Genetics of anxiety disorders: the complex road from DSM to DNA

Genetic Vulnerability to Social Anxiety Disorder

Most anxiety disorders 'run within families': people suffering from an anxiety disorder often have family members who are highly anxious as well. In this chapter, we explore recent work devoted to unraveling the complex interplay between genes and environment in the development of anxiety. We review studies focusing on the genetic vulnerability to develop social anxiety disorder (SAD), as SAD is one of the most prevalent anxiety disorders, with an early onset, a chronic course, and associated with significant life-long impairments. More insight into the development of SAD is thus of uttermost importance.First, we will discuss family studies, twin studies, and large-sized population-based registry studies and explain what these studies can reveal about the genetic vulnerability to develop anxiety. Next, we describe the endophenotype approach; in this context, we will summarize results from the Leiden Family Lab study on Social Anxiety Disorder. Subsequently, we review the relationship between the heritable trait 'behavioral inhibition' and the development of SAD, and highlight the relevance of this work for the development and improvement of preventative and therapeutic interventions for socially anxious youth.

Burden and risk factors of anxiety disorders among Arabic pediatric population: A systematic review

<b>Aim:</b> In the general population, where 6 to 20% of individuals experience anxiety disorders, children also experience a higher burden of anxiety. We undertook a systematic review In order to examine and summarize the results from studies that estimated the prevalence of anxiety and/or its associated risk factors in the pediatric populations of Arab nations, primarily the gulf countries.<br /> <b>Methods:</b> Any study that focused on the pediatric population and completed in Arab nations to determine the incidence of anxiety and/or its risk factors among children under the age of 18. The review had 13 articles were included.<br /> <b>Results:</b> The results of the systematic review found that there was a wide variation in the prevalence of anxiety among children. At least 30.2% of the children were found to suffer from anxiety and the prevalence could go up to 60% in some countries with a higher prevalence among girls than boys. Associated factors of anxiety were diverse including exposure to environmental tobacco smoke, parenting style, living with parents suffering from mental disorders, school type, and being female.<br /> <b>Conclusion:</b> The findings of the review demonstrate the higher prevalence of anxiety among children as almost at least one-third of children suffer from anxiety in the Gulf countries. The program managers and the respective government of these Arab countries need to devise some strategies and interventions that not only focus on the children but also their environment.

Cognitive and Mental Health of Young Mothers' Offspring: A Meta-analysis

BACKGROUND AND OBJECTIVES

The nature and magnitude of the cognitive and mental health risks among the offspring of young mothers is not fully understood. Our objective is to examine the risk of mental disorders in these offspring.

METHODS

Five databases (Medline, Embase, Web of Science, PsycINFO, and CINAHL) were searched from their inceptions until February 2022. Studies were eligible if they assessed offspring of young mothers (&lt;21 years), contained a control group, and assessed any cognitive and/or mental health outcomes. Random-effects meta-analysis was used to generate standardized mean differences (SMDs) in infants (0-3 years), children (4-9), adolescents (10-19), and adults (20+). Methodological bias was assessed using the Newcastle-Ottawa Scale.

RESULTS

51 outcomes were meta-analyzed. Levels of cognitive and learning problems were higher among the infants (SMD = 0.30 [95% confidence interval 0.0-0.55]) and adolescents (SMD = 0.43 [0.24 to 0.62]) of young mothers. Adolescents had more symptoms of delinquency (SMD = 0.24 [0.12 to 0.36]). As adults, they are more often convicted of violent crimes (SMD = 0.36 [0.22 to 0.50]). Internalizing symptoms were higher in these offspring in childhood (SMD = 0.29 [0.14 to 0.45]) and adulthood (SMD = 0.35 [0.34 to 0.36]). This review uses unadjusted data and is thus unequipped to infer causality. Studies have high attrition and rely heavily on self-report.

CONCLUSIONS

Young mothers' offspring have more cognitive, externalizing, and internalizing problems across the lifespan than individuals born to mothers ≥21 years of age. They may benefit from early detection and support.

Causality of genetically determined metabolites on anxiety disorders: a two-sample Mendelian randomization study

BACKGROUND

Although anxiety disorders are one of the most prevalent mental disorders, their underlying biological mechanisms have not yet been fully elucidated. In recent years, genetically determined metabolites (GDMs) have been used to reveal the biological mechanisms of mental disorders. However, this strategy has not been applied to anxiety disorders. Herein, we explored the causality of GDMs on anxiety disorders through Mendelian randomization study, with the overarching goal of unraveling the biological mechanisms.

METHODS

A two-sample Mendelian randomization (MR) analysis was implemented to assess the causality of GDMs on anxiety disorders. A genome-wide association study (GWAS) of 486 metabolites was used as the exposure, whereas four different GWAS datasets of anxiety disorders were the outcomes. Notably, all datasets were acquired from publicly available databases. A genetic instrumental variable (IV) was used to explore the causality between the metabolite and anxiety disorders for each metabolite. The MR Steiger filtering method was implemented to examine the causality between metabolites and anxiety disorders. The standard inverse variance weighted (IVW) method was first used for the causality analysis, followed by three additional MR methods (the MR-Egger, weighted median, and MR-PRESSO (pleiotropy residual sum and outlier) methods) for sensitivity analyses in MR analysis. MR-Egger intercept, and Cochran's Q statistical analysis were used to evaluate possible heterogeneity and pleiotropy. Bonferroni correction was used to determine the causative association features (P < 1.03 × 10^-4). Furthermore, metabolic pathways analysis was performed using the web-based MetaboAnalyst 5.0 software. All statistical analysis were performed in R software. The STROBE-MR checklist for the reporting of MR studies was used in this study.

RESULTS

In MR analysis, 85 significant causative relationship GDMs were identified. Among them, 11 metabolites were overlapped in the four different datasets of anxiety disorders. Bonferroni correction showing1-linoleoylglycerophosphoethanolamine (OR_{fixed-effect IVW} = 1.04; 95% CI 1.021-1.06; P_{fixed-effect IVW} = 4.3 × 10^-5) was the most reliable causal metabolite. Our results were robust even without a single SNP because of a "leave-one-out" analysis. The MR-Egger intercept test indicated that genetic pleiotropy had no effect on the results (intercept = - 0.0013, SE = 0.0006, P = 0.06). No heterogeneity was detected by Cochran's Q test (MR-Egger. Q = 7.68, P = 0.742; IVW. Q = 12.12, P = 0.436). A directionality test conducted by MR Steiger confirmed our estimation of potential causal direction (P < 0.001). In addition, two significant pathways, the "primary bile acid biosynthesis" pathway (P = 0.008) and the "valine, leucine, and isoleucine biosynthesis" pathway (P = 0.03), were identified through metabolic pathway analysis.

CONCLUSION

This study provides new insights into the causal effects of GDMs on anxiety disorders by integrating genomics and metabolomics. The metabolites that drive anxiety disorders may be suited to serve as biomarkers and also will help to unravel the biological mechanisms of anxiety disorders.

Systematic review of genome-wide association studies of anxiety disorders and neuroticism

OBJECTIVES

To summarise SNP associations identified by genome-wide association studies (GWASs) of anxiety disorders and neuroticism; to appraise the quality of individual studies, and to assess the ancestral diversity of study participants.

METHODS

We searched PubMed, Scopus, PsychInfo and PubPsych for GWASs of anxiety disorders, non-diagnostic traits (such as anxiety sensitivity), and neuroticism, and extracted all SNPs that surpassed genome-wide significance. We graded study quality using Q-genie scores and reviewed the ancestral diversity of included participants.

RESULTS

32 studies met our inclusion criteria. A total of 563 independent significant variants were identified, of which 29 were replicated nominally in independent samples, and 3 were replicated significantly. The studies had good global quality, but many smaller studies were underpowered. Phenotypic heterogeneity for anxiety (and less so for neuroticism) seemed to reflect the complexity of capturing this trait. Ancestral diversity was poor, with 70% of studies including only populations of European ancestry.

CONCLUSION

The functionality of genes identified by GWASs of anxiety and neuroticism deserves further investigation. Future GWASs should have larger sample sizes, more rigorous phenotyping and include more ancestrally diverse population groups.

Systematic Review: Molecular Studies of Common Genetic Variation in Child and Adolescent Psychiatric Disorders

OBJECTIVE

A systematic review of studies using molecular genetics and statistical approaches to investigate the role of common genetic variation in the development, persistence, and comorbidity of childhood psychiatric traits was conducted.

METHOD

A literature review was performed using the PubMed database, following PRISMA guidelines. There were 131 studies meeting inclusion criteria, having investigated at least one type of childhood-onset or childhood-measured psychiatric disorder or trait with the aim of identifying trait-associated common genetic variants, estimating the contribution of single nucleotide polymorphisms (SNPs) to the amount of variance explained (SNP-based heritability), investigating genetic overlap between psychiatric traits, or investigating whether the stability in traits or the association with adult traits is explained by genetic factors.

RESULTS

The first robustly associated genetic variants have started to be identified for childhood psychiatric traits. There were substantial contributions of common genetic variants to many traits, with variation in single nucleotide polymorphism heritability estimates depending on age and raters. Moreover, genetic variants also appeared to explain comorbidity as well as stability across a range of psychiatric traits in childhood and across the life span.

CONCLUSION

Common genetic variation plays a substantial role in childhood psychiatric traits. Increased sample sizes will lead to increased power to identify genetic variants and to understand genetic architecture, which will ultimately be beneficial to targeted and prevention strategies. This can be achieved by harmonizing phenotype measurements, as is already proposed by large international consortia and by including the collection of genetic material in every study.

Generalized and social anxiety disorder interactomes show distinctive overlaps with striosome and matrix interactomes

Mechanisms underlying anxiety disorders remain elusive despite the discovery of several associated genes. We constructed the protein-protein interaction networks (interactomes) of six anxiety disorders and noted enrichment for striatal expression among common genes in the interactomes. Five of these interactomes shared distinctive overlaps with the interactomes of genes that were differentially expressed in two striatal compartments (striosomes and matrix). Generalized anxiety disorder and social anxiety disorder interactomes showed exclusive and statistically significant overlaps with the striosome and matrix interactomes, respectively. Systematic gene expression analysis with the anxiety disorder interactomes constrained to contain only those genes that were shared with striatal compartment interactomes revealed a bifurcation among the disorders, which was influenced by the anterior cingulate cortex, nucleus accumbens, amygdala and hippocampus, and the dopaminergic signaling pathway. Our results indicate that the functionally distinct striatal pathways constituted by the striosome and the matrix may influence the etiological differentiation of various anxiety disorders.

The risk of anxiety disorders in children of parents with severe psychiatric disorders: a systematic review and meta-analysis

BACKGROUND

Several studies have investigated the association between parental severe psychiatric disorders and anxiety disorder risk in offspring, but the findings across these studies have been inconsistent.

METHODS

Using the PRISMA guideline, a rigorous electronic and manual search was conducted in four electronic databases EMBASE, PubMed, PsychINFO, and Scopus to identify relevant studies. All observation studies (cohort and case-control studies) that examined the association between parental severe psychiatric disorders and the risk of offspring anxiety disorders were identified. Summary risk ratios (RRs) and 95% confidence intervals (95%CI) were synthesized using a fixed and random effect meta-analysis.

RESULTS

Twenty-five studies were included in the final analysis (14 cohort and 11 case-control studies). The meta-analysis showed that parental severe psychiatric disorder was associated with a higher risk of social phobia, panic, obsessive-compulsive, post-traumatic stress, separation anxiety, and generalized anxiety disorders in the offspring. When considering specific severe psychiatric disorders in parents as exposure, parental bipolar disorder was associated with an increased risk of obsessive-compulsive and generalized anxiety disorders in the offspring, whereas parental depressive disorder was associated with an increased risk of social phobia, separation anxiety, and generalized anxiety disorders in the offspring. Conversely, parental schizophrenia was not associated with offspring anxiety disorder CONCLUSION: This review suggests that the offspring of parents with severe psychiatric, bipolar, and depressive disorders are at an increased risk of developing a range of anxiety disorders. These findings suggest that targeted early screening and intervention programs are imperative in exposed offspring.

Discrimination and anxiety: Using multiple polygenic scores to control for genetic liability

An established body of research indicates that discrimination is associated with increased symptoms of anxiety and negative affect. However, the association cannot be interpreted unambiguously as an exposure effect because a common set of genetic factors can simultaneously contribute to increased liability for symptoms of anxiety, negative affect, and the perception of discrimination. The present study elucidates the association between discrimination and anxiety/negative affect by implementing strict genetic controls in a large sample of adults. We used data from the biomarker project of the Study of Midlife Development in the United States (MIDUS), a national probability sample of noninstitutionalized, English-speaking respondents aged 25 to 74 y. Participants who consented to provide genetic data were biologically unrelated and of European ancestry as determined by genotype principal components analysis (n = 1,146). A single structural regression model was fit to the data with three measures of discrimination specified to load onto a latent factor and six measures of anxiety and negative affect specified to load onto a second latent factor. After accounting for potential genetic confounds-polygenic scores for anxiety, depression, and neuroticism and the first five genetic principal components-greater discrimination was associated with greater anxiety/negative affect (β = 0.53, SE = 0.04, P < 0.001). Findings suggest that measures of perceived discrimination should be considered environmental risk factors for anxiety/negative affect rather than indices of genetic liability for anxiety, depression, or neuroticism. Clinical interventions and prevention measures should focus on ways to mitigate the impact of discrimination to improve mental health at the population level.

Central and Peripheral Symptoms in Network Analysis are Differentially Heritable A Twin Study of Anxious Misery

BACKGROUND

Evidence suggests that depression and anxiety disorders are genetically based. Although symptoms of these internalizing disorders tend to correlate, the degree to which the related symptoms are heritable is unclear. This overlap has been conceptualized as Anxious Misery and existing research examining similar constructs of negative affect has revealed moderate heritability. However, it is unclear if some symptoms that characterize these constructs are more heritable than others. Modeling the symptom structure of Anxious Misery and examining which symptoms are most heritable may have implications for etiological models of internalizing disorders. Accordingly, the present study employed network analysis to explore the relationships across symptoms of Anxious Misery and to test if central symptoms in the network, compared to more peripheral symptoms, differ in their heritabilities.

METHODS

Twin pairs (N = 1,344 pairs) with a mean age of 39 years (SD = 16 years) completed measures of anxiety and neuroticism to represent the Anxious Misery network.

RESULTS

Panic-related symptoms were the most central in the network and were the most heritable, with genetic factors accounting for up to 59% of phenotypic variance. Peripheral symptoms were less heritable, accounting for as little as 21% of phenotypic variance. The degree of symptom heritability was strongly correlated with the degree of centrality of a symptom in the network (r = .53).

LIMITATIONS

Reliance on two self-report measures to represent Anxious Misery limits the generalizability of the findings.

CONCLUSIONS

Central and peripheral symptoms of an Anxious Misery network may differ in degree of heritability.

A novel-odour exploration test for measuring anxiety in adult and larval zebrafish

BACKGROUND

Existing methods to assess anxiety in zebrafish are mostly based on visual exploration. However, evidence suggests that zebrafish are more attuned to olfactory than visual stimuli. We developed a novel-odour exploration test (NOEt) for zebrafish.

NEW METHOD

Adult zebrafish were exposed to a stimulus sponge soaked with olfactory cue and a control sponge with no cue, placed at the extremities of a narrow, rectangular tank. We scored time spent close to the two sponges to calculate the attraction towards the olfactory cue. In experiment 1, we tested adult zebrafish in the NOEt using various olfactory cues. In experiment 2, we tested larvae. In experiment 3, we compared the NOEt with the most used method to assess anxiety, the open-field test.

RESULTS

In experiment 1, zebrafish responded markedly to cues, by either approaching or avoiding the soaked sponge according to the type of cue. The temporal pattern of exploration toward the cue was similar to that of novel objects' exploration in this species. In experiment 2, larvae responded to novel odours, but differently from adults. In experiment 3, we found a relationship between the NOEt and the open-field test.

COMPARISON WITH EXISTING METHOD(S)

Compared to existing tests, the NOEt has the advantage of exploiting the preferred sensory modality of zebrafish. Moreover, it can be used in early stages because olfactory receptors develop early in this species.

CONCLUSIONS

The NOEt is a simple, rapid and low-cost test to study anxiety in zebrafish using the spontaneous exploration of novel olfactory cues.

Psychobiotics Regulate the Anxiety Symptoms in Carriers of Allele A of IL-1β Gene: A Randomized, Placebo-Controlled Clinical Trial

Background

Probiotic oral intake, via modulation of the microbiota-gut-brain axis, can impact brain activity, mood, and behavior; therefore, it may be beneficial against psychological distress and anxiety disorders. Inflammatory cytokines can influence the onset and progression of several neurodegenerative mood disorders, and the IL-1β rs16944 SNP is related to high cytokine levels and potentially affects mood disorders. The aim of this study was to examine the combined effect of IL-1β polymorphism and probiotic administration in mood disorder phenotypes in the Italian population.

Methods

150 subjects were randomized into two different groups, probiotic oral suspension group (POSG) and placebo control group (PCG), and received the relative treatment for 12 weeks. Psychological profile assessment by Hamilton Anxiety Rating Scale (HAM-A), Body Uneasiness Test (BUT), and Symptom Checklist 90-Revised (SCL90R) was administered to all volunteers. Genotyping was performed on DNA extracted from salivary samples.

Results

After 12 weeks of intervention, a significant reduction of HAM-A total score was detected in the POSG (p < 0.01), compared to the PCG. Furthermore, IL-1β carriers have moderate risk to develop anxiety (OR = 5.90), and in POSG IL-1β carriers, we observed a reduction of HAM-A score (p = 0.02).

Conclusions

Consumption of probiotics mitigates anxiety symptoms, especially in healthy adults with the minor A allele of rs16944 as a risk factor. Our results encourage the use of probiotics in anxiety disorders and suggest genetic association studies for psychobiotic-personalized therapy.

Translational Studies in the Complex Role of Neurotransmitter Systems in Anxiety and Anxiety Disorders

Discovery of innovative anxiolytics is severely hampering. Existing anxiolytics are developed decades ago and are still the therapeutics of choice. Moreover, lack of new drug targets forecasts a severe jeopardy in the future treatment of the huge population of CNS-diseased patients. We simply lack the knowledge on what is wrong in brains of anxious people (normal and diseased). Translational research, based on interacting clinical and preclinical research, is extremely urgent. In this endeavor, genetic and genomic approaches are part of the spectrum of contributing factors. We focus on three druggable targets: serotonin transporter, 5-HT_1A, and GABA_A receptors. It is still uncertain whether and how these targets are involved in normal and diseased anxiety processes. For serotonergic anxiolytics, the slow onset of action points to indirect effects leading to plasticity changes in brain systems leading to reduced anxiety. For GABA_A benzodiazepine drugs, acute anxiolytic effects are found indicating primary mechanisms directly influencing anxiety processes. Close translational collaboration between fundamental academic and discovery research will lead to badly needed breakthroughs in the search for new anxiolytics.

Attenuation of compulsive-like behavior by fluvoxamine in a non-induced mouse model of obsessive-compulsive disorder

The current study evaluated the role of strain and compulsive trait differences in response to fluvoxamine, a common obsessive-compulsive disorder (OCD) drug, in two different mouse strains (BIG1 and BIG2) with a spontaneous compulsive-like phenotype. For compulsive-like nest-building behavior, dose-dependent attenuation of nesting by fluvoxamine was observed for the BIG1 compulsive-like strain during the first hour after administration. No significant differences were found for the BIG2 strain during the first hour, although a dose-dependent trend similar to that in the BIG1 strain was observed. Fluvoxamine dose dependently decreased the number of marbles buried in both strains 1 h after administration. For anxiety-like behaviors in the open field, no significant drug effects were found for the latency to leave the center and the number of line crossings. Significant strain differences were observed, with the BIG2 strain showing higher anxiety-like behaviors and reduced locomotor activity compared with the BIG1 strain. Consequently, this study adds predictive validity to our mouse model of OCD, whereas the anxiety-like differences between the strains add heterogeneity to our mouse model, similar to the heterogeneity observed in OCD.

Association between genes on chromosome 19p13.2 and panic disorder

Panic disorder (PD) is a severe and disabling mental disorder, which is moderately heritable. In a previous study, we carried out a genome-wide association study using patients with PD and control individuals from the isolated population of the Faroe Islands and identified chromosome 19p13.2 as a candidate region. To further investigate this chromosomal region for association with PD, we analysed eight single nucleotide polymorphisms (SNPs) in three candidate genes - small-nuclear RNA activating complex, polypeptide 2 (SNAPC2), mitogen-activated protein kinase kinase 7 (MAP2K7) and leucine-rich repeat containing 8 family, member E (LRRC8E) - these genes have previously been directly or indirectly implicated in other mental disorders. A total of 511 patients with PD and 1029 healthy control individuals from the Faroe Islands, Denmark and Germany were included in the current study. SNPs covering the gene region of SNAPC2, MAP2K7 and LRRC8E were genotyped and tested for association with PD. In the Faroese cohort, rs7788 within SNAPC2 was significantly associated with PD, whereas rs3745383 within LRRC8E was nominally associated. No association was observed between the analysed SNPs and PD in the Danish cohorts. In the German women, we observed a nominal association between rs4804833 within MAP2K7 and PD. We present further evidence that chromosome 19p13.2 may harbour candidate genes that contribute towards the risk of developing PD. Moreover, the implication of the associated genes in other mental disorders may indicate shared genetic susceptibility between mental disorders. We show that associated variants may be sex specific, indicating the importance of carrying out a sex-specific association analysis of PD.

The influence of endophenotypic, disease-specific, and environmental variables on the expression of anxiety in pediatric epilepsy

Children and adolescents with epilepsy often show higher rates of anxiety, which carries an increased risk for reduced health-related quality of life (HRQOL). The current study assessed the role of parental psychiatric history (i.e., anxiety, depression, and/or bipolar disorder) on the rate of anxiety features in youth seen in a tertiary epilepsy clinic. Data included parental ratings on the Behavior Assessment System for Children (BASC-2) and the Quality of Life in Childhood Epilepsy (QOLCE) questionnaire for 180 children and adolescents (mean age=11.40, SD=3.98). Our results identified clinically elevated anxiety ratings in nearly half the sample (47%) with previous psychiatric history endorsed by 48% of parents. The effect of parental psychiatric history on youth anxiety was found to be significant and associated with a threefold increase in the rate of youth anxiety features. This risk increased to fourfold in refractory epilepsy, and the impact of family psychiatric history is greater in adolescent females and in families that report higher levels of stress. In those families who reported no psychiatric history, anxiety was best predicted by epilepsy-specific factors above and beyond sociodemographic factors. Parental psychiatric history was also identified as a significant risk factor for diminished patient HRQOL, even after accounting for seizure control. These findings highlight the impact of family and epilepsy factors on psychological functioning and offer further support for the strong relationship between parental adjustment and child outcome in pediatric epilepsy.

A Preliminary Genome-Wide Association Study of Pain-Related Fear: Implications for Orofacial Pain

Background

Acute and chronic orofacial pain can significantly impact overall health and functioning. Associations between fear of pain and the experience of orofacial pain are well-documented, and environmental, behavioral, and cognitive components of fear of pain have been elucidated. Little is known, however, regarding the specific genes contributing to fear of pain.

Methods

A genome-wide association study (GWAS; N = 990) was performed to identify plausible genes that may predispose individuals to various levels of fear of pain. The total score and three subscales (fear of minor, severe, and medical/dental pain) of the Fear of Pain Questionnaire-9 (FPQ-9) were modeled in a variance components modeling framework to test for genetic association with 8.5 M genetic variants across the genome, while adjusting for sex, age, education, and income.

Results

Three genetic loci were significantly associated with fear of minor pain (8q24.13, 8p21.2, and 6q26; p < 5 × 10⁻⁸ for all) near the genes TMEM65, NEFM, NEFL, AGPAT4, and PARK2. Other suggestive loci were found for the fear of pain total score and each of the FPQ-9 subscales.

Conclusions

Multiple genes were identified as possible candidates contributing to fear of pain. The findings may have implications for understanding and treating chronic orofacial pain.

The Neurobiological Mechanisms of Generalized Anxiety Disorder and Chronic Stress

Two classification systems are now at the forefront of clinical psychiatric research: (1) Diagnostic and Statistical Manual, Fifth Edition and (2) the National Institutes of Mental Health Research Domain Criteria. Herein, we propose that these two classification systems are complementary rather than mutually exclusive, and when combined provide important information for understanding aspects of the pathophysiology related to Generalized Anxiety Disorder (GAD). The neurobiological literature for GAD and one relevant research domain criteria component, sustained threat, are reviewed from multiple units of analysis (genetic, neuroimaging, neuroendocrine, and psychophysiological). It is hypothesized that generating a comprehensive, biologically based understanding of the relationship between GAD, sustained threat, and the measureable units of analysis will provide information critical to design the most effective treatments.

Strain and sex based characterization of behavioral expressions in non-induced compulsive-like mice

There is currently a lack of understanding how genetic background and sex differences attribute to the heterogeneity of obsessive-compulsive disorder (OCD). An animal model of compulsive-like behaviors has been developed through bidirectional selection of house mice (Mus musculus) for high (big cotton nests; BIG mice) and low levels (small nests; SMALL mice) of nest-building behavior. The BIG male strains have predictive and face validity as a spontaneous animal model of OCD. Here, we evaluated compulsive-, anxiety-, cognitive-, and depression-like behaviors among male and proestrus female replicate strains each of BIG (BIG1, BIG2) and SMALL (SML1, SML2) nest-builders, and randomly-bred Controls (C1, C2). BIG1 and BIG2 males and females had higher nesting scores when compared to SMALL and Control strains. Male BIG1 and BIG2 strains showed more compulsive-like nesting than BIG1 and BIG2 proestrus females, which was not observed among the other strains. Nesting scores were also different between BIG replicate male strains. A similar pattern was observed in the compulsive-like marble burying behavior with BIG strains burying more marbles than SMALL and Control strains. Significant replicate and sex differences were also observed in marble burying among the BIG strains. The open field test revealed replicate effects while the BIG strains showed less anxiety-like behavior in the elevated plus maze test compared to the SMALL strains. For novel object recognition only the Control strains showed replicate and sex differences. In the depression-like forced swim test proestrus females demonstrated less depression-like behavior than males. BIG and SMALL nest-building strains had a higher corticosterone stress response than the Control strains. Together these results indicate a strong interplay of genetic background and sex in influencing expression of behaviors in our compulsive-like mouse model. These results are in congruence with the clinical heterogeneity of OCD.

Meta-analysis of genome-wide association studies of anxiety disorders

Anxiety disorders (ADs), namely generalized AD, panic disorder and phobias, are common, etiologically complex conditions with a partially genetic basis. Despite differing on diagnostic definitions based on clinical presentation, ADs likely represent various expressions of an underlying common diathesis of abnormal regulation of basic threat-response systems. We conducted genome-wide association analyses in nine samples of European ancestry from seven large, independent studies. To identify genetic variants contributing to genetic susceptibility shared across interview-generated DSM-based ADs, we applied two phenotypic approaches: (1) comparisons between categorical AD cases and supernormal controls, and (2) quantitative phenotypic factor scores (FS) derived from a multivariate analysis combining information across the clinical phenotypes. We used logistic and linear regression, respectively, to analyze the association between these phenotypes and genome-wide single nucleotide polymorphisms. Meta-analysis for each phenotype combined results across the nine samples for over 18 000 unrelated individuals. Each meta-analysis identified a different genome-wide significant region, with the following markers showing the strongest association: for case-control contrasts, rs1709393 located in an uncharacterized non-coding RNA locus on chromosomal band 3q12.3 (P=1.65 × 10(-8)); for FS, rs1067327 within CAMKMT encoding the calmodulin-lysine N-methyltransferase on chromosomal band 2p21 (P=2.86 × 10(-9)). Independent replication and further exploration of these findings are needed to more fully understand the role of these variants in risk and expression of ADs.

Genetical Genomics of Behavior: A Novel Chicken Genomic Model for Anxiety Behavior

The identification of genetic variants responsible for behavioral variation is an enduring goal in biology, with wide-scale ramifications, ranging from medical research to evolutionary theory on personality syndromes. Here, we use for the first time a large-scale genetical genomics analysis in the brains of chickens to identify genes affecting anxiety as measured by an open field test. We combine quantitative trait locus (QTL) analysis in 572 individuals and expression QTL (eQTL) analysis in 129 individuals from an advanced intercross between domestic chickens and Red Junglefowl. We identify 10 putative quantitative trait genes affecting anxiety behavior. These genes were tested for an association in the mouse Heterogeneous Stock anxiety (open field) data set and human GWAS data sets for bipolar disorder, major depressive disorder, and schizophrenia. Although comparisons between species are complex, associations were observed for four of the candidate genes in mice and three of the candidate genes in humans. Using a multimodel approach we have therefore identified a number of putative quantitative trait genes affecting anxiety behavior, principally in chickens but also with some potentially translational effects as well. This study demonstrates that chickens are an excellent model organism for the genetic dissection of behavior.

Genome-wide significant loci for addiction and anxiety

BACKGROUND

Psychiatric comorbidity is common among individuals with addictive disorders, with patients frequently suffering from anxiety disorders. While the genetic architecture of comorbid addictive and anxiety disorders remains unclear, elucidating the genes involved could provide important insights into the underlying etiology.

METHODS

Here we examine a sample of 1284 Mexican-Americans from randomly selected extended pedigrees. Variance decomposition methods were used to examine the role of genetics in addiction phenotypes (lifetime history of alcohol dependence, drug dependence or chronic smoking) and various forms of clinically relevant anxiety. Genome-wide univariate and bivariate linkage scans were conducted to localize the chromosomal regions influencing these traits.

RESULTS

Addiction phenotypes and anxiety were shown to be heritable and univariate genome-wide linkage scans revealed significant quantitative trait loci for drug dependence (14q13.2-q21.2, LOD=3.322) and a broad anxiety phenotype (12q24.32-q24.33, LOD=2.918). Significant positive genetic correlations were observed between anxiety and each of the addiction subtypes (ρg=0.550-0.655) and further investigation with bivariate linkage analyses identified significant pleiotropic signals for alcohol dependence-anxiety (9q33.1-q33.2, LOD=3.054) and drug dependence-anxiety (18p11.23-p11.22, LOD=3.425).

CONCLUSIONS

This study confirms the shared genetic underpinnings of addiction and anxiety and identifies genomic loci involved in the etiology of these comorbid disorders. The linkage signal for anxiety on 12q24 spans the location of TMEM132D, an emerging gene of interest from previous GWAS of anxiety traits, whilst the bivariate linkage signal identified for anxiety-alcohol on 9q33 peak coincides with a region where rare CNVs have been associated with psychiatric disorders. Other signals identified implicate novel regions of the genome in addiction genetics.

Don't worry; be informed about the epigenetics of anxiety

Epigenetic processes regulate gene expression independent of the DNA sequence and are increasingly being investigated as contributors to the development of behavioral disorders. Environmental insults, such as stress, diet, or toxin exposure, can affect epigenetic mechanisms, including chromatin remodeling, DNA methylation, and non-coding RNAs that, in turn, alter the organism's phenotype. In this review, we examine the literature, derived at both the preclinical (animal) and clinical (human) levels, on epigenetic alterations associated with anxiety disorders. Using animal models of anxiety, researchers have identified epigenetic changes in several limbic and cortical brain regions known to be involved in stress and emotion responses. Environmental manipulations have been imposed prior to conception, during prenatal or early postnatal periods, and at juvenile and adult ages. Time of perturbation differentially affects the epigenome and many changes are brain region-specific. Although some sex-dependent effects are reported in animal studies, more research employing both sexes is needed particularly given that females exhibit a disproportionate number of anxiety disorders. The human literature is in its infancy but does reveal some epigenetic associations with anxiety behaviors and disorders. In particular, effects in monoaminergic systems are seen in line with evidence from etiological and treatment research. Further, there is evidence that epigenetic changes may be inherited to affect subsequent generations. We speculate on how epigenetic processes may interact with genetic contributions to inform prevention and treatment strategies for those who are at risk for or have anxiety disorders.

Cortical and subcortical gamma amino acid butyric acid deficits in anxiety and stress disorders: Clinical implications

Anxiety and stress disorders are a major public health issue. However, their pathophysiology is still unclear. The gamma amino acid butyric acid (GABA) neurochemical system has been strongly implicated in their pathogenesis and treatment by numerous preclinical and clinical studies, the most recent of which have been highlighted and critical review in this paper. Changes in cortical GABA appear related to normal personality styles and responses to stress. While there is accumulating animal and human neuroimaging evidence of cortical and subcortical GABA deficits across a number of anxiety conditions, a clear pattern of findings in specific brain regions for a given disorder is yet to emerge. Neuropsychiatric conditions with anxiety as a clinical feature may have GABA deficits as an underlying feature. Different classes of anxiolytic therapies support GABA function, and this may be an area in which newer GABA neuroimaging techniques could soon offer more personalized therapy. Novel GABAergic pharmacotherapies in development offer potential improvements over current therapies in reducing sedative and physiologic dependency effects, while offering rapid anxiolysis.

Longitudinal associations between social anxiety disorder and avoidant personality disorder: A twin study

Social anxiety disorder (SAD) and avoidant personality disorder (AvPD) are frequently co-occurring psychiatric disorders with symptomatology related to fear of social situations. It is uncertain to what degree the 2 disorders reflect the same genetic and environmental risk factors. The current study addresses the stability and co-occurrence of SAD and AvPD, the factor structure of the diagnostic criteria, and genetic and environmental factors underlying the disorders at 2 time points. SAD and AvPD were assessed in 1,761 young adult female twins at baseline and 1,471 of these approximately 10 years later. Biometric models were fitted to dimensional representations of SAD and AvPD. SAD and AvPD were moderately and approximately equally stable from young to middle adulthood, with increasing co-occurrence driven by environmental factors. At the first wave, approximately 1 in 3 individuals with AvPD had SAD, increasing to 1 in 2 at follow-up. The diagnostic criteria for SAD and AvPD had a two-factor structure with low cross-loadings. The relationship between SAD and AvPD was best accounted for by a model with separate, although highly correlated (r = .76), and highly heritable (.66 and .71) risk factors for each disorder. Their genetic and environmental components correlated .84 and .59, respectively. The finding of partially distinct risk factors indicates qualitative differences in the etiology of SAD and AvPD. Genetic factors represented the strongest time-invariant influences, whereas environmental factors were most important at the specific points in time.

The Genetics of Stress-Related Disorders: PTSD, Depression, and Anxiety Disorders

Research into the causes of psychopathology has largely focused on two broad etiologic factors: genetic vulnerability and environmental stressors. An important role for familial/heritable factors in the etiology of a broad range of psychiatric disorders was established well before the modern era of genomic research. This review focuses on the genetic basis of three disorder categories-posttraumatic stress disorder (PTSD), major depressive disorder (MDD), and the anxiety disorders-for which environmental stressors and stress responses are understood to be central to pathogenesis. Each of these disorders aggregates in families and is moderately heritable. More recently, molecular genetic approaches, including genome-wide studies of genetic variation, have been applied to identify specific risk variants. In this review, I summarize evidence for genetic contributions to PTSD, MDD, and the anxiety disorders including genetic epidemiology, the role of common genetic variation, the role of rare and structural variation, and the role of gene-environment interaction. Available data suggest that stress-related disorders are highly complex and polygenic and, despite substantial progress in other areas of psychiatric genetics, few risk loci have been identified for these disorders. Progress in this area will likely require analysis of much larger sample sizes than have been reported to date. The phenotypic complexity and genetic overlap among these disorders present further challenges. The review concludes with a discussion of prospects for clinical translation of genetic findings and future directions for research.

Shared Genetic Factors of Anxiety and Depression Symptoms in a Brazilian Family-Based Cohort, the Baependi Heart Study

To investigate the phenotypic and genetic overlap between anxiety and depression symptoms in an admixed population from extended family pedigrees. Participants (n = 1,375) were recruited from a cohort of 93 families (mean age±SD 42±16.3, 57% female) in the rural town of Baependi, Brazil. The Hospital Anxiety and Depression Scale (HADS) was used to assess depression and anxiety symptoms. Heritability estimates were obtained by an adjusted variance component model. Bivariate analyses were performed to obtain the partition of the covariance of anxiety and depression into genetic and environmental components, and to calculate the genetic contribution modulating both sets of symptoms. Anxiety and depression scores were 7.49±4.01 and 5.70±3.82, respectively. Mean scores were affected by age and were significantly higher in women. Heritability for depression and anxiety, corrected for age and sex, were 0.30 and 0.32, respectively. Significant genetic correlations (ρ_g = 0.81) were found between anxiety and depression scores; thus, nearly 66% of the total genetic variance in one set of symptoms was shared with the other set. Our results provided strong evidence for a genetic overlap between anxiety and depression symptoms, which has relevance for our understanding of the biological basis of these constructs and could be exploited in genome-wide association studies.

Nature and psychological management of anxiety disorders in youth

Anxiety disorders affect around 5% of the paediatric population at any given time and are associated with high social and personal impact. These disorders typically begin early in life, and children with anxiety disorders are at increased risk for a variety of later difficulties across the life-span. Although causes of anxiety in childhood are not fully understood, there is a strong heritable component. Additional risk factors include temperament, parent psychopathology, parent handling and peer interactions. Psychological treatments have demonstrated good efficacy with around 60% of anxious youth being in diagnostic remission immediately following treatment and a further 10% remitting over the following months. Because young people with anxiety disorders are among the least likely to seek appropriate help, paediatricians are in a unique position to identify anxious young people, educate families and recommend appropriate intervention.

Anxiety disorders and anxiety-related traits and serotonin transporter gene-linked polymorphic region (5-HTTLPR) in adolescents: case-control and trio studies

The role of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) in anxiety disorder and anxiety-related traits is controversial. Besides this study, few studies have evaluated the triallelic genotype in adolescents. The aim of this study was to investigate whether anxiety disorders and anxiety-related traits are associated with 5-HTTLPR (biallelic and triallelic) in adolescents, integrating both case-control-based and family-based designs in a community sample. This is a cross-sectional community study of 504 individuals and their families: 225 adolescents (129 adolescents with anxiety disorder and 96 controls) and their biological families. We assessed psychiatric diagnosis using the Kiddie Schedule for Affective Disorders and Schizophrenia. The Temperament and Character Inventory and the Resnick Behavioral Inhibition Scale were used to evaluate harm avoidance and behavioral inhibition. DNA was extracted from saliva and genotyped, including biallelic and triallelic 5-HTTLPR classification, by PCR-RFLP followed by agarose gel electrophoresis. We were not able to find any associations between 5-HTTLPR and anxiety-related phenotypes in both case-control and trio analyses. Further investigation and meta-analytic studies are needed to better clarify the inconsistent results with regard to the association between 5-HTTLPR and anxiety-related phenotypes in adolescents.

Genome-wide and gene-based association studies of anxiety disorders in European and African American samples

Anxiety disorders (ADs) are common mental disorders caused by a combination of genetic and environmental factors. Since ADs are highly comorbid with each other, partially due to shared genetic basis, studying AD phenotypes in a coordinated manner may be a powerful strategy for identifying potential genetic loci for ADs. To detect these loci, we performed genome-wide association studies (GWAS) of ADs. In addition, as a complementary approach to single-locus analysis, we also conducted gene- and pathway-based analyses. GWAS data were derived from the control sample of the Molecular Genetics of Schizophrenia (MGS) project (2,540 European American and 849 African American subjects) genotyped on the Affymetrix GeneChip 6.0 array. We applied two phenotypic approaches: (1) categorical case-control comparisons (CC) based upon psychiatric diagnoses, and (2) quantitative phenotypic factor scores (FS) derived from a multivariate analysis combining information across the clinical phenotypes. Linear and logistic models were used to analyse the association with ADs using FS and CC traits, respectively. At the single locus level, no genome-wide significant association was found. A trans-population gene-based meta-analysis across both ethnic subsamples using FS identified three genes (MFAP3L on 4q32.3, NDUFAB1 and PALB2 on 16p12) with genome-wide significance (false discovery rate (FDR] <5%). At the pathway level, several terms such as transcription regulation, cytokine binding, and developmental process were significantly enriched in ADs (FDR <5%). Our approaches studying ADs as quantitative traits and utilizing the full GWAS data may be useful in identifying susceptibility genes and pathways for ADs.

Genetic and environmental causes of variation in adolescent anxiety symptoms: a multiple-rater twin study

Heritability estimates for adolescent anxiety vary across studies, partly depending on who is rating the symptoms. The goal of our study was to estimate genetic and environmental influences using a multi-informant design with responses from a population-based sample of adolescent twins, their mothers and their fathers (N=1394 families). Results from multivariate biometrical modeling indicated quantitative, but no qualitative sex differences in etiology. The best fitting model was an AE Common Pathway model, defining anxiety as a latent factor common to all informants. This model offers error free estimates of genetic and environmental influences explaining the latent factor variance. Variation in the latent factor was highly genetic, with heritability estimates of 65% for boys and 74% for girls. Non-shared environmental effects explained the remaining variance. In addition, there were significant rater-specific genetic and environmental effects for both sexes. The observed rater differences underline the importance of using several informants when studying adolescent anxiety.

Interactions between diabetes and anxiety and depression: implications for treatment

Anxiety or depression may be a risk factor for the development of diabetes. This relationship may occur through a combination of genetic predispositions; epigenetic contingencies; exacerbating conditions such as metabolic syndrome (a precursor to diabetes); and other serious medical conditions. Medications used to treat anxiety and depression have significant side effects, such as weight gain, further increasing the possibility of developing diabetes. These components combine, interact, and reassemble to create a precarious system for persons with, or predisposed to, diabetes. Clinicians must be aware of these interrelationships to adequately treat the disease.

Pediatric anxiety disorders: from neuroscience to evidence-based clinical practice

The objective of this narrative review of the literature is to describe the epidemiology, etiology, pathophysiology, diagnosis, and treatment of pediatric anxiety disorders. We aim to guide clinicians in understanding the biology of anxiety disorders and to provide general guidelines for the proper diagnoses and treatment of these conditions early in life. Anxiety disorders are prevalent, associated with a number of negative life outcomes, and currently under-recognized and under-treated. The etiology involves both genes and environmental influences modifying the neural substrate in a complex interplay. Research on pathophysiology is still in its infancy, but some brain regions, such as the amygdala and the prefrontal cortex, have been implicated in fear and anxiety. Current practice is to establish diagnosis based purely on clinical features, derived from clinical interviews with the child, parents, and teachers. Treatment is effective using medication, cognitive behavioral therapy, or a combination of both. An introduction to the neuroscience behind anxiety disorders combined with an evidence-based approach may help clinicians to understand these disorders and treat them properly in childhood.

Low-anxiety rat phenotypes can be further reduced through genetic intervention

BACKGROUND

A previous study using an intercross between the inbred rat strains Lewis (LEW) and Spontaneously Hypertensive Rats (SHR) identified a locus on chromosome 4, named Anxrr16, influencing an experimental index of anxiety and showing a transgressive effect, with alleles from the LEW strain (more anxious) decreasing rather than increasing anxiety.

OBJECTIVE

To confirm the location and isolate the effect of a rat genome region named Anxrr16 through a planned genomic recombination strategy, where the target locus in SHR rats was replaced with LEW genetic material.

METHODS

A new congenic strain, named SHR.LEW-Anxrr16 (SLA16), was developed from a cross between LEW (donor) and SHR (receptor) rats and then evaluated in several anxiety-related tests. The activity and attention levels of the new strain were also evaluated, since hyperactivity was observed during its construction and because SHR is a model of attention deficit hyperactivity disorder.

RESULTS

Significant effects of Anxrr16 were found for open field central locomotion, as well as for other indices of anxiety from the light/dark box, triple test and T-maze. In all cases, the low-anxiety levels of SHR rats were further reduced by the insertion of LEW alleles. Differences in locomotor activity were found only in unfamiliar (hence stressful) environments and no genetic effects were observed in indices of attention.

CONCLUSION

The SLA16 strain can help in the identification of the molecular pathways involved in experimental anxiety and it demonstrates how apparently extreme phenotypes sometimes hide major opposite-acting genes.

The α-endomannosidase gene (MANEA) is associated with panic disorder and social anxiety disorder

Unbiased genome-wide approaches can provide novel insights into the biological pathways that are important for human behavior and psychiatric disorder risk. The association of α-endomannosidase gene (MANEA) variants and cocaine-induced paranoia (CIP) was initially described in a study that used a whole-genome approach. Behavioral effects have been reported for other mannosidase genes, but MANEA function in humans and the clinical potential of the previous findings remain unclear. We hypothesized that MANEA would be associated with psychiatric phenotypes unrelated to cocaine use. We used a multi-stage association study approach starting with four psychiatric disorders to show an association between a MANEA single-nucleotide polymorphism (SNP; rs1133503) and anxiety disorders. In the first study of 2073 European American (EA) and 2459 African American subjects mostly with comorbid drug or alcohol dependence, we observed an association in EAs of rs1133503 with panic disorder (PD) (191 PD cases, odds ratio (OR)=1.7 (95% confidence interval (CI): 1.22-2.41), P=0.002). We replicated this finding in an independent sample of 142 PD cases (OR =1.53 (95% CI: 1.00-2.31), P=0.043) and extended it in an independent sample of 131 generalized social anxiety disorder cases (OR=2.15 (95% CI: 1.27-3.64), P=0.004). MANEA alleles and genotypes were also associated with gene expression differences in whole blood cells. Using publically available data, we observed a consistent effect on expression in brain tissue. We conclude that pathways involving α-endomannosidase warrant further investigation in relation to anxiety disorders.

Attachment and parenting in adult patients with anxiety disorders

Background:

The literature suggests that dysfunctional parenting and insecure attachment may increase risk of anxiety-related psychopathology. This study aimed at testing the association between anxiety disorders, attachment insecurity and dysfunctional parenting while controlling for factors usually not controlled for in previous studies, such as gender, age, and being ill.

Methods:

A sample of 32 non-psychotic inpatients with SCID-I diagnosis of an anxiety disorder, either alone or in comorbidity, was compared with two age- and sex-matched control groups consisting of 32 non-clinical participants and 32 in-patients with drug-resistant epilepsy. Study measures included the Experience in Close Relationships questionnaire (ECR) and the Parental Bonding Instrument (PBI).

Results:

The patients with anxiety disorders scored significantly higher on attachment-related anxiety and avoidance than patients with drug-resistant epilepsy and non-clinical participants. These findings were independent of comorbidity for mood disorders. ECR scores did not differ among diagnostic subgroups (generalized anxiety disorder, panic disorder, other anxiety disorders). Patients with anxiety disorders scored significantly lower on PBI mother’s care and borderline significantly lower on PBI father's care than patients with drug-resistant epilepsy.

Conclusions:

Although limitations such as the relatively small sample size and the cross-sectional nature suggest caution in interpreting these findings, they are consistent with the few previous adult studies performed on this topic and corroborate Bowlby's seminal hypothesis of a link between negative attachment-related experiences, attachment insecurity, and clinical anxiety. Attachment theory provides a useful theoretical framework for integrating research findings from several fields concerning the development of anxiety disorders and for planning therapeutic interventions.

Disorders and borders: psychiatric genetics and nosology

Over the past century, the definition and classification of psychiatric disorders has evolved through a combination of historical trends, clinical observations, and empirical research. The current nosology, instantiated in the DSM-5 and ICD-10, rests on descriptive criteria agreed upon by a consensus of experts. While the development of explicit criteria has enhanced the reliability of diagnosis, the validity of the current diagnostic categories has been the subject of debate and controversy. Genetic studies have long been regarded as a key resource for validating the boundaries among diagnostic categories. Genetic epidemiologic studies have documented the familiality and heritability of clinically defined psychiatric disorders and molecular genetic studies have begun to identify specific susceptibility variants. At the same time, there is growing evidence from family, twin and genomic studies that genetic influences on psychiatric disorders transcend clinical boundaries. Here I review this evidence for cross-disorder genetic effects and discuss the implications of these findings for psychiatric nosology. Psychiatric genetic research can inform a bottom-up reappraisal of psychopathology that may help the field move beyond a purely descriptive classification and toward an etiology-based nosology.

The role of the serotonergic and GABA system in translational approaches in drug discovery for anxiety disorders

There is ample evidence that genetic factors play an important role in anxiety disorders. In support, human genome-wide association studies have implicated several novel candidate genes. However, illumination of such genetic factors involved in anxiety disorders has not resulted in novel drugs over the past decades. A complicating factor is the heterogeneous classification of anxiety disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) and diverging operationalization of anxiety used in preclinical and clinical studies. Currently, there is an increasing focus on the gene × environment (G × E) interaction in anxiety as genes do not operate in isolation and environmental factors have been found to significantly contribute to the development of anxiety disorders in at-risk individuals. Nevertheless, extensive research on G × E mechanisms in anxiety has not resulted in major breakthroughs in drug discovery. Modification of individual genes in rodent models has enabled the specific study of anxiety in preclinical studies. In this context, two extensively studied neurotransmitters involved in anxiety are the gamma-aminobutyric acid (GABA) and 5-HT (5-hydroxytryptamine) system. In this review, we illustrate the complex interplay between genes and environment in anxiety processes by reviewing preclinical and clinical studies on the serotonin transporter (5-HTT), 5-HT1A receptor, 5-HT2 receptor, and GABAA receptor. Even though targets from the serotonin and GABA system have yielded drugs with known anxiolytic efficacy, the relation between the genetic background of these targets and anxiety symptoms and development of anxiety disorders is largely unknown. The aim of this review is to show the vast complexity of genetic and environmental factors in anxiety disorders. In light of the difficulty with which common genetic variants are identified in anxiety disorders, animal models with translational validity may aid in elucidating the neurobiological background of these genes and their possible role in anxiety. We argue that, in addition to human genetic studies, translational models are essential to map anxiety-related genes and to enhance our understanding of anxiety disorders in order to develop potentially novel treatment strategies.

The association between parental history of diagnosed mood/anxiety disorders and psychiatric symptoms and disorders in young adult offspring

BACKGROUND

Parental history of mood or anxiety disorders is one of the strongest and most consistent risk factors for the development of these disorders in offspring. Gaps remain however in our knowledge of whether maternal or paternal disorders are more strongly associated with offspring disorders, and whether the association exists in non-clinical samples. This study uses a large population-based sample to test if maternal or paternal history of mood and/or anxiety disorders increases the risk of mood and/or anxiety disorders, or symptoms of specific anxiety disorders, in offspring.

METHODS

Data were drawn from the Nicotine Dependence in Teens Study, a prospective cohort investigation of 1293 grade 7 students. Data on mental health outcomes were collected in mailed self-report questionnaires when participants were aged 20.4 (0.7) years on average. Parental data were collected in mailed self-report questionnaires. This current analysis pertains to 564 participants with maternal and/or paternal data. The association between maternal and paternal history and each of diagnosed anxiety disorder, diagnosed mood disorder, and symptoms of specific anxiety disorders in offspring was studied in multivariate logistic regression.

RESULTS

A higher proportion of mothers than fathers had a diagnosed mood/anxiety disorder (23% versus 12%). Similarly, 14% of female offspring had a diagnosed mood/anxiety disorder, compared to 6% of male offspring. The adjusted odds ratio (95% confidence interval) for maternal history was 2.2 (1.1, 4.5) for diagnosed mood disorders, 4.0 (2.1, 7.8) for diagnosed anxiety disorders, and 2.2 (1.2, 4.0) for social phobia symptoms. Paternal history was not associated with any of the mental health outcomes in offspring.

CONCLUSION

Maternal, but not paternal mood/anxiety disorders were associated with diagnosed psychiatric disorders, as well as symptoms of specific anxiety disorders, in offspring. Efforts to detect mood and anxiety disorders in offspring with a maternal history should be encouraged.

Meta-analysis of genome-wide association studies for panic disorder in the Japanese population

Panic disorder (PD) is a moderately heritable anxiety disorder whose pathogenesis is not well understood. Due to the lack of power in previous association studies, genes that are truly associated with PD might not be detected. In this study, we conducted a genome-wide association study (GWAS) in two independent data sets using the Affymetrix Mapping 500K Array or Genome-Wide Human SNP Array 6.0. We obtained imputed genotypes for each GWAS and performed a meta-analysis of two GWAS data sets (718 cases and 1717 controls). For follow-up, 12 single-nucleotide polymorphisms (SNPs) were tested in 329 cases and 861 controls. Gene ontology enrichment and candidate gene analyses were conducted using the GWAS or meta-analysis results. We also applied the polygenic score analysis to our two GWAS samples to test the hypothesis of polygenic components contributing to PD. Although genome-wide significant SNPs were not detected in either of the GWAS nor the meta-analysis, suggestive associations were observed in several loci such as BDKRB2 (P=1.3 × 10(-5), odds ratio=1.31). Among previous candidate genes, supportive evidence for association of NPY5R with PD was obtained (gene-wise corrected P=6.4 × 10(-4)). Polygenic scores calculated from weakly associated SNPs (P<0.3 and 0.4) in the discovery sample were significantly associated with PD status in the target sample in both directions (sample I to sample II and vice versa) (P<0.05). Our findings suggest that large sets of common variants of small effects collectively account for risk of PD.

Genetics of pediatric anxiety disorders

This article reviews the familiality, linkage, candidate gene, and genomewide association studies of obsessive-compulsive disorder, panic disorder, posttraumatic stress disorder, and other anxiety disorders (ie, generalized anxiety disorder, separation anxiety disorder, social phobia, and specific phobia). Studies involving children and adolescents are highlighted. Clinical and research implications are discussed.

Linkage analysis of alternative anxiety phenotypes in multiply affected panic disorder families

BACKGROUND

The choice of phenotype definitions for genetic studies of panic and phobic disorders is complicated by family, twin, and neurobiological data indicating both distinct and shared risk factors as well as heterogeneity within categories. We have previously reported a genome scan in 120 multiplex panic disorder (PD) families using a phenotype that closely adhered to the Diagnostic and Statistical Manual of Mental Disorders, 4th ed., PD definition. Here, we extend this work by carrying out exploratory linkage analyses in this same pedigree set using ten additional literature-based panic and phobia-related phenotypes that take into account aspects of these hypothesized complexities.

METHODS

Multiply affected families (>2 individuals with PD) were recruited from clinical and nonclinical sources, evaluated by a clinician-administered semistructured interview and a subsequent blind consensus best estimate procedure. Each phenotype was analyzed under dominant and recessive models using parametric two-point (homogeneity and heterogeneity), multipoint, and nonparametric methods. Empirically based permutations were used to estimate model-specific and global (across all phenotypes) P-values.

RESULTS

The highest score was a two-point lod (4.27, global P<0.08) on chromosome 13 (D13S793, 76 cM) for the phenotype 'specific or social phobia' under a recessive model and conditions of homogeneity. There was minimal support for linkage to any of the remaining nine phenotypes.

CONCLUSION

Although the interpretation of findings is limited by the sample size and the large number of phenotypes and models analyzed, these data suggest a region on chromosome 13 as a potential site for further exploration in relation to the risk for specific and social phobias.

Gender differences in associations of glutamate decarboxylase 1 gene (GAD1) variants with panic disorder

BACKGROUND

Panic disorder is common (5% prevalence) and females are twice as likely to be affected as males. The heritable component of panic disorder is estimated at 48%. Glutamic acid dehydrogenase GAD1, the key enzyme for the synthesis of the inhibitory and anxiolytic neurotransmitter GABA, is supposed to influence various mental disorders, including mood and anxiety disorders. In a recent association study in depression, which is highly comorbid with panic disorder, GAD1 risk allele associations were restricted to females.

METHODOLOGY/PRINCIPAL FINDINGS

Nineteen single nucleotide polymorphisms (SNPs) tagging the common variation in GAD1 were genotyped in two independent gender and age matched case-control samples (discovery sample n = 478; replication sample n = 584). Thirteen SNPs passed quality control and were examined for gender-specific enrichment of risk alleles associated with panic disorder by using logistic regression including a genotype×gender interaction term. The latter was found to be nominally significant for four SNPs (rs1978340, rs3762555, rs3749034, rs2241165) in the discovery sample; of note, the respective minor/risk alleles were associated with panic disorder only in females. These findings were not confirmed in the replication sample; however, the genotype×gender interaction of rs3749034 remained significant in the combined sample. Furthermore, this polymorphism showed a nominally significant association with the Agoraphobic Cognitions Questionnaire sum score.

CONCLUSIONS/SIGNIFICANCE

The present study represents the first systematic evaluation of gender-specific enrichment of risk alleles of the common SNP variation in the panic disorder candidate gene GAD1. Our tentative results provide a possible explanation for the higher susceptibility of females to panic disorder.