Temperamental correlates of disruptive behavior disorders in young children: preliminary findings

BACKGROUND

Our objective was to test the hypothesis that temperamental behavioral disinhibition measured in early childhood would be associated with disruptive behavior disorders.

METHODS

We used variables from laboratory-based behavioral observations originally devised to assess behavioral inhibition to construct a theory-based a priori definition of "behavioral disinhibition" in 200 young children at-risk for panic disorder, depression, or both and 84 children of parents without anxiety or major depressive disorder. We then compared behaviorally disinhibited and nonbehaviorally disinhibited children on rates of DSM-III-R disorders and measures of academic and social dysfunction.

RESULTS

Behavioral disinhibition was significantly associated with higher rates of disruptive behavior disorders and mood disorders. Children with behavioral disinhibition were significantly more likely than nondisinhibited, noninhibited children to have attention-deficit/hyperactivity disorder (ADHD) and to have comorbid mood and disruptive behavior disorders. Moreover, disinhibited children had lower Global Assessment of Functioning Scale scores and were more likely to have been in special classes and to have problems with school behavior and leisure activities.

CONCLUSIONS

These results suggest that behavioral disinhibition may represent a temperamental precursor to disruptive behavior problems, particularly ADHD. Longitudinal studies using behavioral assessments of behavioral disinhibition are needed to confirm these findings.

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.

Linkage genome scan for loci predisposing to panic disorder or agoraphobia

We conducted a 10 cM linkage genome scan in a set of 20 American pedigrees (153 subjects), ascertained through probands with panic disorder (PD). Several anxiety disorders segregate in these families; they were diagnosed on the basis of Schedule for Affective Disorders and Schizophrenia interview. In this article, we describe results for panic disorder and agoraphobia, which are closely related, common, heritable anxiety disorders. This is the first complete linkage genome scan for agoraphobia and the third for PD. A total of 407 markers (389 autosomal, 18 X chromosome) were genotyped. Multipoint LOD score and NPL analysis were completed using GENEHUNTER2. For PD, two genomic regions meet criteria for suggestive linkage. One of these regions is on chromosome 1 (LOD score = 2.04). This region coincides with a region that generated a LOD score of 1.1 in a previous genome scan by Crowe et al. [2001: Am J Med Genet (Neuropsychiatr Genet) 105:105-109]. The other (LOD score = 2.01) is located on chromosome 11p and occurs at marker CCKBR, one of eight candidate genes examined. For agoraphobia, the most promising potential linkage was on chromosome 3 (NPL score = 2.75; P = 0.005). This was accounted for primarily by a single family that by itself generated an NPL score of 10.01 (P = 0.0039) and a LOD score of 2.10. These results provide initial evidence for a genetic locus on chromosome 3 that contributes to risk for agoraphobia. They also support suggestive linkage to two risk loci for panic disorder. Additional potential loci were identified with lesser statistical support; several of these were consistent with previously reported panic disorder linkage results. Overall, the results presented here suggest that PD and agoraphobia are complex traits that share some, but not all, of their susceptibility loci. Published 2001 Wiley-Liss, Inc.

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.

Patterns of psychopathology and dysfunction in high-risk children of parents with panic disorder and major depression

OBJECTIVE

The purpose of the study was to evaluate 1) whether an underlying familial predisposition is shared by all anxiety disorders or whether specific risks are associated with specific disorders, and 2) whether panic disorder and major depression have a familial link.

METHOD

The study compared four groups of children: 1) offspring of parents with panic disorder and comorbid major depression (N=179), 2) offspring of parents with panic disorder without comorbid major depression (N=29), 3) offspring of parents with major depression without comorbid panic disorder (N=59), and 4) offspring of parents with neither panic disorder nor major depression (N=113).

RESULTS

Parental panic disorder, regardless of comorbidity with major depression, was associated with an increased risk for panic disorder and agoraphobia in offspring. Parental major depression, regardless of comorbidity with panic disorder, was associated with increased risks for social phobia, major depression, disruptive behavior disorders, and poorer social functioning in offspring. Both parental panic disorder and parental major depression, individually or comorbidly, were associated with increased risk for separation anxiety disorder and multiple (two or more) anxiety disorders in offspring.

CONCLUSIONS

These findings confirm and extend previous results documenting significant associations between the presence of panic disorder and major depression in parents and patterns of psychopathology and dysfunction in their offspring.

Exonic variants of the GABA(B) receptor gene and panic disorder

The enhancement of GABAergic neurotransmission has been closely linked to antipanic drug efficacy. This is the first study to investigate a putative association of exonic sequence variants of the human GABA(B) receptor 1 (GABA(B)R1) gene and susceptibility to panic disorder. Three DNA sequence variants in exons 1a1, 7 and 11 were assessed by polymerase chain reaction-based restriction fragment length polymorphism in a case-control study among patients with panic disorder with and without agoraphobia (DSM III-R criteria) and blood donors. There was no indication of an increased vulnerability to panic disorder or agoraphobia with respect to the allelic variants under study.

Panic and phobic anxiety: defining phenotypes for genetic studies

OBJECTIVE

With recent advances in molecular genetics, the rate-limiting step in identifying susceptibility genes for psychiatric disorders has become phenotype definition. The success of psychiatric genetics may require the development of a "genetic nosology" that can classify individuals in terms of the heritable aspects of psychopathology. The authors' aim is to begin to apply this analysis to the anxiety disorders, focusing on panic and phobic disorders.

METHOD

Two parallel traditions of defining anxiety phenotypes are reviewed: the first, more closely identified with clinical psychiatry, has identified categorical diagnoses (e.g., panic disorder and social phobia). The other, more closely identified with psychological studies of personality development, has examined dimensional traits (e.g., neuroticism) and anxious temperament (e.g., behavioral inhibition).

RESULTS

The authors suggest that a genetic nosology of panic and phobic disorders may incorporate features of both traditions and discuss strategies for optimizing genetic approaches to anxiety including 1) studying phenotypic extremes, 2) identifying biological trait markers, and 3) using animal models to identify candidate loci.

CONCLUSIONS

An important dividend from the effort to define the boundaries of heritable phenotypes for genetic studies of anxiety may be a refinement of the nosology of anxiety disorders.

Anticipation of age at onset in panic disorder

OBJECTIVE

Anticipation (i.e., the decrease in age at onset or the increase in severity of a disorder in successive generations) has recently been reappraised as a key to understanding the genetics of some familial illnesses. The purpose of this study was to search for possible anticipation in panic disorder.

METHOD

Thirty-eight unilineal, multigenerational families with multiple directly interviewed members who had panic disorder were compared across two successive generations for 1) age at the first panic attack, 2) age at the onset of panic disorder, and 3) the highest degree of agoraphobia ever experienced, as a tentative index of severity of illness. Intergenerational pairwise comparisons were implemented according to four different sampling schemes: random pairs, random transmitting pairs, all possible pairs, and all possible transmitting pairs.

RESULTS

Life table analyses showed a significant decrease in the time before the first episode of panic and onset of panic disorder from the older to the younger generation. Evidence for anticipation was found for both indexes of onset in all four sampling schemes. No evidence of a generational effect on the index of severity of agoraphobia was found. Corrections for possible biases suggested that these results are not likely to be simple artifacts.

CONCLUSIONS

Anticipation is supported in this specific set of families and, if it is confirmed by other studies, a role for trinucleotide repeat sequences may be considered to account for the familial aggregation of panic disorder.

Candidate gene study of eight GABAA receptor subunits in panic disorder

OBJECTIVE

gamma-Aminobutyric acid type A (GABAA) receptor subunit genes are candidate genes for panic disorder. Benzodiazepine agonists acting at this receptor can suppress panic attacks, and both inverse agonists and antagonists can precipitate them. The human GABAA receptor subtypes are composed of various combinations of 13 subunits, each encoded by a unique gene. The authors tested eight of these subunits in a candidate gene linkage study of panic disorder.

METHOD

In 21 U.S. and five Icelandic multiplex pedigrees of panic disorder, 104 individuals had DSM-III-R panic disorder (the narrowly defined affected phenotype) and 134 had either this diagnosis or subsyndromal panic disorder characterized by panic attacks that failed to meet either the criterion of attack frequency or the number of criterion symptoms necessary for a definite diagnosis (the broadly defined affected phenotype). The authors conducted lod score linkage analyses with both phenotypes using both a dominant and a recessive model of inheritance for the following loci: GABRA1-GABRA5 (alpha 1-alpha 5), GABRB1 (beta 1), GABRB3 (beta 3), and GABRG2 (gamma 2).

RESULTS

The results failed to support the hypothesis that any of these genes cause panic disorder in a majority of the pedigrees.

CONCLUSIONS

Within the limitations of the candidate gene linkage method, panic disorder does not appear to be caused by mutation in any of the eight GABAA receptor genes tested.

Platelet alpha 2-adrenoreceptors, catecholamines, hemodynamic variables, and anxiety in panic patients and their asymptomatic relatives

The objectives of this study were to a) replicate our prior finding of a decreased number (Bmax) of platelet alpha 2-adrenoreceptors in panic disorder, b) determine if binding is also decreased in asymptomatic first-degree relatives of panic patients (known to be at increased risk for developing panic), and c) evaluate the effect of treatment on the presumptive decrease in binding (i.e., is the decrease a state or a trait marker for panic?). Panic patients had clonidine and yohimbine platelet-binding assays, symptom ratings, and measurement of lying and standing plasma epinephrine, norepinephrine, systolic and diastolic blood pressure, and heart rate before treatment, after approximately 2 months of medication (fluoxetine, tricyclics, or alprazolam) and/or cognitive behavioral treatment, and after symptom remission while drug free; normal subjects had determinations of the same measures at approximately the same time intervals. Relatives of both groups had one determination only of all measures. Tritiated clonidine binding was decreased and lying heart rate was increased in patients before treatment. Magnitude of binding decrease was correlated with symptom severity and standing norepinephrine. No binding abnormality was seen in first-degree relatives of patients. Treatment increased clonidine binding in patients. Both patients and relatives of patients showed significantly increased standing plasma norepinephrine in comparison to controls. There is a state-related decrease in binding, associated with symptom severity and norepinephrine, in panic disorder. Abnormal reactivity of norepinephrine to standing might be a marker for increased likelihood of panic development in individuals at risk.

Panic disorder and social phobia: effects of comorbidity on familial transmission

The aim of this study was to examine effects of comorbidity of panic disorder and social phobia on familial transmission of each of these disorders. Rates of panic disorder and social phobia were compared in directly interviewed relatives of four proband groups: (1) panic disorder, (2) social phobia, (3) panic disorder and social phobia, and (4) never ill controls. Anxiety disorder probands had no additional lifetime anxiety disorder comorbidity. The familial pattern of the comorbid (panic disorder and social phobia) probands resembled that of the panic disorder group: an increased rate of panic disorder but not social phobia as compared to relatives of controls. Relatives of social phobia probands had an increased rate of social phobia but not panic disorder. These data indicate that social phobia in individuals who subsequently develop panic disorder: (1) differs with respect to familial transmission from social phobia which occurs without lifetime anxiety comorbidity; and (2) may be nonfamilial and/or causally related to panic disorder. Additional studies in larger epidemiologic samples are required to assess generalizability of these findings.

Somatotype in panic patients

The aim of the study was to test whether an association exists between asthenic somatotype, as measured by the Quetelet index, and panic and or agoraphobia. Ninety-nine cases with panic and/or agoraphobia diagnosed at the psychiatric outpatient clinic of a general teaching hospital were compared to 99 controls with psychiatric conditions other than panic and agoraphobia, and to 64 medical controls, matched by age and gender. No differences in weight, height and raw Quetelet and ponderal indexes were found between panic cases and controls. However, 33.3% of cases, but only 19.2% of psychiatric controls and 18.7% of medical controls, were in the asthenic group as defined by the lower quartile of the Quetelet index (age and sex adjusted odds ratio = 2.33, 95% C.I.: 1.21-4.11). In the entire sample, the asthenic somatotype was associated with lower age and with the presence of hypermobility of joints. Since both panic disorder and mitral valve prolapse may be associated with the joint hypermobility syndrome (JHS), an inherited disorder of collagen synthesis, it is suggested that the relationship found between panic and asthenic somatotype might be mediated through JHS.

Age at onset of panic disorder: influence of familial liability to the disease and of childhood separation anxiety disorder

OBJECTIVE

The authors investigated the relation of age at onset of panic disorder to liability to panic disorder and agoraphobia.

METHOD

Two hundred thirty-one outpatients with panic disorder were compared with 131 surgical outpatients on demographic variables and familial risk of psychiatric disorders. The distribution of patients' ages at onset of panic disorder and several covariates were entered in a stepwise survival analysis.

RESULTS

The patients with panic disorder had a significantly higher rate of childhood separation anxiety disorder and higher familial risks of panic disorder/panic disorder with agoraphobia and alcoholism. A family history of panic disorder with agoraphobia and the presence of childhood separation anxiety disorder influenced age at onset of panic disorder.

CONCLUSIONS

Age at onset of panic disorder may reflect genetic penetrance, and separation anxiety disorder may be an individual predictor of earlier onset of panic disorder.

Hypersensitivity to inhalation of carbon dioxide and panic attacks

Thirteen healthy subjects with infrequent panic attacks and without agoraphobia who did not meet DSM-III-R criteria for panic disorder, 43 patients with panic disorder, and 43 healthy control subjects who never experienced panic attacks underwent one vital capacity inhalation of 35% CO2. Healthy subjects with infrequent panic attacks reacted similarly to patients with panic disorder and more strongly than healthy subjects who never experienced panic attacks. The results suggest that (a) subjects with sporadic unexpected panic attacks and patients with panic disorder belong to the same spectrum of vulnerability and (b) CO2 hypersensitivity might be a trait marker of panic attacks rather than of a clinical diagnosis of panic disorder.

Genetic factors in early separation anxiety: implications for the genesis of adult anxiety disorders

An important contemporary conceptualization of anxiety has suggested that heightened early separation anxiety is specifically associated with the risk of adult panic disorder, with hereditary factors underlying that cluster of anxiety disorders. Yet there is a dearth of studies examining whether early separation anxiety is inherited. The present twin study, based on a retrospective approach, revealed a substantial genetic contribution to separation anxiety in females but not in males, with unique environmental influences being important in both gender groups. Although speculative, an evolutionary explanation is offered to account for the apparent gender difference in the inheritance of early separation anxiety. It is hypothesized that, in some women, phylogenetic vestiges of separation anxiety may conflict with their need to compete in an individualistic manner in the modern workplace. Whether such an attachment-autonomy conflict accounts for the increased rate of panic disorder and agoraphobia in women is worthy of further study.

The prevalence of major anxiety disorders in relatives of alcohol dependent men and women

OBJECTIVE

The relationship between alcohol dependence and lifelong major anxiety disorders is complex. The literature indicates a close association between anxiety symptoms and drinking behavior. However, it is difficult to determine whether the anxiety conditions are lifelong disorders or if they represent temporary organic conditions related to alcohol intoxication and withdrawal. One approach to understanding more about the relationships between alcohol dependence and major anxiety disorders is to observe the rate of anxiety-related diagnoses in close relatives of alcoholics. This approach evaluates whether alcoholism and major anxiety disorders might share a common genetic basis.

METHOD

The data presented here describe the rates of four major anxiety disorders in 591 interviewed first-degree relatives of alcohol dependent men and women. The data were gathered through face-to-face structured standardized interviews.

RESULTS

The analyses reveal that after focusing on DSM-III-R anxiety disorders, controlling for the potential presence of temporary organic conditions in the subject and considering the impact of assortative mating in their parents, the life-time risk for panic disorder in close biological family members of alcoholics is 3.4%; for agoraphobia, 1.4%; for social phobia, 2.3%; and for obsessive-compulsive disease, 1.4%.

CONCLUSIONS

These data do not indicate an exceptionally high rate of anxiety disorders among close relatives of alcoholics. While other mechanisms might contribute to relationship between alcoholism and major anxiety disorders, the results do not support evidence of a common genotype for the two disorders.

Major depression and phobias: the genetic and environmental sources of comorbidity

In a population based sample of 2163 personally interviewed female twins, substantial comorbidity was observed between DSM-III-R defined major depression (MD) and 4 subtypes of phobia: agoraphobia, social phobia, animal phobia and situational phobia. However, the level of comorbidity of MD with agoraphobia was much greater than that found with the other phobic subtypes. We concluded bivariate twin analyses to decompose the genetic and environmental sources of comorbidity between MD and the phobias. Our results suggest that a modest proportion of the genetic vulnerability to MD also influences the risk for all phobic subtypes, with the possible exception of situational phobias. Furthermore, the magnitude of comorbidity resulting from this shared genetic vulnerability is similar across the phobic subtypes. By contrast, the non-familial environmental experiences which predispose to depression substantially increase the vulnerability to agoraphobia, have a modest impact on the risk for social and situational phobias and no effect on the risk for animal phobias. The increased comorbidity between MD and agoraphobia results, nearly entirely, from individual-specific environmental risk factors for MD which also increase the risk for agoraphobia but not for other phobias.

A controlled family study in panic disorder

There are only a few family studies in panic disorder. Although there is some evidence that panic disorder is familial, the exact figures of the familial risk for this disorder are at variance across different studies; the impact of comorbidity and of the gender of relatives is also unclear. Family studies in panic disorder controlling for the comorbidity in probands are therefore indicated. This study presents the morbid risks in families of 40 "pure" panic disorder probands (DSM-III-R) without a history of psychotic disorders, major depression or alcoholism compared with families of 80 controls recruited in the general population. The relative frequency of panic disorder (DSM-III-R) in the first-degree relatives of panic disorder probands was 5.7% (the age corrected morbid risk is 7.9%) compared to 1.8% in relatives of healthy controls (age corrected morbid risk 2.3%). Agoraphobia segregated predominantly among female relatives of agoraphobic probands. An increased familial risk of major depression and of alcoholism was also observed. Comorbidity with alcoholism and major affective disorders was excluded in panic disorder probands by definition; therefore, these findings indicate that the etiological factors underlying panic disorder may overlap with those of alcoholism and those of unipolar major depression.

Anxiety disorders in the joint hypermobility syndrome

A case-control study was designed to test the association between joint hypermobility syndrome (JHS), an inherited disorder of collagen synthesis, and anxiety and phobic disorders. One hundred fourteen cases of JHS diagnosed at the rheumatology outpatient clinic of the Hospital del Mar (Barcelona) were compared to 59 control subjects randomly selected from patients seen at the same clinic. Both cases and controls were examined by a psychologist who used the Structured Clinical Interview for DSM-III-R and who was unaware of their medical diagnoses. DSM-III-R diagnoses of panic disorder, agoraphobia, and simple phobia, but not generalized anxiety disorder, dysthymic disorder, or major depression were found to be highly associated with JHS (age- and sex-adjusted odds ratio = 10.7). Mitral valve prolapse (MVP) was present only among JHS cases. Among cases of JHS, subjects with MVP were almost three times more likely to suffer from anxiety than subjects without MVP (odds ratio = 2.95), although the association was not statistically significant. The strong association between panic anxiety and JHS appears to occur at a higher level than the association between panic and MVP, and provides a new basis for further studies on the genetic background of panic-anxiety.

Family genetic studies of panic disorder

A review of family and twin studies using specified diagnostic criteria shows the highly familial nature of panic disorder and suggests evidence for a genetic etiology. The population-based lifetime rates of panic disorder cross-nationally range between 1.2/100 and 2.4/100, whereas, the lifetime rates in first-degree relatives of panic probands range between 7.7/100 and 20.5/100. There is evidence from family and twin studies for the separation of panic disorder and generalized anxiety disorder. While there is a substantial comorbidity in individuals between panic disorder and major depression, these two disorders are separate conditions which are independently and specifically transmitted within families. The mode of transmission of panic disorder remains unclear. The high lifetime rates of panic disorder, strong evidence for vertical transmission, and the potential biological markers have increased interest in the application of modern linkage techniques. Several genetic linkage studies of panic disorder are ongoing.

Mental health locus of control in first-degree relatives of agoraphobic and depressed inpatients

Mental health locus of control in 77 first-degree relatives of agoraphobic, agoraphobic and major depressed (comorbid), and depressed inpatients were studied. Relatives of comorbid patients externalized locus of control more to chance than did relatives of agoraphobic and of depressed patients. These results suggest that a tendency to externalize to chance is familially transmitted and may be a vulnerability factor for the development of the comorbid condition of agoraphobia and major depression.