putamen, and cerebellar cortex volumes. The differences were observed at both upper and lower extremities of the distributions and appeared stable across development. These findings move beyond mean levels by showing that sex differences were pronounced for variability, thereby providing a novel perspective on sex differences in the developing brain.

Vantage sensitivity: a framework for individual differences in response to psychological intervention

PURPOSE

People differ significantly in their response to psychological intervention, with some benefitting more from treatment than others. According to the recently proposed theoretical framework of vantage sensitivity, some of this variability may be due to individual differences in environmental sensitivity, the inherent ability to register, and process external stimuli. In this paper, we apply the vantage sensitivity framework to the field of psychiatry and clinical psychology, proposing that some people are more responsive to the positive effects of psychological intervention due to heightened sensitivity.

METHODS

After presenting theoretical frameworks related to environmental sensitivity, we review a selection of recent studies reporting individual differences in the positive response to psychological intervention.

RESULTS

A growing number of studies report that some people benefit more from psychological intervention than others as a function of genetic, physiological, and psychological characteristics. These studies support the vantage sensitivity proposition that treatment response is influenced by factors associated with heightened sensitivity to environmental influences. More recently, studies have also shown that sensitivity can be measured with a short questionnaire which appears to predict the response to psychological intervention.

CONCLUSIONS

Vantage sensitivity is a framework with significant relevance for our understanding of widely observed heterogeneity in treatment response. It suggests that variability in response to treatment is partly influenced by people's differing capacity for environmental sensitivity, which can be measured with a short questionnaire. Application of the vantage sensitivity framework to psychiatry and clinical psychology may improve our knowledge regarding when, how, and for whom interventions work.

Recent Advances in the Genetics of Schizophrenia

The last decade brought tremendous progress in the field of schizophrenia genetics. As a result of extensive collaborations and multiple technological advances, we now recognize many types of genetic variants that increase the risk. These include large copy number variants, rare coding inherited and de novο variants, and over 100 loci harboring common risk variants. While the type and contribution to the risk vary among genetic variants, there is concordance in the functions of genes they implicate, such as those whose RNA binds the fragile X-related protein FMRP and members of the activity-regulated cytoskeletal complex involved in learning and memory. Gene expression studies add important information on the biology of the disease and recapitulate the same functional gene groups. Studies of alternative phenotypes help us widen our understanding of the genetic architecture of mental function and dysfunction, how diseases overlap not only with each other but also with non-disease phenotypes. The challenge is to apply this new knowledge to prevention and treatment and help patients. The data generated so far and emerging technologies, including new methods in cell engineering, offer significant promise that in the next decade we will unlock the translational potential of these significant discoveries.

Common schizophrenia alleles are enriched in mutation-intolerant genes and in regions under strong background selection

Schizophrenia is a debilitating psychiatric condition often associated with poor quality of life and decreased life expectancy. Lack of progress in improving treatment outcomes has been attributed to limited knowledge of the underlying biology, although large-scale genomic studies have begun to provide insights. We report a new genome-wide association study of schizophrenia (11,260 cases and 24,542 controls), and through meta-analysis with existing data we identify 50 novel associated loci and 145 loci in total. Through integrating genomic fine-mapping with brain expression and chromosome conformation data, we identify candidate causal genes within 33 loci. We also show for the first time that the common variant association signal is highly enriched among genes that are under strong selective pressures. These findings provide new insights into the biology and genetic architecture of schizophrenia, highlight the importance of mutation-intolerant genes and suggest a mechanism by which common risk variants persist in the population.

Psychosis as an Evolutionary Adaptive Mechanism to Changing Environments

Background: From an evolutionary perspective it is remarkable that psychotic disorders, mostly occurring during fertile age and decreasing fecundity, maintain in the human population. Aim: To argue the hypothesis that psychotic symptoms may not be viewed as an illness but as an adaptation phenomenon, which can become out of control due to different underlying brain vulnerabilities and external stressors, leading to social exclusion. Methods: A literature study and analysis. Results: Until now, biomedical research has not unravelld the definitive etiology of psychotic disorders. Findings are inconsistent and show non-specific brain anomalies and genetic variation with small effect sizes. However, compelling evidence was found for a relation between psychosis and stressful environmental factors, particularly those influencing social interaction. Psychotic symptoms may be explained as a natural defense mechanism or protective response to stressful environments. This is in line with the fact that psychotic symptoms most often develop during adolescence. In this phase of life, leaving the familiar, and safe home environment and building new social networks is one of the main tasks. This could cause symptoms of "hyperconsciousness" and calls on the capacity for social adaptation. Conclusions: Psychotic symptoms may be considered as an evolutionary maintained phenomenon.Research investigating psychotic disorders may benefit from a focus on underlying general brain vulnerabilities or prevention of social exclusion, instead of psychotic symptoms.

Relations among adults' remembrances of parental acceptance-rejection in childhood, self-reported psychological adjustment, and adult psychopathology

AIMS

The aim of the study was to examine relationships among recollections of maternal and paternal acceptance-rejection in childhood and the level of psychological adjustment among adults diagnosed with schizophrenia, social anxiety, and nonclinical control. The study focused primarily on adults with schizophrenia and social anxiety in comparison to nonclinical adults.

METHODS

Fifty-three adults diagnosed with schizophrenia, 51 adults with self-reported social anxiety, and 147 nonclinical controls between the ages of 18 and 62 participated in the study. Data were collected using adult versions of the Parental Acceptance-Rejection Questionnaire for mothers and for fathers, Personality Assessment Questionnaire, Brief Symptom Inventory, Liebowitz Social Anxiety Scale, and the Demographic Information Form.

RESULTS

Findings of analyses showed that participants in the schizophrenia and social anxiety groups remembered having experienced significantly more maternal rejection in childhood than did the nonclinical group. Patient with schizophrenia also reported more recollections of paternal rejection than the nonclinical group. Both clinical groups self-reported more psychological maladjustment than did the nonclinical group. Regression analysis indicated that even though the overall psychological adjustment of adults diagnosed with schizophrenia was predicted by both maternal and paternal acceptance-rejection, psychological adjustment of adults in the social anxiety group was predicted only by maternal (but not paternal) acceptance-rejection.

CONCLUSION

This study provides evidence about the long-lasting associations between adults' recollections of parental acceptance-rejection in childhood and their psychological adjustment in two mental disorders, in which genetic and environmental factors have a different weight.

Reproductive fitness and genetic risk of psychiatric disorders in the general population

The persistence of common, heritable psychiatric disorders that reduce reproductive fitness is an evolutionary paradox. Here, we investigate the selection pressures on sequence variants that predispose to schizophrenia, autism, bipolar disorder, major depression and attention deficit hyperactivity disorder (ADHD) using genomic data from 150,656 Icelanders, excluding those diagnosed with these psychiatric diseases. Polygenic risk of autism and ADHD is associated with number of children. Higher polygenic risk of autism is associated with fewer children and older age at first child whereas higher polygenic risk of ADHD is associated with having more children. We find no evidence for a selective advantage of a high polygenic risk of schizophrenia or bipolar disorder. Rare copy-number variants conferring moderate to high risk of psychiatric illness are associated with having fewer children and are under stronger negative selection pressure than common sequence variants.

Why genetic variants that confer risk for psychiatric disorders persist in the genome is an evolutionary conundrum. Here, Mullins et al. report association of polygenic risk for autism with having fewer children and polygenic risk for ADHD with higher reproductive fitness.

The T Allele of rs8075977 in the 5'-Flanking Region of the PEDF Gene Is Associated with Reduced Risk of Coronary Artery Disease in Elderly Chinese Men

Coronary artery disease (CAD) is a multifactorial disease with a genetic component. Pigment epithelium-derived factor (PEDF) exerts anti-inflammatory, anti-oxidant, anti-thrombotic, and anti-angiogenic effects and thus has received increasing attention as a sensitive biomarker of atherosclerosis and CAD. To explore the potential association between PEDF single nucleotide polymorphisms (SNPs) and CAD, we performed this case-control study of consecutive elderly Chinese Han male patients (n = 416) and age-matched male controls (n = 528) without a history of CAD or electrocardiographic signs of CAD. The enrolled CAD patients (age ≥ 60 years) are not biologically related. A tag approach was used to examine 100% of common variations in the PEDF gene (r² ≥ 0.8, minor allele frequency > 0.1). PEDF tag SNPs (tSNPs) were selected using the HapMap Data-CHB which describes the common patterns of human DNA sequence variation and Tagger program. SNPs were genotyped using ligase detection reaction (LDR). Seven tSNPs (rs8075977, rs11658342, rs1136287, rs12603825, rs12453107, rs6828 and rs11078634) were selected. Among them, only one SNP, rs8075977 (C/T) located in the 5'-flanking region, showed the significant effect on the susceptibility to CAD. The frequency of its T allele was significantly higher in the controls (52.7%) than that in the CAD group (46.2%) (adjusted OR = 0.88, 95% CI: 0.80-0.96; P = 0.005). In conclusion, the T allele of rs8075977 in the 5'-flanking region of the PEDF gene may be protective for CAD. Conversely, the C allele at this variation site is associated with CAD in elderly Chinese Han men.

Epistasis in Neuropsychiatric Disorders

The contribution of epistasis to human disease remains unclear. However, several studies have now identified epistatic interactions between common variants that increase the risk of a neuropsychiatric disorder, while there is growing evidence that genetic interactions contribute to the pathogenicity of rare, multigenic copy-number variants (CNVs) that have been observed in patients. This review discusses the current evidence for epistatic events and genetic interactions in neuropsychiatric disorders, how paradigm shifts in the phenotypic classification of patients would empower the search for epistatic effects, and how network and cellular models might be employed to further elucidate relevant epistatic interactions.

The Genetic Architecture of Major Depressive Disorder in Han Chinese Women

IMPORTANCE

Despite the moderate, well-demonstrated heritability of major depressive disorder (MDD), there has been limited success in identifying replicable genetic risk loci, suggesting a complex genetic architecture. Research is needed to quantify the relative contribution of classes of genetic variation across the genome to inform future genetic studies of MDD.

OBJECTIVES

To apply aggregate genetic risk methods to clarify the genetic architecture of MDD by estimating and partitioning heritability by chromosome, minor allele frequency, and functional annotations and to test for enrichment of rare deleterious variants.

DESIGN, SETTING, AND PARTICIPANTS

The CONVERGE (China, Oxford, and Virginia Commonwealth University Experimental Research on Genetic Epidemiology) study collected data on 5278 patients with recurrent MDD from 58 provincial mental health centers and psychiatric departments of general medical hospitals in 45 cities and 23 provinces of China. Screened controls (n = 5196) were recruited from a range of locations, including general hospitals and local community centers. Data were collected from August 1, 2008, to October 31, 2012.

MAIN OUTCOMES AND MEASURES

Genetic risk for liability to recurrent MDD was partitioned using sparse whole-genome sequencing.

RESULTS

In aggregate, common single-nucleotide polymorphisms (SNPs) explained between 20% and 29% of the variance in MDD risk, and the heritability in MDD explained by each chromosome was proportional to its length (r = 0.680; P = .0003), supporting a common polygenic etiology. Partitioning heritability by minor allele frequency indicated that the variance explained was distributed across the allelic frequency spectrum, although relatively common SNPs accounted for a disproportionate fraction of risk. Partitioning by genic annotation indicated a greater contribution of SNPs in protein-coding regions and within 3'-UTR regions of genes. Enrichment of SNPs associated with DNase I-hypersensitive sites was also found in many tissue types, including brain tissue. Examining burden scores from singleton exonic SNPs predicted to be deleterious indicated that cases had significantly more mutations than controls (odds ratio, 1.009; 95% CI, 1.003-1.014; P = .003), including those occurring in genes expressed in the brain (odds ratio, 1.011; 95% CI, 1.003-1.018; P = .004) and within nuclear-encoded genes with mitochondrial gene products (odds ratio, 1.075; 95% CI, 1.018-1.135; P = .009).

CONCLUSIONS AND RELEVANCE

Results support a complex etiology for MDD and highlight the value of analyzing components of heritability to clarify genetic architecture.

Positive Traits in the Bipolar Spectrum: The Space between Madness and Genius

Bipolar disorder is a severe, lifelong mood disorder for which little is currently understood of the genetic mechanisms underlying risk. By examining related dimensional phenotypes, we may further our understanding of the disorder. Creativity has a historical connection with the bipolar spectrum and is particularly enhanced among unaffected first-degree relatives and those with bipolar spectrum traits. This suggests that some aspects of the bipolar spectrum may confer advantages, while more severe expressions of symptoms negatively influence creative accomplishment. Creativity is a complex, multidimensional construct with both cognitive and affective components, many of which appear to reflect a shared genetic vulnerability with bipolar disorder. It is suggested that a subset of bipolar risk variants confer advantages as positive traits according to an inverted-U-shaped curve with clinically unaffected allele carriers benefitting from the positive traits and serving to maintain the risk alleles in the population. The association of risk genes with creativity in healthy individuals (e.g., NRG1), as well as an overall sharing of common genetic variation between bipolar patients and creative individuals, provides support for this model. Current findings are summarized from a multidisciplinary perspective to demonstrate the feasibility of research in this area to reveal the mechanisms underlying illness.

Interaction of estrogen receptor β and negative life events in susceptibility to major depressive disorder in a Chinese Han female population

BACKGROUND

Both genetic and environmental factors as well as their interaction contribute to the etiology of major depressive disorder (MDD). Estrogen receptor β (ESR2) may play a vital role in the development of MDD in females. The aim of this study is to analyze ESR2 gene polymorphisms and the interaction of ESR2 gene variation and negative life events concerning the risk of developing MDD in females, especially during menopausal stage.

METHODS

Genotyping was performed by Taqman allelic discrimination assay among 191 female MDD patients and 200 healthy females. Life Events Scale and the generalized multifactor dimensionality reduction method were employed to assess the frequency and severity of negative life events and gene-environment interaction (G×E), respectively. All subjects were regrouped into reproductive and menopausal group based on age. Logistic regression was used to evaluate the set of risk factors.

RESULTS

No association of ESR2 G×E interaction with MDD was found in the reproductive group. However, in menopausal females, significant G×E interactions between negative life events and allelic variation of rs1256049 and rs4986938 were observed. Individuals with the A⁺ allele of rs1256049 and rs4986938 were susceptible to MDD when exposed to low negative life events.

LIMITATION

Assessment of negative life events was influenced by subjective interpretation.

CONCLUSIONS

ESR2 may modify the interaction between negative life events and MDD in the Chinese Han menopausal females. To our knowledge, this study is the first to report an effect modification between negative life events and ESR2 variations in female MDD patients.

Adverse Childhood Experiences and Use of Cigarettes and Smokeless Tobacco Products

Adverse childhood experiences (ACEs) have been linked to increased use of tobacco products later in life. However, studies to date have ignored smokeless tobacco products. To address this, data from the 2011 Behavioral Risk Factor Surveillance System, which interviewed adults 18 years and over (N = 102,716) were analyzed. Logistic regression models were fit to estimate odds ratios of ever smoking, current smoking and current smokeless tobacco use in relation to ACEs. Results showed that less than 4 % of respondents currently used smokeless tobacco products, while 44.95 and 18.57 % reported ever and current smoking, respectively. Physical abuse (OR 1.40; 95 % CI 1.14, 1.72), emotional abuse (OR 1.41; 95 % CI 1.19, 1.67), sexual abuse (OR 0.70; 95 % CI 0.51, 0.95), living with a drug user (OR 1.50; 95 % CI 1.17, 1.93), living with someone who was jailed (OR 1.50; 95 % CI 1.11, 2.02) and having parents who were separated or divorced (OR 1.31; 95 % CI 1.09, 1.57) were associated with smokeless tobacco use in unadjusted models. After accounting for confounders, physical abuse (OR 1.43; 95 % CI 1.16, 1.78), emotional abuse (OR 1.32; 95 % CI 1.10, 1.57), living with a problem drinker (OR 1.30; 95 % CI 1.08, 1.58), living with a drug user (OR 1.31; 95 % CI 1.00, 1.72) and living with adults who treated each other violently (OR 1.30; 95 % CI 1.05, 1.62) were associated with smokeless tobacco use. Living with someone who was mentally ill (OR 0.70; 95 % CI 0.53, 0.92) was associated with smokeless tobacco use after accounting for confounders and all ACEs. Results indicated that some childhood adversities are associated with use of smokeless tobacco products. Special attention is needed to prevent tobacco use of different types among those experiencing ACEs.

Genetic Markers of Human Evolution Are Enriched in Schizophrenia

BACKGROUND

Why schizophrenia has accompanied humans throughout our history despite its negative effect on fitness remains an evolutionary enigma. It is proposed that schizophrenia is a by-product of the complex evolution of the human brain and a compromise for humans' language, creative thinking, and cognitive abilities.

METHODS

We analyzed recent large genome-wide association studies of schizophrenia and a range of other human phenotypes (anthropometric measures, cardiovascular disease risk factors, immune-mediated diseases) using a statistical framework that draws on polygenic architecture and ancillary information on genetic variants. We used information from the evolutionary proxy measure called the Neanderthal selective sweep (NSS) score.

RESULTS

Gene loci associated with schizophrenia are significantly (p = 7.30 × 10(-9)) more prevalent in genomic regions that are likely to have undergone recent positive selection in humans (i.e., with a low NSS score). Variants in brain-related genes with a low NSS score confer significantly higher susceptibility than variants in other brain-related genes. The enrichment is strongest for schizophrenia, but we cannot rule out enrichment for other phenotypes. The false discovery rate conditional on the evolutionary proxy points to 27 candidate schizophrenia susceptibility loci, 12 of which are associated with schizophrenia and other psychiatric disorders or linked to brain development.

CONCLUSIONS

Our results suggest that there is a polygenic overlap between schizophrenia and NSS score, a marker of human evolution, which is in line with the hypothesis that the persistence of schizophrenia is related to the evolutionary process of becoming human.

Genetic mapping of canine fear and aggression

BACKGROUND

Fear/anxiety and anger/aggression greatly influence health, quality of life and social interactions. They are a huge burden to wellbeing, and personal and public economics. However, while much is known about the physiology and neuroanatomy of such emotions, little is known about their genetics - most importantly, why some individuals are more susceptible to pathology under stress.

RESULTS

We conducted genomewide association (GWA) mapping of breed stereotypes for many fear and aggression traits across several hundred dogs from diverse breeds. We confirmed those findings using GWA in a second cohort of partially overlapping breeds. Lastly, we used the validated loci to create a model that effectively predicted fear and aggression stereotypes in a third group of dog breeds that were not involved in the mapping studies. We found that i) known IGF1 and HMGA2 loci variants for small body size are associated with separation anxiety, touch-sensitivity, owner directed aggression and dog rivalry; and ii) two loci, between GNAT3 and CD36 on chr18, and near IGSF1 on chrX, are associated with several traits, including touch-sensitivity, non-social fear, and fear and aggression that are directed toward unfamiliar dogs and humans. All four genome loci are among the most highly evolutionarily-selected in dogs, and each of those was previously shown to be associated with morphological traits. We propose that the IGF1 and HMGA2 loci are candidates for identical variation being associated with both behavior and morphology. In contrast, we show that the GNAT3-CD36 locus has distinct variants for behavior and morphology. The chrX region is a special case due to its extensive linkage disequilibrium (LD). Our evidence strongly suggests that sociability (which we propose is associated with HS6ST2) and fear/aggression are two distinct GWA loci within this LD block on chrX, but there is almost perfect LD between the peaks for fear/aggression and animal size.

CONCLUSIONS

We have mapped many canine fear and aggression traits to single haplotypes at the GNAT3-CD36 and IGSF1 loci. CD36 is widely expressed, but areas of the amygdala and hypothalamus are among the brain regions with highest enrichment; and CD36-knockout mice are known to have significantly increased anxiety and aggression. Both of the other genes have very high tissue-specificity and are very abundantly expressed in brain regions that comprise the core anatomy of fear and aggression - the amygdala to hypothalamic-pituitary-adrenal (HPA) axis. We propose that reduced-fear variants at these loci may have been involved in the domestication process.

Risk of psychiatric illness from advanced paternal age is not predominantly from de novo mutations

The offspring of older fathers have higher risk of psychiatric disorders such as schizophrenia and autism. Paternal-age-related de novo mutations are widely assumed to be the underlying causal mechanism, and, although such mutations must logically make some contribution, there are alternative explanations (for example, elevated liability to psychiatric illness may delay fatherhood). We used population genetic models based on empirical observations of key parameters (for example, mutation rate, prevalence, and heritability) to assess the genetic relationship between paternal age and risk of psychiatric illness. These models suggest that age-related mutations are unlikely to explain much of the increased risk of psychiatric disorders in children of older fathers. Conversely, a model incorporating a weak correlation between age at first child and liability to psychiatric illness matched epidemiological observations. Our results suggest that genetic risk factors shared by older fathers and their offspring are a credible alternative explanation to de novo mutations for risk to children of older fathers.

Drugs as instruments: a new framework for non-addictive psychoactive drug use

Most people who are regular consumers of psychoactive drugs are not drug addicts, nor will they ever become addicts. In neurobiological theories, non-addictive drug consumption is acknowledged only as a "necessary" prerequisite for addiction, but not as a stable and widespread behavior in its own right. This target article proposes a new neurobiological framework theory for non-addictive psychoactive drug consumption, introducing the concept of "drug instrumentalization." Psychoactive drugs are consumed for their effects on mental states. Humans are able to learn that mental states can be changed on purpose by drugs, in order to facilitate other, non-drug-related behaviors. We discuss specific "instrumentalization goals" and outline neurobiological mechanisms of how major classes of psychoactive drugs change mental states and serve non-drug-related behaviors. We argue that drug instrumentalization behavior may provide a functional adaptation to modern environments based on a historical selection for learning mechanisms that allow the dynamic modification of consummatory behavior. It is assumed that in order to effectively instrumentalize psychoactive drugs, the establishment of and retrieval from a drug memory is required. Here, we propose a new classification of different drug memory subtypes and discuss how they interact during drug instrumentalization learning and retrieval. Understanding the everyday utility and the learning mechanisms of non-addictive psychotropic drug use may help to prevent abuse and the transition to drug addiction in the future.

Early life adversity and serotonin transporter gene variation interact to affect DNA methylation of the corticotropin-releasing factor gene promoter region in the adult rat brain

The interaction between childhood maltreatment and the serotonin transporter (5-HTT) gene linked polymorphic region has been associated with increased risk to develop major depression. This Gene × Environment interaction has furthermore been linked with increased levels of anxiety and glucocorticoid release upon exposure to stress. Both endophenotypes are regulated by the neuropeptide corticotropin-releasing factor (CRF) or hormone, which is expressed by the paraventricular nucleus of the hypothalamus, the bed nucleus of the stria terminalis, and the central amygdala (CeA). Therefore, we hypothesized that altered regulation of the expression of CRF in these areas represents a major neurobiological mechanism underlying the interaction of early life stress and 5-HTT gene variation. The programming of gene transcription by Gene × Environment interactions has been proposed to involve epigenetic mechanisms such as DNA methylation. In this study, we report that early life stress and 5-HTT genotype interact to affect DNA methylation of the Crf gene promoter in the CeA of adult male rats. Furthermore, we found that DNA methylation of a specific site in the Crf promoter significantly correlated with CRF mRNA levels in the CeA. Moreover, CeA CRF mRNA levels correlated with stress coping behavior in a learned helplessness paradigm. Together, our findings warrant further investigation of the link of Crf promoter methylation and CRF expression in the CeA with behavioral changes that are relevant for psychopathology.

Using Evolutionary Theory to Guide Mental Health Research

Evolutionary approaches to medicine can shed light on the origins and etiology of disease. Such an approach may be especially useful in psychiatry, which frequently addresses conditions with heterogeneous presentation and unknown causes. We review several previous applications of evolutionary theory that highlight the ways in which psychiatric conditions may persist despite and because of natural selection. One lesson from the evolutionary approach is that some conditions currently classified as disorders (because they cause distress and impairment) may actually be caused by functioning adaptations operating "normally" (as designed by natural selection). Such conditions suggest an alternative illness model that may generate alternative intervention strategies. Thus, the evolutionary approach suggests that psychiatry should sometimes think differently about distress and impairment. The complexity of the human brain, including normal functioning and potential for dysfunctions, has developed over evolutionary time and has been shaped by natural selection. Understanding the evolutionary origins of psychiatric conditions is therefore a crucial component to a complete understanding of etiology.

Interaction of tryptophan hydroxylase 2 gene and life events in susceptibility to major depression in a Chinese Han population

BACKGROUND

Major depression (MD) results from a complex synergy between genetic and environmental factors. The aim of this study is to analyze the interaction of tryptophan hydroxylase 2 gene (TPH2) variation and negative life events in the pathogenesis of MD. Three TPH2 polymorphisms, -703G/T (rs4570625), -473T/A (rs11178997), and 1463G/A (rs120074175), were selected based on previous findings of associations with MD.

METHODS

In this study, 289 patients with MD and 289 age- and sex-matched control subjects were genotyped. The frequency and severity of negative life events were assessed by the Life Events Scale (LES). Gene-environment interactions (G×E) were assessed using the generalized multifactor dimensionality reduction (GMDR) method.

RESULTS

Differences in rs11178997 and rs120074175 allele frequencies and genotype distributions were observed between MD patients and controls. Significant G×E interactions between negative life events and allelic variation of rs4570625, rs11178997, and rs120074175 were also observed. Individuals carrying the T(-) genotype of rs4570625 (GG), T(-) genotype of rs11178997 (AA), or A(-) genotype of rs120074175 (GG) were susceptible to MD only when exposed to high-negative life events. However, individuals with the T(+) genotypes of rs11178997 (TA, TT) and A(+) genotypes of rs120074175 (AG, AA) were susceptible to MD when exposed to low-negative life events.

LIMITATION

Assessment of negative life events was influenced by subjective interpretation.

CONCLUSIONS

Interactions between multiple TPH2 gene alleles and negative life events were revealed by GMDR analysis. Chinese Han individuals with at least one rs11178997 T allele or rs120074175 A allele are susceptible to MD even in the relative absence of high-negative life events.

Overview of genetic research in anorexia nervosa: The past, the present and the future

BACKGROUND

Even though the evidence supporting the presence of a heritable component in the aetiology of anorexia nervosa (AN) is strong, the underlying genetic mechanisms remain poorly understood. The recent publication of a genome-wide association study (GWAS) of AN (Boraska, Mol Psychiatry, 2014) was an important step in genetic research in AN.

OBJECTIVE

To briefly sum up strengths and weaknesses of candidate-gene and genome-wide approaches, to discuss the genome-wide association studies of AN and to make predictions about the genetic architecture of AN by comparing it to that of schizophrenia (since the diseases share some similarities and genetic research in schizophrenia is more advanced).

METHOD

Descriptive literature review.

RESULTS

Despite remarkable efforts, the gene-association studies in AN did not advance our knowledge as much as had been hoped, although some results still await replication.

DISCUSSION

Continuous effort of participants, clinicians and researchers remains necessary to ensure that genetic research in AN follows a similarly successful path as in schizophrenia. Identification of genetic susceptibility loci provides a basis for follow-up studies.