Low extraversion and high neuroticism as indices of genetic and environmental risk for social phobia, agoraphobia, and animal phobia

OBJECTIVE: The authors examined the extent to which two major personality dimensions (extraversion and neuroticism) index the genetic and environmental risk for three phobias (social phobia, agoraphobia, and animal phobia) in twins ascertained from a large, population-based registry. METHOD: Lifetime phobias and personality traits were assessed through diagnostic interview and self-report questionnaire, respectively, in 7,800 twins from female-female, male-male, and opposite-sex pairs. Sex-limited trivariate Cholesky structural equation models were used to decompose the correlations among extraversion, neuroticism, and each phobia. RESULTS: In the best-fitting models, genetic correlations were moderate and negative between extraversion and both social phobia and agoraphobia, and that between extraversion and animal phobia was effectively zero. Genetic correlations were high and positive between neuroticism and both social phobia and agoraphobia, and that between neuroticism and animal phobia was moderate. All of the genetic risk factors for social phobia and agoraphobia were shared with those that influence extraversion and neuroticism; in contrast, only a small proportion of the genetic risk factors for animal phobia (16%) was shared with those that influence personality. Shared environmental experiences were not a source of correlations between personality traits and phobias, and unique environmental correlations were relatively modest. CONCLUSION: Genetic factors that influence individual variation in extraversion and neuroticism appear to account entirely for the genetic liability to social phobia and agoraphobia, but not animal phobia. These findings underline the importance of both introversion (low extraversion) and neuroticism in some psychiatric disorders.     

Comorbidity of panic disorder with agoraphobia and specific phobia: Relationship with the subtypes of specific phobia

The study objectives were to determine comorbidity rates for various subtypes of specific phobia (SP) in a sample of patients with the principal diagnosis of panic disorder with agoraphobia (PDA) and to examine the possible etiologic relatedness of these SP subtypes to PDA. Ninety consecutive day clinic patients with PDA were administered the Structured Clinical Interview for DSM-III-R (SCID) modified for DSM-IV. The overall comorbidity rate for SP was 65.6%. The most frequent subtypes of SP were situational phobia and dental phobia, followed by natural environment phobia, phobia of funerals, cemeteries, dead bodies, and other death-related phenomena and objects (referred to as death-related phobia), and blood-injection-injury phobia. Except for death-related phobia, other subtypes of SP clearly tended to precede the onset of PDA, often by many years. The Smallest difference between the age of onset for PDA and particular subtypes of SP (temporal distance) was found for death-related phobia, whereas the temporal difference was longer for situational phobia, hospital phobia, and blood-injection-injury phobia. The frequency and temporal distance data suggest that death-related phobia may constitute a risk factor for developing PDA or that it is a prodrome of PDA, whereas situational phobia, hospital phobia, and blood-injection-injury phobia appear to predispose to PDA to a lesser degree. Of the three broadly conceived groups of SP, mutilation phobias (which include death-related phobia, hospital phobia, blood-injection-injury phobia, and dental phobia) appear most etiologically relevant for PDA, with the group of situational phobias (which also includes the natural environment subtype of SP) being less relevant, and animal phobias showing a negligible etiologic relatedness to PDA.     

Mode of onset of simple phobia subtypes: further evidence of heterogeneity

Previous research has demonstrated heterogeneity of the simple phobia diagnostic category. As a further test of the notion of heterogeneity of the DSM-III-R simple phobia diagnostic category, mode of onset was examined in a sample of simple phobic outpatients. Patients were separated into one of four subtypes: animal or insect, blood and injury, situational, and choking-vomit phobias. Careful study yielded five distinct mode-of-onset categories. Two researchers independently determined the mode of onset for the patients studied: direct trauma, spontaneous, vicarious learning, gradual, and lifelong. Significant mode of onset differences were observed across groups. Situational phobics reported a preponderance of spontaneous onsets as compared to the other groups studied. These results offer further evidence of the heterogeneity of the simple phobia diagnostic category and also support the contention that situational simple phobias are closely related to agoraphobia.     

Effects of negative life experiences on phobia onset

Background: Conditioning theories, stress theories and social psychological theories each suggest that negative life experiences should influence phobia onset, though the patterns of effects suggested by each type of theory are different. Few previous studies have estimated the effects of a broad enough range of life experiences on onset of multiple types of phobia to evaluate patterns of effects. Methods: Retrospective data on life experiences and history of phobia from a representative sample of persons 15–54 years old from the US population (the National Comorbidity Survey) are analyzed using discrete-time event history methods. Results: The effects of 12 negative life events and ten chronic childhood adversities on onset of agoraphobia, specific phobia, and social phobia are presented. Three discrete events have unique effects on agoraphobia onset: life threatening accidents, combat in war (for men), and a fire/flood or other natural disaster. Two chronic experiences during childhood have unique effects on specific phobia onset: violence at the hands of one or more adults, and verbal aggression between parents. Sexual assault by a relative and verbal aggression between parents have unique effects on social phobia onset. The effect of sexual assault by a relative on social phobia is confined to women, and to phobias beginning before age 12. Conclusions: Unpredictable and uncontrollable events that threaten or result in physical harm influence agoraphobia onset. Potentially predictable but difficult to control childhood experiences (e.g., chronic parental violence) influence specific phobia onset. Blame is a likely mediator of the effect of sexual abuse on social phobia. No data on perceptions of predictability and controllability of life experiences, or of blame, were available for analysis. These conclusions are therefore based on speculations about social psychological processes that have been supported by previous research and theory. Accepted: 18 December 1998     

Epidemiology of specific phobia subtypes: findings from the Dresden Mental Health Study.

This study determined the prevalence, age of onset, comorbidity, and impairment associated with specific phobia subtypes in the community. Data were drawn from the Dresden Mental Health Study (N=2064), a representative community-based sample of young women in Dresden, Germany. The lifetime prevalence of any specific phobia was 12.8%, with subtypes ranging in prevalence between 0.2% (vomiting, infections) and 5.0% (animals). There were significant differences in the mean age of onset of specific phobias. Significant differences in comorbidity patterns also emerged between subtypes. No significant differences were found in level of impairment associated with the subtypes. The findings suggest that specific phobias are common among young women and that they differ in prevalence, associated comorbidity, and mean age of onset. These data suggest significant differences in the phenomenology and clinical significance of specific phobia subtypes.     

The relationship between agoraphobia, social phobia and blood-injury phobia in phobic and anxious-depressed patients

This paper reports the results of principal components and stepwise discriminant analyses of anxiety, depression and fear scores for 74 phobic and anxious-depressed psychiatric patients. Factor analysis indicated a coherent agoraphobia factor, with less coherent blood-injury and social phobia factors. Discriminant analysis showed a high degree of correct classification of diagnosed agoraphobic, blood-injury and social phobic patients particularly for agoraphobia. A frequency distribution of the phobia scores indicated an all or nothing quality to agoraphobic fears. The results indicate that agoraphobia is a fairly coherent syndrome, but that more work is needed on the concepts and measurement of blood-injury and social phobias.     

The structure of genetic and environmental risk factors for anxiety disorders in men and women

BACKGROUND: The anxiety disorders exhibit high levels of lifetime comorbidity with one another. Understanding the underlying causes of this comorbidity can provide insight into the etiology of the disorders and inform classification and treatment. OBJECTIVE: To explain anxiety disorder comorbidity by examining the structure of the underlying genetic and environmental risk factors. DESIGN: Lifetime diagnoses for 6 anxiety disorders (generalized anxiety disorder, panic disorder, agoraphobia, social phobia, animal phobia, and situational phobia) were obtained during personal interviews from a population-based twin registry. Multivariate structural equation modeling that allowed for sex differences was performed. SETTING: General community sample. PARTICIPANTS: More than 5000 members of male-male and female-female twin pairs from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders. MAIN OUTCOME MEASURES: Parameter estimates for best-fitting model. RESULTS: The full model, which contained 2 common genetic, shared environmental, and unique environmental factors plus disorder-specific factors, could be constrained to equality across male and female study participants. In the best-fitting model, the genetic influences on anxiety were best explained by 2 additive genetic factors common across the disorders. The first loaded most strongly in generalized anxiety disorder, panic disorder, and agoraphobia, whereas the second loaded primarily in the 2 specific phobias. Social phobia was intermediate in that it was influenced by both genetic factors. A small role for shared environmental influences was observed owing to a single common factor that accounted for less than 12% of the total variance for any disorder. Unique environmental influences could be explained by a single common factor plus disorder-specific effects. CONCLUSIONS: The underlying structure of the genetic and environmental risk factors for the anxiety disorders is similar between men and women. Genes predispose to 2 broad groups of disorders dichotomized as panic-generalized-agoraphobic anxiety vs the specific phobias. The remaining associations between the disorders are largely explained by a unique environmental factor shared across the disorders and, to a lesser extent, a common shared environmental factor.     

The genetic epidemiology of irrational fears and phobias in men

BACKGROUND: Much of our knowledge of the role of genetic factors in the etiology of phobias comes from one population-based sample of female twins. We examined the sources of individual differences in the risks for phobias and their associated irrational fears in male twins. METHODS: In personal interviews with both members of 1198 male-male twin pairs (707 monozygotic [MZ] and 491 dizygotic [DZ]) ascertained from a population-based registry, we assessed the lifetime history of agoraphobia and social, animal, situational, and blood/injury phobias as well as their associated irrational fears. Twin resemblance was assessed by means of probandwise concordance, odds ratios, tetrachoric correlations, and univariate and multivariate biometrical model fitting. RESULTS: The suggestive results obtained by analysis of phobias only were supported by analyzing both fears and phobias. All 5 phobia subtypes aggregate within twin-pairs. This aggregation is due largely or solely to genetic factors with heritability of liabilities ranging from 25% to 37%. Multivariate analysis revealed a common genetic factor, genetic factors specific to each subtype, and a common familial-environmental factor. CONCLUSIONS: In male subjects, genetic risk factors, which are partially common across all subtypes and partially subtype specific, play a moderate role in the etiology of phobias and their associated irrational fears. Family environment probably has an impact on risk for agoraphobia and social phobia. The genetic liability to blood/injury phobias is not distinct from those of the more typical phobias.     

Clinical features of four DSM-IV-specific phobia subtypes

Seventy-three patients (ages 18 to 66) with specific phobias from one of four DSM-IV subtypes (animal, situational, blood-injection-injury, and natural environment) were assessed by experienced clinicians using a semistructured diagnostic interview. All patients were free of lifetime anxiety comorbidity. Subtype groups were compared on age of onset, mode of onset, presence of unexpected panic attacks, and focus of fear. Consistent with earlier findings, participants with situational phobia had a later age of onset and more unexpected panic attacks. No differences were found across subtypes in mode of onset. Contrary to previous findings, natural environment and situational phobias were most frequently associated with a focus on danger or harm rather than other foci such as internal sensations associated with panic attacks. Implications for the usefulness of current subtype categories are discussed.     

The Zurich study

Summary The problems in association with agoraphobia and social phobia were examined in an 11-year prospective longitudinal study of a Swiss cohort of young adults. The weighted prevalence rates according to DSM-III were 2.9% for agoraphobia and 3.8% for social phobia. Although the problem of agoraphobia was greater in females, an equal sex ratio was observed for social phobia. There was a significant degree of comorbility between the two subtypes of phobia, with females exhibiting a significantly greater frequency of co-occurrence of both disorders than males. The course of the two disorders was quite similar. In general, subjects with both disorders reported a more severe course. Assessment of comorbidity of phobias and other disorders revealed that agoraphobia was most significantly associated with extended neurasthenia, sexual problems, and the consumption of cannabis. On the other hand, social phobia was associated with other disorders than agoraphobia, with the strongest associations emerging for simple phobia, extended insomnia, and alcohol abuse. These findings support the validity of the distinction between different subtypes of phobia. The longitudinal analysis revealed that also phobia in general was not stable at the diagnostic level phobic symptoms were quite persistent across time.     

The etiology of phobias: an evaluation of the stress-diathesis model

BACKGROUND: We evaluated for phobias the prediction of the stress-diathesis model that the magnitude of stress at onset is inversely proportional to the level of underlying diathesis. METHODS: In more than 7500 twins from a population-based registry, we assessed the personality trait of neuroticism--as an index of phobia-proneness--and the lifetime histories of 5 phobia subtypes (agoraphobia, social, animal, situational, and blood or injury) and their associated irrational fears. Interviewers classified the mode of acquisition of the fear in phobic twins into 5 possible categories: trauma to self (further divided by severity), observed trauma to others, observed fear in others, taught by others to be afraid, and no memory of how or why fear developed. Analyses were conducted by logistic regression and analysis of covariance. RESULTS: The mode of acquisition had moderate test-retest reliability and differed meaningfully across phobia subtypes. None of the 3 tests of the stress-diathesis model was confirmatory: (1) the risk of phobias was not elevated in co-twins of twins who had no memory of their mode of acquisition, (2) the risk of phobias was not decreased in co-twins of twins who had severe trauma to self, and (3) no significant relationship, in phobic twins, was found between levels of neuroticism and mode of acquisition. CONCLUSIONS: These results are inconsistent with the traditional etiologic theories for phobias, which assume conditioning or social transmission. However, they are compatible with nonassociative models, which postulate that the vulnerability to phobias is largely innate and does not arise directly from environmental experiences. The stress-diathesis model may not be an appropriate paradigm for phobic disorders.     

A review and meta-analysis of the heritability of specific phobia subtypes and corresponding fears

Evidence from twin studies suggests that genetic factors contribute to the risk of developing a fear or a phobia. The aim of the present study was to review the current literature regarding twin studies describing the genetic basis of specific phobias and their corresponding fears. The analysis included five twin studies on fears and ten twin studies on specific phobias. Heritability estimates of fear subtypes and specific phobia subtypes both varied widely, even within the subtypes. A meta-analysis performed on the twin study results indicated that fears and specific phobias are moderately heritable. The highest mean heritability (±SEM) among fear subtypes was found for animal fear (45% ± 0.004), and among specific phobias for the blood–injury–injection phobia (33% ± 0.06). For most phenotypes, variance could be explained solely by additive genetic and unique environmental effects. Given the dearth of independent data on the heritability of specific phobias and fears, additional research is needed.     

Simple phobia: evidence for heterogeneity

Although simple phobia is a residual category in DSM-III, clinical experience suggests at least four subtypes of this group. To test the validity of the subtypes, the authors compared patients with one of four simple phobias subtypes (n: animal-insect = 25, blood-injury = 9, situational = 46, choking-vomit = 8). Significant sex differences were observed; all animal and insect phobics and seven of eight choking-vomit phobics were female, while the other two groups showed approximately equal numbers of males and females. Mean age of onset was significantly older for situational phobics than animal-insect or blood-injury phobics; choking-vomit probands were intermediate. Frequency of situational phobias differed significantly among relatives of the four proband groups, with highest frequency being found among situational probands. Thus, these clinical and epidemiological variables support the separation of simple phobia into at least these four diagnostic groups.     

Considering comorbidity in social phobia

BACKGROUND: Considering comorbidity in social phobia contributes to our understanding of causal pathways and improved classifications for psychiatric disorders. Comorbidity also has important clinical implications. While a number of studies have investigated comorbidity in social phobia, only one other study has used the Composite International Diagnostic Interview (CIDI) and considered comorbidity in subtypes of social phobia. This study evaluated lifetime social phobia comorbidity with other common mental disorders as well as comorbidity in subtypes of social phobia. We also considered whether social fears, reported by respondents with social phobia, had an earlier or later age of onset than other disorders. METHODS: Data came from the Mental Health Supplement to the Ontario Health Survey, a survey of 8,116 Canadian respondents, ages 15-64. Psychiatric diagnoses were determined using the CIDI. This instrument is considered more sensitive than earlier instruments for diagnosing social phobia. RESULTS: Fifty-two percent of respondents with lifetime social phobia reported at least one other lifetime mental disorder and 27% reported three or more lifetime mental disorders. Social phobia, in this sample, is strongly comorbid with anxiety and affective disorders, and moderately comorbid with substance abuse disorders. When two social phobia subgroups were considered, the largest odds ratios were found among the not-exclusively-speaking social phobia group. This subgroup would include most of the respondents with a generalized form of social phobia. Age of onset of social fears, in respondents with social phobia, preceded age of onset of the comorbid disorder in 32% of cases with comorbid anxiety disorder, 71% of cases with comorbid affective disorder and 80% of cases with comorbid substance dependence/abuse disorder. CONCLUSIONS: Comorbidity and relative age of onset among respondents with social phobia in this study are generally consistent with previous epidemiologic studies. Clinicians should be vigilant for comorbidity in social phobia and should select treatments that target the full range of comorbid disorders. Early intervention or prevention of social fears or social phobia has the potential to reduce the risk of comorbid disorders.     

The association between social phobia, social anxiety cognitions and paranoid symptoms

Schutters SIJ, Dominguez M‐d‐G, Knappe S, Lieb R, van Os J, Schruers KRJ, Wittchen H‐U. The association between social phobia, social anxiety cognitions and paranoid symptoms. Objective: Previous research suggests high levels of comorbidity between social phobia and paranoid symptoms, although the nature of this association remains unclear. Method: Data were derived from the Early Developmental Stages of Psychopathology study, a 10‐year longitudinal study in a representative German community sample of 3021 participants aged 14–24 years at baseline. The Munich‐Composite International Diagnostic Interview was used to assess social phobia and paranoid symptoms, along with data on social phobia features. Cross‐sectional and longitudinal analyses were conducted. Differential associations with environmental risk factors and temperamental traits were investigated. Results: Lifetime social phobia and paranoid symptoms were associated with each other cross‐sectionally (OR = 1.80, 95% CI = 1.31–2.47). Lifetime paranoid symptoms were associated specifically with social anxiety cognitions. Lifetime cognitions of negative evaluation predicted later onset of paranoid symptoms, whereas onset of social phobia was predicted by cognitions of loss of control and fear/avoidance of social situations. Lifetime social phobia and paranoid symptoms shared temperamental traits of behavioural inhibition, but differed in environmental risks. Conclusions: The present study showed that paranoid symptoms and social phobia share similarities in cognitive profile and inhibited temperament. Avoidance appears to be important in the development of social phobia, whereas cannabis use and traumatic experiences may drive paranoid thinking in vulnerable individuals.     

Comorbidity and social phobia: evidence from clinical,epidemiologic, and genetic studies

This paper reviews evidence from clinical, epidemiologic, and family studies regarding the association between social phobia and other syndromes. Social phobia is strongly associated with other anxiety disorders, substance abuse, and affective disorders in both clinical and community samples. An average of 80% of social phobics identified in community samples meet diagnostic criteria for another lifetime condition. Social phobia is most strongly associated with other subtypes of anxiety disorders, with an average of 50% of social phobics in the community reporting a concomitant anxiety disorder including another phobic disorder, generalized anciety, or panic disorder. Approximately 20% of subjects in the community meet lifetime criteria for a major depressive disorder. The onset of social phobia generally precedes that of all other disorders, with the exception of simple phobia. Both clinical severity and treated prevalence are consistently greater among social phobics with comorbid disorders The results of family and twin studies reveal that shared etiologic factors explain a substantial proportion of the comorbidity between social phobia and depression, whereas the association between social phobia and alcoholism derives from a nonfamilial causal relationship between the two conditions. Clinical and phenomenologic implications of these findings are discussed.     

Prevalence,correlates, and comorbidities of four DSM-IV specific phobia subtypes: Results from the Korean Epidemiological Catchment Area study

Although several studies have detected differences in clinical features among specific phobias, there is a shortage of detailed national data on the on the DSM-IV SP subtypes, particularly in the Asian population. To examine the prevalence, demographic and other correlates, and co-morbidities of DSM-IV SP subtypes in a nationwide sample of Korean adults. We recruited 6510 participants aged 18–64 years for this study. Lay interviewers used the Composite International Diagnostic Interview to assess participants. We analyzed socio-demographics, health-related correlates and frequencies of comorbid mental disorders among participants with SP and each subtypes compared to unaffected adults. The prevalence of lifetime DSM-IV SP was 3.8%, and animal phobias were the most prevalent type of SP. Blood–injection–injury phobia was negatively associated with education, whereas situational phobia was positively associated with education. The strongest mental disorder comorbidity was associated with situational phobia; there is a higher probability of comorbid mood (OR=5.73, 95% CI=2.09–15.73), anxiety (OR=7.54, 95% CI=2.34–24.28), and somatoform disorders (OR=7.61, 95% CI=1.64–35.22) with this subtype. Blood–injection–injury phobia was highly associated with alcohol dependence (OR=9.02, 95% CI=3.54–23.02). Specific phobias are heterogeneous with respect to socio-demographic characteristics and comorbidity pattern. Implications of the usefulness of current subtype categories should continue to be investigated.     

The relationship between avoidant personality disorder and social phobia: a population-based twin study

OBJECTIVE: The purpose of this study was to determine the sources of comorbidity for social phobia and dimensional representations of avoidant personality disorder by estimating to what extent the two disorders are influenced by common genetic and shared or unique environmental factors versus the extent to which these factors are specific to each disorder. METHOD: Young adult female-female twin pairs (N=1,427) from the Norwegian Institute of Public Health Twin Panel were assessed at personal interview for avoidant personality disorder and social phobia using the Structured Interview for DSM-IV Personality and the Composite International Diagnostic Interview. Bivariate Cholesky models were fitted using the Mx statistical program. RESULTS: The best-fitting model included additive genetic and unique environmental factors only. Avoidant personality disorder and social phobia were influenced by the same genetic factors, whereas the environmental factors influencing the two disorders were uncorrelated. CONCLUSIONS: Within the limits of statistical power, these results suggest that there is a common genetic vulnerability to avoidant personality disorder and social phobia in women. An individual with high genetic liability will develop avoidant personality disorder versus social phobia entirely as a result of the environmental risk factors unique to each disorder. The results are in accordance with the hypothesis that psychobiological dimensions span the axis I and axis II disorders.     

Three cases of overlap between panic disorder, social phobia, and agoraphobia

Panic disorder, agoraphobia, and social phobia are subtypes of the anxiety disorders as defined by DSM-III. Panic disorder and agoraphobia are thought to be closely related, whereas social phobia is considered to be distinct on the basis of demographic characteristics, course, symptoms, biological responsiveness, and treatment specificity. Three cases are presented in which these classificatory distinctions are blurred and the course of the illness seems to involve temporally overlapping manifestations of panic attacks, social phobia, and agoraphobia. Diagnostic and treatment issues and implications for research are discussed.     

A population-based twin study of the relationship between neuroticism and internalizing disorders

OBJECTIVE: The anxiety and depressive disorders exhibit high levels of lifetime comorbidity with one another. The authors examined how genetic and environmental factors shared by the personality trait neuroticism and seven internalizing disorders may help explain this comorbidity. METHOD: Lifetime major depression, generalized anxiety disorder, panic disorder, agoraphobia, social phobia, animal phobia, situational phobia, and neuroticism were assessed in over 9,000 twins from male-male, female-female, and opposite-sex pairs through structured diagnostic interviews. Multivariate structural equation models were used to decompose the correlations between these phenotypes into genetic and environmental components, allowing for sex-specific factors. RESULTS: Genetic factors shared with neuroticism accounted for between one-third and one-half of the genetic risk across the internalizing disorders. When nonsignificant gender differences were removed from the models, the genetic correlations between neuroticism and each disorder were high, while individual-specific environmental correlations were substantially lower. In addition, the authors could identify a neuroticism-independent genetic factor that significantly increased risk for major depression, generalized anxiety disorder, and panic disorder. CONCLUSIONS: There is substantial, but not complete, overlap between the genetic factors that influence individual variation in neuroticism and those that increase liability across the internalizing disorders, helping to explain the high rates of comorbidity among the latter. This may have important implications for identifying the susceptibility genes for these conditions.