Genetic influences on anxiety in children: what we've learned and where we're heading

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.

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.

Fear acquisition and extinction in offspring of mothers with anxiety and depressive disorders

Maternal anxiety and depression are significant risk factors for the development of these disorders in offspring. The pathways through which risk is conferred remain unclear. This study examined fear acquisition and extinction in 26 children at high risk for emotional disorders by virtue of maternal psychopathology (n=14 with a mother with a principal anxiety disorder and n=12 with a mother with a principal unipolar depressive disorder) and 31 low risk controls using a discriminative Pavlovian conditioning procedure. Participants, aged between 7 and 14 years, completed 16 trials of discriminative conditioning of two geometric figures, with (CS+) and without (CS-) an aversive tone (US), followed by 8 extinction trials (4×CS+, 4×CS-). In the context of comparable discriminative conditioning, children of anxious mothers showed larger skin conductance responses during extinction to the CS+ compared to the CS-, and to both CSs from the first to the second block of extinction trials, in comparison with low risk controls. Compared to low risk controls, children of depressed mothers showed smaller skin conductance responses to the CS+ than the CS- during acquisition. These findings suggest distinct psychophysiological premorbid risk markers in offspring of anxious and depressed mothers.

Child anxiety and parenting in England and Italy: the moderating role of maternal warmth

BACKGROUND

Parenting factors have been implicated in the aetiology and maintenance of child anxiety. Most research has been correlational with little experimental or longitudinal work. Cross-cultural comparison could be illuminating. A comparison of Italian and British children and their mothers was conducted.

METHODS

A sample of 8- to 10-year old children, 60 Italian and 49 English, completed the Spence Child Anxiety Scale. Mothers also completed two questionnaires of parenting: the Skills of Daily Living Checklist (assessing maternal autonomy granting) and the Parent-Child Interaction Questionnaire (assessing maternal intrusiveness). Parenting was assessed in two video-recorded blindly rated mother-child interaction tasks, the 'belt-buckling tasks and the 'etch-a-sketch', providing objective indices of overcontrol, warmth, lack of autonomy granting, and overprotection.

RESULTS

There were no differences between the children in overall anxiety and specific forms of anxiety. Parenting, however, was markedly different for the two countries. Compared to English mothers, on the two questionnaires, Italian mothers were significantly less autonomy granting and more intrusive; and in terms of the observed indices, a significantly greater proportion of the Italian mothers displayed a high level of both overprotection and overcontrol, and a low level of autonomy granting. Notably, Italian mothers evidenced significantly more warmth than English mothers; and maternal warmth was found to moderate the impact of self-reported maternal intrusiveness on the level of both overall child anxiety and the level of child separation anxiety; and it also moderated the relationship between both observed maternal intrusiveness and overall child anxiety and observed maternal overprotectiveness and child separation anxiety.

CONCLUSIONS

Although, compared to the British mothers, the Italian mothers were more likely to evidence high levels of parenting behaviours previously found to be anxiogenic, the high levels of warmth displayed by these mothers to their children appears to have neutralised the adverse impact of these behaviours.

Three-and-a-half-factor model? The genetic and environmental structure of the CBCL/6-18 internalizing grouping

In the present article, multivariate genetic item analyses were employed to address questions regarding the ontology and the genetic and environmental etiology of the Anxious/Depressed, Withdrawn, and Somatic Complaints syndrome dimensions of the Internalizing grouping of the Child Behavior Checklist/6-18 (CBCL/6-18). Using common and independent pathway genetic factor modeling, it was examined whether these syndrome dimensions can be ascribed a realist ontology. Subsequently, the structures of the genetic and environmental influences giving rise to the observed symptom covariation were examined. Maternal ratings of a population-based sample of 17,511 Dutch twins of mean age 7.4 (SD = 0.4) on the items of the Internalizing grouping of the Dutch CBCL/6-18 were analyzed. Applications of common and independent pathway modeling demonstrated that the Internalizing syndrome dimensions may be better understood as a composite of unconstrained genetic and environmental influences than as causally relevant entities generating the observed symptom covariation. Furthermore, the results indicate a common genetic basis for anxiety, depression, and withdrawn behavior, with the distinction between these syndromes being driven by the individual-specific environment. Implications for the substantive interpretation of these syndrome dimensions are discussed.

Exploring anxiety symptoms in a large-scale twin study of children with autism spectrum disorders, their co-twins and controls

BACKGROUND

Although many children with autism spectrum disorders (ASDs) experience difficulties with anxiety,the manifestation of these difficulties remains unresolved. The current study assessed anxiety in a large population based twin sample, aged 10–15 years. Phenotypic analyses were used to explore anxiety symptoms in children with ASDs, their unaffected co-twins and a control sample.

METHODS

Participants included 146 families from the Twins Early Development Study (TEDS) where one or both children had a suspected ASD. Eighty control families were also included. The Revised Child Anxiety and Depression scale (Chorpita, Yim, Moffitt, Umemoto & Francis, 2000) was completed (self- and parent-report), along with diagnostic and cognitive tests. Children were categorized into four groups (a) ASD (b) Broader Autism Phenotype (BAP: mainly co-twins of children with ASDs, with high subclinical autistic traits) (c) unaffected co-twins (with neither ASDs nor BAP) (d) controls.

RESULTS

Children in the ASD and BAP groups scored significantly higher than controls for all parent-rated (although not child-rated) anxiety subscales.There were no significant differences between the ASD and BAP groups for any of the parent-rated anxiety subscales. Compared with controls, unaffected co-twins showed significantly heightened Social Anxiety, Generalized Anxiety,and Panic symptoms. Significant associations were observed between certain anxiety subscales and both IQ and ASD symptoms. For example, greater parent-rated Social Anxiety was associated with higher IQ and increased social and communicative impairments. Significant interrater correlations were observed for anxiety reports in children with ASDs (r = .27–.54; p < .01), their unaffected co-twins (r = .32–.63; p < .01) and controls (r = .23–.43; p < .01)suggesting that children in this sample with and without ASD symptoms were able to report on their anxiety symptoms with some accuracy.

CONCLUSIONS

These findings support previous reports of heightened anxiety in children with ASDs, at least on parent-reported measures. Unaffected co-twins of children with ASDs also showed increased anxiety, generating questions about the potential etiological overlap between ASDs and anxiety. Progress in this area now depends on more refined anxiety measurement in ASDs and continued investigation of interrater differences.

Autism spectrum traits in children with anxiety disorders

The aim of this study was to examine ASD traits in children with clinical anxiety in early development, as well as current manifestations. Parents of 42 children with an anxiety disorder (but no known diagnosis of ASD) and 42 typically developing children were interviewed using the Autism Diagnostic Interview (ADI-R). They also completed questionnaires that assessed child anxiety (SCARED-71) and children’s ASD symptoms. Results revealed that children with anxiety disorders had higher scores than typically developing children, for both ASD traits in early development as well as current ASD symptoms. A specific association was found between symptoms of Social Anxiety Disorder and ASD traits early in life. Findings are considered in terms of clinical implications, and limitations are discussed.

Mental imagery, emotion and psychopathology across child and adolescent development

Mental imagery-based interventions are receiving increasing interest for the treatment of psychological disorders in adults. This is based on evidence that mental imagery potently influences the experience of emotion in non-clinical samples, and that a number of psychological disorders are marked by syndrome-specific, distressing abnormalities in mental imagery. During childhood and adolescence, neurocognitive development impacting mental imagery processes may moderate its relationship with clinically-relevant emotional symptoms at a number of potential loci. Crucially, these changes could impact vulnerability to distressing mental imagery and the efficacy of mental imagery-based clinical interventions. This review synthesises evidence pertaining to developmental changes in the role and content of mental imagery, and in the cognitive sub-processes required to generate and sustain mental images. Subsequently, we discuss implications for understanding the developmental relationship between mental imagery, emotion and psychopathology. Translational cognitive neuroscience research investigating the content, emotional impact and neurocognitive substrates of mental imagery across development may reveal insights into trajectories of vulnerability to symptoms of a number of psychological disorders. If proper consideration is given to developmental factors, techniques based on mental imagery may be valuable as part of a treatment armoury for child and adolescent clinical populations and those at risk of emotional disorders.

Child sexual abuse in the etiology of anxiety disorders: a systematic review of reviews

There is considerable controversy about the role of child sexual abuse in the etiology of anxiety disorders. Although a growing number of research studies have been published, these have produced inconsistent results and conclusions regarding the nature of the associations between child sexual abuse and the various forms of anxiety problems as well as the potential effects of third variables, such as moderators, mediators, or confounders. This article provides a systematic review of the several reviews that have investigated the literature on the role of child sexual abuse in the etiology of anxiety disorders. Seven databases were searched, supplemented with hand search of reference lists from retrieved papers. Four meta-analyses, including 3,214,482 subjects from 171 studies, were analyzed. There is evidence that child sexual abuse is a significant, although general and nonspecific, risk factor for anxiety disorders, especially posttraumatic stress disorder, regardless of gender of the victim and severity of abuse. Additional biological or psychosocial risk factors (such as alterations in brain structure or function, information processing biases, parental anxiety disorders, family dysfunction, and other forms of child abuse) may interact with child sexual abuse or act independently to cause anxiety disorders in victims in abuse survivors. However, child sexual abuse may sometimes confer additional risk of developing anxiety disorders either as a distal and indirect cause or as a proximal and direct cause. Child sexual abuse should be considered one of the several risk factors for anxiety disorders and included in multifactorial etiological models for anxiety disorders.

Bringing a developmental perspective to anxiety genetics

Despite substantial recent advancements in psychiatric genetic research, progress in identifying the genetic basis of anxiety disorders has been limited. We review the candidate gene and genome-wide literatures in anxiety, which have made limited progress to date. We discuss several reasons for this hindered progress, including small samples sizes, heterogeneity, complicated comorbidity profiles, and blurred lines between normative and pathological anxiety. To address many of these challenges, we suggest a developmental, multivariate framework that can inform and enhance anxiety phenotypes for genetic research. We review the psychiatric and genetic epidemiological evidence that supports such a framework, including the early onset and chronic course of anxiety disorders, shared genetic risk factors among disorders both within and across time, and developmentally dynamic genetic influences. We propose three strategies for developmentally sensitive phenotyping: examination of early temperamental risk factors, use of latent factors to model underlying anxiety liability, and use of developmental trajectories as phenotypes. Expanding the range of phenotypic approaches will be important for advancing studies of the genetic architecture of anxiety disorders.

The relationships of child and parent factors with children's anxiety symptoms: parental anxious rearing as a mediator

A considerable body of research has identified various child and parent factors that contribute to and maintain anxiety symptoms in children. Yet relatively few studies have examined child factors (including threat-based cognitive bias, neuroticism, gender, puberty and age) as well as parent factors (including maternal anxiety and child-rearing style) in association with child anxiety symptoms, and the extent to which these factors serve as unique predictors of child anxiety. Moreover, research is lacking on whether parent factors such as child-rearing style, which is often targeted in early intervention and treatment programs, might mediate the association between child factors such as neuroticism, and child anxiety symptoms. In a sample of 85 children between 7 and 12 years of age with varying levels of anxiety, including those with diagnosed anxiety disorders, results showed that children were more anxious when they were reported to be more advanced in pubertal status by their parents, when they had a tendency to interpret more threat in ambiguous situations, and when they self-reported more neuroticism. Regarding parent factors, maternal self-reported trait anxiety and children's perceptions of their mother as having an anxious child-rearing style were associated with higher levels of child anxiety. Moreover, when these correlates of child anxiety were examined in a multivariate model to identify those that had direct as well as indirect associations via maternal anxious child-rearing style, child neuroticism remained as a significant and unique predictor of child anxiety that was also mediated by maternal anxious-rearing. Child neuroticism also mediated the relationship between child pubertal stage and anxiety symptoms. Results are discussed in terms of relevant theory and empirical evidence regarding the roles of both child and parent factors in the development of child anxiety.

Genetic and environmental contributions to separation anxiety: a meta-analytic approach to twin data

BACKGROUND

Separation anxiety disorder (SAD) and separation anxiety symptoms (SA) have been studied both epidemiologically and genetically; however, large between-studies discrepancies emerge relative to the role of genetic, shared-, and nonshared environmental influences on these conditions.

METHODS

Based upon available literature, 18 cohorts and 31,859 subjects belonging to twin samples in Europe, the United States, and Australia were included in three meta-analytic estimations of: the standardized variance components of etiological influences on SAD/SA, and on the effect of sex and rater.

RESULTS

Meta-analytic estimations carried out on all cohorts showed that within-family (genetic 43% and shared environmental 17%) factors explain most of individual differences for SAD/SA. Meta-heritability estimates were higher among females (.52) than males (.26), whereas nonshared environmental effects were stronger for the latter (.74) than for the former (.41). When SAD/SA was rated by parents, the shared environmental influences were higher than those obtained with self-assessment instruments (.23 versus .05), but this may reflect an age difference between subsamples.

CONCLUSIONS

A shared environmental effect is present and important in SAD/SA. Our results support at an etiological level the involvement of parents in treating SAD/SA in children, and the provision of specific strategies to parents to manage their own anxiety.

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.

Integrating etiological models of social anxiety and depression in youth: evidence for a cumulative interpersonal risk model

Models of social anxiety and depression in youth have been developed separately, and they contain similar etiological influences. Given the high comorbidity of social anxiety and depression, we examine whether the posited etiological constructs are a correlate of, or a risk factor for, social anxiety and/or depression at the symptom level and the diagnostic level. We find core risk factors of temperament, genetics, and parent psychopathology (i.e., depression and anxiety) are neither necessary nor sufficient for the development of social anxiety and/or depression. Instead, aspects of children's relationships with parents and/or peers either mediates (i.e., explains) or moderates (i.e., interacts with) these core risks being related to social anxiety and/or depression. We then examine various parent- and peer-related constructs contained in the separate models of social anxiety and depression (i.e., parent-child attachment, parenting, social skill deficits, peer acceptance and rejection, peer victimization, friendships, and loneliness). Throughout our review, we report evidence for a Cumulative Interpersonal Risk model that incorporates both core risk factors and specific interpersonal risk factors. Most studies fail to consider comorbidity, thus little is known about the specificity of these various constructs to depression and/or social anxiety. However, we identify shared, differential, and cumulative risks, correlates, consequences, and protective factors. We then put forth demonstrated pathways for the development of depression, social anxiety, and their comorbidity. Implications for understanding comorbidity are highlighted throughout, as are theoretical and research directions for developing and refining models of social anxiety, depression, and their comorbidity. Prevention and treatment implications are also noted.

Conceptual relations between anxiety disorder and fearful temperament

Fearful temperaments have been identified as a major risk factor for anxiety disorders. However, descriptions of fearful temperament and several forms of anxiety disorder show strong similarities. This raises the question whether these terms may simply refer to different aspects of the same underlying construct. The current review examines evidence for the overlap and distinction between these constructs. Although strong conclusions cannot be drawn from the extant literature, the bulk of the evidence appears to support a distinction between them.

Stable genetic influence on anxiety-related behaviours across middle childhood

We examined the aetiology of anxiety symptoms in an unselected population at ages 7 and 9, a period during which anxiety disorders first begin to develop (mean age at onset is 11 years). Specifically, the aim of the study was to investigate genetic and environmental continuity and change in components of anxiety in middle childhood. Parents of over 3,500 twin pairs completed the Anxiety-Related Behaviours Questionnaire (ARBQ) when twins were 7 and 9 years old. Multivariate-longitudinal analyses were conducted to examine genetic and environmental influences on stability and change in four anxiety scales: Negative Cognition, Negative Affect, Fear and Social Anxiety. We found moderate temporal stability in all four scales from 7 to 9 years (correlations ranging from 0.45 to 0.54) and moderate heritability (average 54%). Both shared and non-shared environmental influences were modest (average 18%-28% respectively). Genetic factors (68%) explained most of the homotypic continuity in anxiety. We show that homotypic continuity of Anxiety-Related Behaviours (i.e. the continuation of one specific type of anxiety over time) was largely driven by genetic factors. In contrast, though more varied, heterotypic continuity between some traits (i.e. the change from one type of anxiety-related behaviour into another over time) was mainly due to shared-environmental factors.

Interpersonal stress regulation and the development of anxiety disorders: an attachment-based developmental framework

Anxiety disorders represent a common but often debilitating form of psychopathology in both children and adults. While there is a growing understanding of the etiology and maintenance of these disorders across various research domains, only recently have integrative accounts been proposed. While classical attachment history has been a traditional core construct in psychological models of anxiety, contemporary attachment theory has the potential to integrate neurobiological and behavioral findings within a multidisciplinary developmental framework. The current paper proposes a modern attachment theory-based developmental model grounded in relevant literature from multiple disciplines including social neuroscience, genetics, neuroendocrinology, and the study of family factors involved in the development of anxiety disorders. Recent accounts of stress regulation have highlighted the interplay between stress, anxiety, and activation of the attachment system. This interplay directly affects the development of social-cognitive and mentalizing capacities that are acquired in the interpersonal context of early attachment relationships. Early attachment experiences are conceptualized as the key organizer of a complex interplay between genetic, environmental, and epigenetic contributions to the development of anxiety disorders - a multifactorial etiology resulting from dysfunctional co-regulation of fear and stress states. These risk-conferring processes are characterized by hyperactivation strategies in the face of anxiety. The cumulative allostatic load and subsequent "wear and tear" effects associated with hyperactivation strategies converge on the neural pathways of anxiety and stress. Attachment experiences further influence the development of anxiety as potential moderators of risk factors, differentially impacting on genetic vulnerability and relevant neurobiological pathways. Implications for further research and potential treatments are outlined.

Risk indicators of anxiety throughout adolescence: the TRAILS study

BACKGROUND

The aim was to identify risk indicators from preadolescence (age period 10-12) that significantly predict unfavorable deviations from normal anxiety development throughout adolescence (age period 10-17 years).

METHODS

Anxiety symptoms were assessed in a community sample of 2,220 boys and girls at three time-points across a 5-year interval. Risk indicators were measured at baseline and include indicators from the child, family, and peer domain. Associations with anxiety were measured with multilevel growth curve analyses.

RESULTS

A stable difference in anxiety over adolescence was found between high and low levels of a range of child factors (frustration, effortful control), family factors (emotional warmth received from parents, lifetime parental internalizing problems), and peer factor (victims of bullying) (P <.001). In contrast, the difference in anxiety between high and low levels of factors, such as self-competence, unfavorable parenting styles, and bully victims, decreased over adolescence (P <.001). For other family factors, associations were weaker (.05 <P <.001). Associations with parental education and family composition were not significant. Adjustment for concurrent depressive symptoms attenuated the associations, but those that were significant at P <.001 remained to be so. Specificity for anxiety subtypes (generalized anxiety, separation anxiety, social phobia, panic, and obsessive-compulsive symptoms) was reported for each association.

CONCLUSIONS

Several child, family, and peer factors measured in preadolescence were risk indicators of high levels of anxiety symptoms throughout adolescence. Some factors (such as rejective parenting) were vulnerability indicators for anxiety in early adolescence only, whereas other factors (such as peer victimization) were indicators of long-term elevated anxiety levels.

The modeling of internalizing disorders on the basis of patterns of lifetime comorbidity: associations with psychosocial functioning and psychiatric disorders among first-degree relatives

Two broadband latent factors--internalizing and externalizing--have frequently been identified in studies of the hierarchical structure of psychopathology. In the present research, 3 competing measurement models of putative internalizing disorders (i.e., a parsimonious single-factor model, a model based on the Diagnostic and Statistical Manual of Mental Disorders [4th ed., American Psychiatric Association, 1994], and an alternative model proposed by Krueger, 1999, and Watson, 2005) were evaluated in terms of their ability to account for lifetime patterns of diagnostic comorbidity. Four diagnostic assessments were performed on an age-based cohort of 816 persons over a 15-year interval. Each of the 3 measurement models demonstrated adequate or good fit to the data and similar approximating abilities. Additional analyses, however, suggested that nonspecific aspects of lifetime mood/anxiety or distress/fear disorders (i.e., general negative affect) largely accounted for indicators of psychosocial functioning at age 30 as well as densities of specific psychiatric disorders among the 1st-degree relatives of probands. The relevance of these findings for theoretical and descriptive models of internalizing disorders is discussed.

Parental anxiety and child symptomatology: an examination of additive and interactive effects of parent psychopathology. [corrected]

The current study examined relations between parent anxiety and child anxiety, depression, and externalizing symptoms. In addition, the study tested the additive and interactive effects of parent anxiety with parent depression and externalizing symptoms in relation to child symptoms. Forty-eight parents with anxiety disorders and 49 parents without any psychiatric disorder participated with one of their children (ages 6 to 14 years; 46.4% male; 75.8% Caucasian). Parent anxiety was related to both child anxiety and depression, but not child externalizing symptoms. Hierarchical regression analyses showed that only parent externalizing symptoms had additive effects, beyond parent anxiety symptoms, in relation to child anxiety symptoms. Further, parent anxiety symptoms moderated the relationship between parent and child externalizing symptoms, such that the strength of this relationship was reduced in the presence of high levels of parent anxiety symptoms. Results of this study illuminate the role of parent comorbidity in understanding relations between parent and child symptoms.

Early temperamental and family predictors of shyness and anxiety

With a sample of 242 twins (135 girls, 107 boys) studied longitudinally, behavioral inhibition (BI) and inhibitory control (IC) measured at 3 years, as well as early and concurrent family process variables, were examined as predictors of shyness and of anxiety symptoms approximately 4 years later. Structured observational data from laboratory and home contexts were used in conjunction with parent and experimenter ratings. A key goal was to extend previous findings of the positive relationship between early BI and anxiety development by incorporating the consideration of IC and family process variables. Using hierarchical linear modeling with restricted maximum likelihood estimation to adjust for twin dependency, early BI (b = 0.37, p < .01), IC (b = 0.14, p < .05), and concurrent lower family stress (b = -0.22, p < .05) predicted shyness during middle childhood. Findings were similar for parent-rated and laboratory-based shyness measures. Anxiety symptoms were predicted by BI (b = 0.14, p < .05), early negative family affect (b = 0.20, p < .05), and family stress in middle childhood (b = 0.26, p < .05). These findings clarify the relative importance of temperament and family factors in the development of both shyness and anxiety symptoms during childhood.

Childhood and adolescent anxiety and depression: beyond heritability

OBJECTIVE

To review the methodology of behavior genetics studies addressing research questions that go beyond simple heritability estimation and illustrate these using representative research on childhood and adolescent anxiety and depression.

METHOD

The classic twin design and its extensions may be used to examine age and gender differences in the genetic determinants of complex traits and disorders, the role of genetic factors in explaining comorbidity, the interaction of genes and the environment, and the effect of social interaction among family members. An overview of the methods typically employed to address such questions is illustrated by a review of 34 recent studies on childhood anxiety and depression.

RESULTS

The review provides relatively consistent evidence for small to negligible sex differences in the genetic etiology of childhood anxiety and depression, a substantial role of genetic factors in accounting for the temporal stability of these disorders, a partly genetic basis of the comorbidity between anxiety and depression, a possible role of the interaction between genotype and the environment in affecting liability to these disorders, a role of genotype-environment correlation, and a minor, if any, etiological role of sibling interaction.

CONCLUSION

The results clearly demonstrate a role for genetic factors in the etiology and temporal stability of individual differences in childhood anxiety and depression. Clinical implications of the findings are discussed.

Does childhood anxiety evoke maternal control? A genetically informed study

BACKGROUND

Despite theoretical and empirical support for an association between maternal control and child anxiety, few studies have examined the origins of this association. Furthermore, none use observer-ratings of maternal control within a genetically informative design. This study addressed three questions: 1) do children who experience maternal control report higher anxiety levels than those who do not?; 2) to what extent do genetic and environmental factors influence maternal control and child anxiety?; 3) to what extent do genetic and environmental factors influence the associations between child anxiety and maternal control?

METHOD

Five hundred and thirty 8-year-old children (from 265 twin pairs) and their mothers were observed participating in an 'etch-a-sketch' task from which maternal control was rated. Children rated their anxiety using the Screen for Child Anxiety Related Emotional Disorders.

RESULTS

Children who experienced maternal behaviour rated as 'extreme control' reported higher anxiety levels than those who did not. Maternal control was highly heritable (A = .63), high self-rated anxiety less so (h(2)(g) = .36). The overlap between high child anxiety and maternal control was primarily due to shared genetic factors.

CONCLUSIONS

These results suggest that maternal control is likely to have been elicited by children with high levels of anxiety.

The role of genes and environment in shaping co-occurrence of DSM-IV defined anxiety dimensions among Italian twins aged 8-17

This study investigated the ultimate causes of co-variation between symptoms of four common DSM-IV anxiety dimensions - Generalized Anxiety, Panic, Social Phobia and Separation Anxiety disorder - assessed with the Italian version of the Screen for Child Anxiety-Related Emotional Disorders questionnaire in a sample of 378 twin pairs aged 8-17 from the population-based Italian Twin Register. Genetic and environmental proportions of covariance between the targeted anxiety dimensions were estimated by multivariate twin analyses. Genetic influences (explaining from 58% to 99% of covariance) and unique environmental factors were the sole sources of co-variation for all phenotypes under study. Genetic influences associated with different anxiety dimensions coincide remarkably, as indicated by genetic correlations ranging from 0.40 to 0.61, while unique environmental overlap is less substantial. Thus, while additive genetic effects are important in explaining why children report symptoms from multiple anxiety disorders, environmental idiosyncratic factors seem to play a marginal role in shaping the co-occurrence of different anxiety dimensions in childhood.

Panic disorder: a review of DSM-IV panic disorder and proposals for DSM-V

This review covers the literature since the publication of DSM-IV on the diagnostic criteria for panic attacks (PAs) and panic disorder (PD). Specific recommendations are made based on the evidence available. In particular, slight changes are proposed for the wording of the diagnostic criteria for PAs to ease the differentiation between panic and surrounding anxiety; simplification and clarification of the operationalization of types of PAs (expected vs. unexpected) is proposed; and consideration is given to the value of PAs as a specifier for all DSM diagnoses and to the cultural validity of certain symptom profiles. In addition, slight changes are proposed for the wording of the diagnostic criteria to increase clarity and parsimony of the criteria. Finally, based on the available evidence, no changes are proposed with regard to the developmental expression of PAs or PD. This review presents a number of options and preliminary recommendations to be considered for DSM-V.

Co-occurring anxiety and disruptive behavior disorders: the roles of anxious symptoms, reactive aggression, and shared risk processes

The current review uses a developmental perspective to examine processes that may underlie and partially account for the association between anxiety disorders and disruptive behavior disorders among children and adolescents. We propose that one way to understand development of comorbid anxiety and disruptive behavior disorders is to examine symptoms that are precursors for or part of these syndromes, such as anxious symptoms and reactive aggression. We use a framework that considers these issues first at the syndrome or disorder level (e.g., anxiety disorders, disruptive behavior disorders), then at the symptom level (e.g., anxious symptoms and reactive aggression), and finally at the risk factor level (e.g., factors associated with anxious symptoms and/or reactive aggression). We apply various frameworks that have been put forth for understanding comorbidity of psychological syndromes to the co-occurrence of anxiety and disruptive behavior disorders and to the co-occurrence of reactive aggression and anxious symptoms where possible. We then identify gaps in the literature with regard to anxiety and reactive aggression, as well as anxiety and disruptive behavior disorders more generally. Finally, we provide a conceptual model describing how the relation of anxiety and reactive aggression may develop into clinically identifiable, comorbid anxiety and disruptive behavior disorders.

The development of anxiety disorders in childhood: an integrative review

We present an integrative review of the development of child anxiety, drawing on a number of strands of research. Family aggregation and genetic studies indicate raised vulnerability to anxiety in offspring of adults with the disorder (e.g. the temperamental style of behavioural inhibition, or information processing biases). Environmental factors are also important; these include adverse life events and exposure to negative information or modelling. Parents are likely to be key, although not unique, sources of such influences, particularly if they are anxious themselves. Some parenting behaviours associated with child anxiety, such as overprotection, may be elicited by child characteristics, especially in the context of parental anxiety, and these may serve to maintain child disorder. Emerging evidence emphasizes the importance of taking the nature of child and parental anxiety into account, of constructing assessments and interventions that are both disorder specific, and of considering bidirectional influences.

Investigating the association between autistic-like and internalizing traits in a community-based twin sample

OBJECTIVES

Recent research has suggested that children with autistic spectrum disorders often experience comorbid symptoms of anxiety and depression. However, despite this overlap, no quantitative genetic studies have addressed the phenotypic overlap and the etiologic association between internalizing and autistic-like traits within the general population. This study aimed to investigate the phenotypic and etiologic relation between internalizing and autistic-like traits using a community-based twin sample.

METHOD

We investigated the co-occurrence of these traits in a population-based sample of 3,233 twin pairs aged 8 to 9 years, using both parent- and teacher-report questionnaires. Bivariate structural equation modeling techniques were used to determine the extent to which internalizing and autistic-like traits shared common genetic and environmental influences.

RESULTS

Our results showed that there was a modest phenotypic correlation (r = 0.26-0.29) between autistic-like and internalizing traits. The traits were both substantially heritable but were largely independent with regard to their genetic influences (r(G) = 0.12-0.19). Shared environmental influences were modest but were largely common to both traits. Similar results were found using both parent- and teacher-reported data.

CONCLUSIONS

Internalizing and autistic-like traits showed moderate phenotypic overlap within the general population. This association was explained in small part by shared genetic factors, but the results suggested that most genetic influences were specific to either internalizing traits or autistic traits. Given these findings, we discuss the potential mechanisms that may underlie the relation between these traits.

Phenotypic and genetic differentiation of anxiety-related behaviors in middle childhood

BACKGROUND

Anxiety-related behaviors (ARBs) are commonly observed during typical development, yet few studies have investigated their etiology in middle childhood. This study aimed to examine both the phenotypic and genetic differentiation of ARB subtypes within the general population at age 7 and 9. It constituted a follow-up to an earlier study of ARBs in preschool children.

METHODS

We investigated the phenotypic structure of ARBs in a large population-based twin sample, comprising 7,834 twin pairs at age 7 and 3,644 twin pairs at age 9. Quantitative genetic modeling techniques were then used to determine the relative influences of genetic and environmental factors upon different types of ARB and upon the covariation between them.

RESULTS

Factor analysis supported the presence of five ARB factors at both ages: negative cognitions, negative affect, fear, obsessive-compulsive behaviors, and social anxiety. Multivariate genetic analyses revealed significant genetic effects and a small but significant influence of shared environment for all ARB subtypes. There was a moderate level of genetic specificity for each subtype as well as some shared genetic effects. Shared environmental influences correlated highly across all types of ARB, whereas nonshared environmental effects were largely subtype specific.

CONCLUSIONS

The current results suggest that ARBs can be differentiated both phenotypically and genetically within middle childhood, with subtypes reflecting symptom groupings of diagnosable disorders but also aspects of temperament. Although some etiological risk factors lead to a generalized vulnerability to anxiety, others may serve to differentiate between different types of ARBs.

Maternal and genetic effects on the acoustic startle reflex and its sensitization in C3H/HeN, DBA/2JHd and NMRI mice following blastocyst transfer

In the present study, reciprocal embryo transfers were conducted to examine genetic and maternal effects on the baseline and fear-sensitized acoustic startle response (ASR) in the two inbred strains C3H/HeN and DBA/2JHd and the outbred strain NMRI. The largest differences in the ASR were found in untreated strains (effect size 0.6). The transfer procedure per se had a significant effect on the behavior of NMRI mice resulting in a reduction in the baseline, and an increase in the fear-sensitized ASR. In contrast, there were no significant effects of the transfer procedure in the two inbred strains. Autosomal genetic effects had a stronger impact on the amplitude of the ASR (effect sizes 0.5) than sex (effect sizes 0.06) as revealed by reciprocal embryo transfer. Nevertheless, the genetic effects on the fear-sensitized ASR were somewhat more variable and strain-dependent (effect sizes 0.1-0.2). Global maternal effects were detected after embryo transfer into NMRI mothers resulting in a larger reduction of the ASR in the offspring of DBA and NMRI donors than C3H donors (effect sizes 0.1-0.2). An additional fostering procedure was introduced to dissect uterine and postnatal maternal effects in NMRI offspring. Uterine factors changed the baseline ASR of the offspring in direction of the recipient mother strain. Surprisingly, postnatal maternal effects on the ASR were contrary to the behavior of the rearing mother. In conclusion, both genetic and prenatal/postnatal maternal factors persistently influenced the ASR of the offspring, whereas the fear-sensitized ASR was mainly influenced by genetic factors. Our study shows that uterine and postnatal maternal influences deserve more attention when determining the phenotype of genetically engineered mice at least in the first generation following embryo transfer.

A multivariate genetic analysis of specific phobia, separation anxiety and social phobia in early childhood

BACKGROUND

Comorbidity amongst anxiety disorders is very common in children as in adults and leads to considerable distress and impairment, yet is poorly understood. Multivariate genetic analyses can shed light on the origins of this comorbidity by revealing whether genetic or environmental risks for one disorder also influence another. We examined the genetic and environmental influences on the comorbidity between three common childhood anxiety disorders: Specific Phobia, Separation Anxiety and Social Phobia.

METHODS

Using a two-phase design 4,662 twin-pairs were screened in the first phase and 854 pairs were assessed in the second phase by maternal-informant diagnostic interview using DSM-IV criteria.

RESULTS

Multivariate genetic analysis revealed significant shared environmental over-lap between Specific Phobia and Separation Anxiety and significant familial and non-shared environmental over-lap between Specific Phobia and Social Phobia.

CONCLUSIONS

Familial influences, especially shared environment, are central to the comorbidity between Specific Phobia and both Separation Anxiety and Social Phobia.

Finding gene-environment interactions for generalised anxiety disorder

It is becoming increasingly apparent that genetic research into psychiatric disorders would benefit from consideration of the environment because these risk mechanisms are likely to interact. Despite generalised anxiety disorder (GAD) being one of the most prevalent disorders presented in primary care, there is a paucity of published studies of gene-environment interactions (G x E) for this phenotype. This article describes how our current knowledge of GAD is useful in designing studies of G x E for GAD. To increase the chances of identifying replicable G x E for GAD further information is needed with regards to: defining and measuring GAD, difficulties co-occurring with GAD, quantitative genetic estimations for GAD, specific genes associated with GAD, and specific environmental risks for GAD.

In the face of uncertainty: a twin study of ambiguous information, anxiety and depression in children

Anxiety and depression share genetic influences, and have been associated with similar cognitive biases. Psychological theories of anxiety and depression highlight threat interpretations of ambiguity. Little is known about whether genes influence cognitive style, or its links to symptoms. We assessed ambiguous word and scenario interpretations, anxiety and depression symptoms in 300 8-year-old twin pairs. There were significant correlations between both negative interpretations of ambiguous words and scenarios and depression symptoms after controlling for anxiety symptoms (r = .13 and .31, respectively), but no significant correlations with anxiety independent of depression. Genetic effects ranged from 16% for depression to 30% for ambiguous word interpretations. Non-shared environmental influences were large (68-70%). Both genetic and environmental influences contributed to the association between depression and ambiguous scenario interpretations. These findings support psychological theories, which emphasise the role of environmental stress both on the development of threat interpretations and on their links with symptoms. The data also support a role for genetic influence on threat interpretations, which may mediate responses to stress.