Genetic and environmental sources of covariation between generalized anxiety disorder and neuroticism

Molecular genetics of anxiety in mice and men

Human anxiety disorders represent one of the most common mental illnesses. They are complex diseases with both genetic and environmental factors affecting their predisposition. Since the basic neuronal mechanisms are shared across mammalian species, the same set of genes may regulate critical aspects of anxiety in humans and in lower species. In this review, we first summarize findings from human molecular genetic approaches to anxiety disorders or anxiety-related personality traits: genome-wide scans and candidate gene studies in large families or case-control cohorts. We then discuss recent studies that have used genome-wide methods in mouse strains to identify genes that regulate anxiety-like behavior. Although it has been difficult to pinpoint specific susceptibility genes for anxiety disorders, ongoing efforts to collect larger study cohorts and to develop new genetic tools should help in this task. Studies in animals have shown that novel quantitative trait locus (QTL) and functional genomics approaches might lead to the identification of regulators of anxiety in mice, and that these genes can be tested for their involvement in human anxiety disorders. Finally, breakthroughs are expected in the fine-mapping of human and mouse genetic linkage regions and in the identification of novel candidate genes using genome-wide methods in mouse models of anxiety.

Selective mutism and social anxiety disorder: all in the family?

OBJECTIVE

To examine the history of lifetime psychiatric disorders in the parents of children with selective mutism (SM) compared to parents of children in a control group.

METHOD

Seventy parent dyads (n = 140) of children with lifetime SM and 31 parent dyads (n = 62) of children without SM were interviewed with the Structured Clinical Interview for DSM-IV (IV and II) anxiety disorders, mood disorders, avoidant personality disorder, and schizoid personality disorder modules via telephone. Interviewers were blind to proband status. The NEO Personality Inventory was also administered.

RESULTS

Lifetime generalized social phobia was present in 37.0% of SM parents compared to 14.1% of control parents (chi2 = 10.98; p < .001; odds ratio 3.6, 95% confidence interval 1.6-7.9). Avoidant personality disorder was present in 17.5% of the SM parents compared to 4.7% of control parents (chi2 = 6.18; p < .05; odds ratio 4.3, 95% confidence interval 1.3-14.9). The proportion of parents with other psychiatric disorders was not different between groups. SM parents had higher neuroticism and lower openness scores on the NEO Personality Inventory than control parents.

CONCLUSIONS

These results support earlier uncontrolled findings of a familial relationship between generalized social phobia and SM.

The association of anxiety disorders and obsessive compulsive personality disorder with anorexia nervosa: evidence from a family study with discussion of nosological and neurodevelopmental implications

BACKGROUND

To investigate the association of anorexia nervosa with anxiety disorders through use of a case-control family study design.

METHOD

Lifetime prevalence of anxiety disorders and obsessive compulsive personality disorder was determined among 574 first-degree relatives of 152 probands with anorexia nervosa and compared to rates observed among 647 first-degree relatives of 181 never-ill control probands.

RESULTS

Adjusting for comorbidity of the same illness in the proband, relatives of probands with anorexia nervosa, had a significantly higher prevalence of generalized anxiety, obsessive compulsive disorder, separation anxiety disorder, social phobia, panic disorder, and obsessive compulsive personality disorder compared to relatives of never-ill control probands.

CONCLUSION

Anorexia nervosa may share familial liability factors in common with various anxiety phenotypes. In suggesting that a transmitted propensity for anxiety is a key aspect of vulnerability in anorexia nervosa, the findings point to research developments in the affective neurosciences, specifically the neurocircuitry of fear and anxiety, as a heuristic framework in which to interpret aspects of premorbid temperamental anxieties and clinical symptoms.

Significant correlation in linkage signals from genome-wide scans of schizophrenia and schizotypy

Prior family and adoption studies have suggested a genetic relationship between schizophrenia and schizotypy. However, this has never been verified using linkage methods. We therefore attempted to test for a correlation in linkage signals from genome-wide scans of schizophrenia and schizotypy. The Irish study of high-density schizophrenia families comprises 270 families with at least two members with schizophrenia or poor-outcome schizoaffective disorder (n=637). Non-psychotic relatives were assessed using the structured interview for schizotypy (n=746). A 10-cM multipoint, non-parametric, autosomal genome-wide scan of schizophrenia was performed in Merlin. A scan of a quantitative trait comprising ratings of DSM-III-R criteria for schizotypal personality disorder in non-psychotic relatives was also performed. Schizotypy logarithm of the odds (LOD) scores were regressed onto schizophrenia LOD scores at all loci, with adjustment for spatial autocorrelation. To assess empirical significance, this was also carried out using 1000 null scans of schizotypy. The number of jointly linked loci in the real data was compared to distribution of jointly linked loci in the null scans. No markers were suggestively linked to schizotypy based on strict Lander-Kruglyak criteria. Schizotypy LODs predicted schizophrenia LODs above chance expectation genome wide (empirical P=0.04). Two and four loci yielded nonparametric LOD (NPLs) >1.0 and >0.75, respectively, for both schizophrenia and schizotypy (genome-wide empirical P=0.04 and 0.02, respectively). These results suggest that at least a subset of schizophrenia susceptibility genes also affects schizotypy in non-psychotic relatives. Power may therefore be increased in molecular genetic studies of schizophrenia if they incorporate measures of schizotypy in non-psychotic relatives.

No association between the BDNF Val66Met polymorphism and mood status in a non-clinical community sample of 7389 older adults

Recent research has suggested that brain-derived neurotrophic factor (BDNF) may be implicated in the aetiology of mood-related phenotypes. Here we report an investigation of the association between a BDNF coding variant (Val66Met, rs6265) and mood status in a large non-clinical sample of men and women. We genotyped 7389 adult men and women, aged 41-80 years, selected from participants in the European Prospective Investigation into Cancer and Nutrition in Norfolk (EPIC-Norfolk, United Kingdom). Evidence of past year prevalent, lifetime and recurrent episodic major depressive disorder (MDD) and of past year prevalent and lifetime generalised anxiety disorder (GAD), defined by DSM-IV diagnostic criteria, was assessed through questionnaire together with a five-item version of the Mental Health Inventory (MHI-5). A total of 1214 (16.4%) participants reported lifetime MDD and 355 (4.8%) reported lifetime GAD. In this population based study we found no evidence to support an association between the BDNF gene Val66Met polymorphism and mood status.

A general population twin study of the CBCL/6-18 DSM-oriented scales

OBJECTIVE

To explore the contributions of genetic and environmental influences to individual variation and covariation of the Child Behavior Checklist (CBCL) DSM-oriented scales (DOS) originally proposed by Achenbach and associates in 2001.

METHOD

A classic twin study of 398 twin pairs ages 8 to 17 years belonging to the population-based Italian Twin Registry, assessed by parents using the CBCL for Ages 6 to 18 (CBCL/6-18).

RESULTS

Univariate analyses showed that compared with the classic CBCL/6-18 empirical subscales, the DOS have higher heritability (lowest 0.54 for Anxiety Problems, highest 0.71 for Conduct Problems) and simpler causal structure in that the phenotypic variance was satisfactorily explained by additive genetic and unique environmental factors only. Multivariate analyses showed that the causes of phenotypic correlation among the different DOS can be attributed to one common genetic factor and to two idiosyncratic environmental factors, each loading differently on the Internalizing (Anxiety and Affective Problems) and the Externalizing (Attention-Deficit/Hyperactivity, Oppositional Defiant, and Conduct Problems) CBCL/6-18 DOS.

CONCLUSIONS

Several common risk factors of both genetic and environmental nature can simultaneously affect a child's proneness to develop the psychopathological signs and symptoms captured by the CBCL/6-18 DOS.

Self-rated importance of religion predicts one-year outcome of patients with panic disorder

Cognitive-behavioral therapy and medication are efficacious treatments for panic disorder, but individual attributes such as coping and motivation are important determinants of treatment response. A sample of 56 patients with panic disorder, treated with group cognitive-behavioral therapy, were reassessed 6 months and 12 months after initial assessment. We studied the effect of self-rated importance of religion, perceived stress, self-esteem, mastery, and interpersonal alienation on outcome as measured by the General Severity Index of the Brief Symptom Inventory (BSI.GSI). Importance of religion was a predictor of BSI.GSI symptom improvement at 1 year. Over time, improvement was seen for the religion is very important subgroup in the BSI.GSI and Perceived Stress Scales. This study suggests that one mechanism by which high importance of religion reduces psychiatric symptoms is through reducing perceived stress.

The relationship of neuroticism and extraversion to symptoms of anxiety and depression in the general population

Few studies have investigated the relationship of the personality dimensions of neuroticism and extraversion to the symptoms of depression and anxiety in the general population. A random general population sample (ages 20-70 years), from two Finnish cities was surveyed with the Eysenck Personality Inventory (EPI), Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI). In addition, questions regarding diagnosed lifetime mental disorders, health care use for psychiatric reasons in the past 12 months, and history of mental disorders in first-degree relatives were posed. Among the 441 subjects who participated, neuroticism correlated strongly with symptoms of depression (r(s)=.71, P<.001) and anxiety (r(s)=.69, P<.001), and somewhat with self-reported lifetime mental disorder (r(s)=.30, P<.001) and health care use for psychiatric reasons in the past 12 months (r(s)=.24, P<.001). Extraversion correlated negatively with symptoms of depression (r(s)=-.47, P<.001), anxiety (r(s)=-.36, P<.001), self-reported lifetime mental disorder (r(s)=-.17, P<.001), and health care use for psychiatric reasons in the past 12 months (r(s)=-.14, P=.004). In multiple regression models, even after adjusting for gender, age, and education, BDI scores were significantly associated with neuroticism, extraversion, and age, whereas BAI scores were associated only with neuroticism. Neuroticism is strongly associated with depressive and anxiety symptoms, and intraversion is moderately associated with depressive symptoms in the urban general population. The relationship of these personality dimensions to both self-reported lifetime mental disorders and use of health services for psychiatric reasons strengthens the clinical validity of these personality dimensions.

Basic symptoms, temperament and character in adolescent psychiatric disorders

OBJECTIVE

Basic symptoms are early subtle changes in thinking, feeling and perception that are subjectively experienced and precede the onset of a psychotic illness. In adult samples, high basic symptom scores are regarded as specific risk factors for the development of schizophrenia. The aim of this study was to explore the relevance of basic symptoms of psychiatric disorders in adolescent patients with special focus on early detection of psychosis. Furthermore, the association between basic symptoms and personality traits has been investigated.

METHOD

From 89 adolescents, who were consecutive inpatients with different psychiatric disorders in 1995 and 1997, 54 were followed up 4.7 years later. Patients were examined with the Bonn Scale for the Assessment of Basic Symptoms at the time of the first presentation and follow-up. Additionally, personality traits were assessed at follow-up using the Junior Temperament and Character Inventory.

RESULTS

None of the subjects made the transition to schizophrenia, despite high baseline scores of basic symptoms at the initial assessment. Indirect minus symptoms were found to be the most valid predictor of a persisting psychiatric diagnosis. In addition, this specific category was strongly associated with the personality traits harm avoidance and self-directedness.

CONCLUSION

In adolescents, basic symptoms in association with personality traits present as a nonspecific indicator of psychopathology rather than as an indicator of vulnerability to schizophrenia.

Generalised anxiety disorder

Generalised anxiety disorder is a persistent and common disorder, in which the patient has unfocused worry and anxiety that is not connected to recent stressful events, although it can be aggravated by certain situations. This disorder is twice as common in women than it is in men. Generalised anxiety disorder is characterised by feelings of threat, restlessness, irritability, sleep disturbance, and tension, and symptoms such as palpitations, dry mouth, and sweating. These symptoms are recognised as part of the anxiety syndrome rather than independent complaints. The symptoms overlap greatly with those of other common mental disorders and we could regard the disorder as part of a spectrum of mood and related disorders rather than an independent disorder. Generalised anxiety disorder has a relapsing course, and intervention rarely results in complete resolution of symptoms, but in the short term and medium term, effective treatments include psychological therapies, such as cognitive behavioural therapy; self-help approaches based on cognitive behavioural therapy principles; and pharmacological treatments, mainly selective serotonin reuptake inhibitors.

Structure of internalising symptoms in early adulthood

BACKGROUND

Debate surrounds the underlying structure of internalising disorders including major depression, generalised anxiety disorder, phobias and panic disorders.

AIMS

To model the within-time and across-time relationships of internalising symptoms, incorporating effects from generalised internalising and disorder-specific components of continuity.

METHOD

Data were gathered from a 25-year longitudinal study of a birth cohort of 953 New Zealand children. Outcome measures included DSM-IV symptom scores for major depression, generalised anxiety disorder, phobia and panic disorder at the ages of 18, 21 and 25 years.

RESULTS

Structural equation modelling showed that, within-times, a common underlying measure of generalised internalising explained symptom score comorbidities. Across-time correlation of symptom scores was primarily accounted for by continuity over time in generalised internalising. However, for major depression and phobia there was also evidence of across-time continuity in the disorder-specific components of symptoms.

CONCLUSIONS

Internalising symptoms can be partitioned into components reflecting both a generalised tendency to internalising and disorder-specific components.

Genetic strategies for clarifying a nosology of relational distress

The Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) has made many strides but can be improved with the addition of relationship descriptions. Relational patterns may result from individual genetic risk factors and thus help to define disorders more clearly. Relationships may also mediate genetic risk factors and be useful in identifying the genetic vulnerability, or they may moderate underlying vulnerable genes so that they are less expressed. Key prototypic relationship patterns have inherent interest to humans, moderate numerous illnesses, and deserve attention in and of themselves. Similar to the use of genetic strategies in clarifying taxons of individual disorders, genetic strategies can help delineate patterns within these key relationships, their common origins, their common outcomes, and their distinctions from near-neighbor patterns.

Personality and anxiety disorders

Personality traits and most anxiety disorders are strongly related. In this article, we review existing evidence for ways in which personality traits may relate to anxiety disorders: 1) as predisposing factors, 2) as consequences, 3) as results of common etiologies, and 4) as pathoplastic factors. Based on current information, we conclude the following: 1) Personality traits such as high neuroticism, low extraversion, and personality disorder traits (particularly those from Cluster C) are at least markers of risk for certain anxiety disorders; 2) Remission from panic disorder is generally associated with partial "normalization" of personality traits; 3) Anxiety disorders in early life may influence personality development; 4) Anxiety disorders and personality traits are usefully thought of as spectra of common genetic etiologies; and 5) Extremes of personality traits indicate greater dysfunction in patients with anxiety disorders.

Association between glutamic acid decarboxylase genes and anxiety disorders, major depression, and neuroticism

Abnormalities in the gamma-aminobutyric acid (GABA) neurotransmitter system have been noted in subjects with mood and anxiety disorders. Glutamic acid decarboxylase (GAD) enzymes synthesize GABA from glutamate, and, thus, are reasonable candidate susceptibility genes for these conditions. In this study, we examined the GAD1 and GAD2 genes for their association with genetic risk across a range of internalizing disorders. We used multivariate structural equation modeling to identify common genetic risk factors for major depression, generalized anxiety disorder, panic disorder, agoraphobia, social phobia and neuroticism (N) in a sample of 9270 adult subjects from the population-based Virginia Adult Twin Study of Psychiatric and Substance Use Disorders. One member from each twin pair for whom DNA was available was selected as a case or control based on scoring at the extremes of the genetic factor extracted from the analysis. The resulting sample of 589 cases and 539 controls was entered into a two-stage association study in which candidate loci were screened in stage 1, the positive results of which were tested for replication in stage 2. Several of the six single-nucleotide polymorphisms tested in the GAD1 region demonstrated significant association in both stages, and a combined analysis in all 1128 subjects indicated that they formed a common high-risk haplotype that was significantly over-represented in cases (P=0.003) with effect size OR=1.23. Out of 14 GAD2 markers screened in stage 1, only one met the threshold criteria for follow-up in stage 2. This marker, plus three others that formed significant haplotype combinations in stage 1, did not replicate their association with the phenotype in stage 2. Subject to confirmation in an independent sample, our study suggests that variations in the GAD1 gene may contribute to individual differences in N and impact susceptibility across a range of anxiety disorders and major depression.

QT interval duration in apparently healthy men is associated with depression-related personality trait neuroticism

OBJECTIVE

High levels of neuroticism and low self-esteem are markers for vulnerability to depression, a condition associated with a higher risk of arrhythmias. The question as to whether these depression-related personality domains are related to cardiac repolarization (duration of QT interval) in apparently healthy men has been addressed in this study.

METHODS

Participants were 658 clinically healthy males who underwent a health screening programme. QT interval duration was determined in the resting 12-lead electrocardiogram using an automated analysis program. Neuroticism was assessed by the short-scale Eysenck Personality Questionnaire and self-esteem by the Rosenberg self-esteem scale.

RESULTS

Heart-rate corrected QT interval {QTc, formula of Bazett [Bazett HC. An analysis of time relations of electrocardiograms. Heart 1920;7:353-370]} progressively increased across quartiles of neuroticism ratings. By contrast, no differences in QTc were observed across different degrees of self-esteem. A multivariate regression analysis showed that neuroticism was a statistically significant, independent predictor of QTc duration.

CONCLUSION

After adjustment for potential confounders, neuroticism scores independently predicted QT interval duration in apparently healthy men. These findings highlight the possibility that higher arrhythmic risk could be present not only in patients with clinical depression but also in depression-prone, otherwise healthy individuals.

The genetic architecture of neuroticism in 3301 Dutch adolescent twins as a function of age and sex: a study from the Dutch twin register

The objective of this study was to estimate the magnitude of genetic and environmental influences to variation in adolescent neuroticism as a function of age and sex. Neuroticism was assessed using the Amsterdamse Biografische Vragenlijst (ABV): a self-report personality instrument similar in content to the Eysenck Personality Questionnaire. Genetic modeling procedures, including age as modifier, were fitted to the total sample of 3301 Dutch adolescent twins aged 12 to 17 years (mean age 15.5). Significant influences of additive genetic factors (.59, 95% confidence intervals [CI] .54-.63) and unshared environmental factors (.41, 95% CI .37-.45) were found. Our data did not support a role of shared environment. Results showed that different genes may influence variation in neuroticism between girls and boys. No interaction was found between the variance components and age. Results generally support prior findings in adults and young children that neuroticism is influenced principally by additive genetic and unique environmental factors. The magnitude of the genetic component appears higher in the present sample of adolescents than in most studies of adults. The present study suggests that, in adolescence, different genes are expressed in boys and girls.

Identifying interactions between genes and early environment in the mouse

Interactions between genetic and early environmental factors are recognized to play a critical role in modulating susceptibility to disease, particularly mental illness. In order to better understand such mechanisms at the molecular level, we have developed a screening paradigm in mice that allows us to test the ability of targeted mutations in candidate genes to modify susceptibility to the long-term effects of different maternal environment. Offspring of genetically identical F1 hybrid dams produced by reciprocal breeding of C57BL/6 and BALB/c parents show alterations in anxiety-related behavior as a consequence of their different maternal environment. Introduction of targeted mutations into these offspring via the father allows for the identification of candidate genes that alter these maternal effects. Our strategy offers several advantages over other methods to study maternal effects, including the use of genetically identical parents, the ability to identify both prenatal and postnatal effects, the straightforward introduction of mutations and its adaptability to high-throughput screening. In order to test the utility of this paradigm to screen candidate genes, we tested for gene-environment interactions involving loss-of-function mutations in the serotonin 1A receptor gene. Our studies demonstrate that early gene-environment interactions can be successfully tested in the mouse. When combined with conditional gene targeting and other molecular genetic techniques available in the mouse, this approach has the potential to identify the molecular mechanisms underlying early gene-environment effects.

Interactions between child and parent temperament and child behavior problems

OBJECTIVE

Few studies of temperament have tested goodness-of-fit theories of child behavior problems. In this study, we test the hypothesis that interactions between child and parent temperament dimensions predict levels of child psychopathology after controlling for the effects of these dimensions individually.

METHODS

Temperament and psychopathology were assessed in a total of 175 children (97 boys, 78 girls; mean age, 10.99 years; SD, 3.66 years) using composite scores from multiple informants of the Junior Temperament and Character Inventory and the Achenbach System of Empirically Based Assessment. Parent temperament was assessed using the adult version of the Temperament and Character Inventory. Statistical analyses included multiple regression procedures to assess the contribution of child-parent temperament interactions after controlling for demographic variables, other types of child psychopathology, and the individual Temperament and Character Inventory and Junior Temperament and Character Inventory dimensions.

RESULTS

Interactions between child and parent temperament dimensions predicted higher levels of externalizing, internalizing, and attention problems over and above the effects of these dimensions alone. Among others, the combination of high child novelty seeking with high maternal novelty was associated with child attention problems, whereas the combination of high child harm avoidance and high father harm avoidance was associated with increased child internalizing problems. Many child temperament dimensions also exerted significant effects independently.

CONCLUSIONS

The association between a child temperament trait and psychopathology can be dependent upon the temperament of parents. These data lend support to previous theories of the importance of goodness-of-fit.

Exploring the boundary between temperament and generalized anxiety disorder: a receiver operating characteristic analysis

Studies of individuals with an increased tendency to experience negative emotions such as fear, sadness, and anger have documented links between this temperamental trait and anxiety disorders. There exists debate, however, concerning the degree to which high levels of a temperamental trait are a necessary and/or sufficient component of a DSM diagnosis. In this study, receiver operating characteristic (ROC) analyses assessed the relations between levels of harm avoidance (HA) and generalized anxiety disorder (GAD) diagnoses in 334 children and their parents. Analyses revealed HA scores to be highly predictive of GAD diagnoses in children (AUC=.791, P<.001) and adults (AUC=.818, P<.001). However, there were many individuals with high HA scores who did not qualify for a GAD diagnosis. These findings suggest that while there are strong associations between HA and GAD, high levels of HA are neither necessary nor sufficient in the formation of clinically significant anxiety symptoms.

New approaches to the genetic analysis of neuroticism and anxiety

The completion of the human genome project and the complementary genome projects for other species has broadened the scope for novel bioinformatic approaches to quantitative trait locus (QTL) identification. A key issue for quantitative trait nucleotide (QTN) identification is progressing from a large QTL peak, spanning perhaps 50 cM and many hundreds of genes, to a gene or nucleotide variant which is responsible for that QTL effect. The complementary use of mouse models to dissect large syntenic loci in humans is a powerful method for reducing QTL intervals to the order of 1 Mb. This paper presents an overview of the approaches used in our laboratory to ultra-fine map QTLs for anxiety-related traits, and to identify quantitative trait genes (QTG). As new genetic techniques and statistical approaches arise, we are getting closer to identifying those long sought after QTNs.