Association of rs7688285 allelic variation coding for GLRB with fear reactivity and exposure-based therapy in patients with panic disorder and agoraphobia

The gene coding for glycine receptor β subunits (GLRB) has been found to be related to panic disorder and agoraphobia (PD/AG) and to be associated with altered insular BOLD activation during fear conditioning, as an intermediate phenotype of defensive system reactivity in healthy subjects. In a multicenter clinical trial on PD/AG patients we investigated in three sub-samples whether GLRB allelic variation (A/G; A-allele identified as «risk») in the single nucleotide polymorphism rs7688285 was associated with autonomic (behavioral avoidance test BAT; n = 267 patients) and neural (differential fear conditioning; n = 49 patients, n = 38 controls) measures, and furthermore with responding towards exposure-based cognitive behavioral therapy (CBT, n = 184 patients). An interaction of genotype with current PD/AG diagnosis (PD/AG vs. controls; fMRI data only) and their modification after CBT was tested as well. Exploratory fMRI results prior to CBT, revealed A-allele carriers irrespective of diagnostic status to show overall higher BOLD activation in the hippocampus, motor cortex (MC) and insula. Differential activation in the MC, anterior cingulate cortex (ACC) and insula was found in the interaction genotype X diagnosis. Differential activation in ACC and hippocampus was present in differential fear learning. ACC activation was modified after treatment, while no overall rs7688285 dependent effect on clinical outcomes was found. On the behavioral level, A-allele carriers showed pronounced fear reactivity prior to CBT which partially normalized afterwards. In sum, rs7688285 variation interacts in a complex manner with PD/AG on a functional systems level and might be involved in the development of PD/AG but not in their treatment.

The structure of genetic and environmental risk factors for fears and phobias

BACKGROUND

Although prior genetic studies of interview-assessed fears and phobias have shown that genetic factors predispose individuals to fears and phobias, they have been restricted to the DSM-III to DSM-IV aggregated subtypes of phobias rather than to individual fearful and phobic stimuli.

METHOD

We examined the lifetime history of fears and/or phobias in response to 21 individual phobic stimuli in 4067 personally interviewed twins from same-sex pairs from the Virginia Adult Twin Study of Psychiatric and Substance Abuse Disorders (VATSPSUD). We performed multivariate statistical analyses using Mx and Mplus.

RESULTS

The best-fitting model for the 21 phobic stimuli included four genetic factors (agora-social-acrophobia, animal phobia, blood-injection-illness phobia and claustrophobia) and three environmental factors (agora-social-hospital phobia, animal phobia, and situational phobia).

CONCLUSIONS

This study provides the first view of the architecture of genetic and environmental risk factors for phobic disorders and their subtypes. The genetic factors of the phobias support the DSM-IV and DSM-5 constructs of animal and blood-injection-injury phobias but do not support the separation of agoraphobia from social phobia. The results also do not show a coherent genetic factor for the DSM-IV and DSM-5 situational phobia. Finally, the patterns of co-morbidity across individual fears and phobias produced by genetic and environmental influences differ appreciably.

Higher-order genetic and environmental structure of prevalent forms of child and adolescent psychopathology

CONTEXT

It is necessary to understand the etiologic structure of child and adolescent psychopathology to advance theory and guide future research.

OBJECTIVE

To test alternative models of the higher-order structure of etiologic effects on 11 dimensions of child and adolescent psychopathology using confirmatory factor analyses of genetic and environmental covariances.

DESIGN

Representative sample of twins.

SETTING

Home interviews.

PARTICIPANTS

A total of 1571 pairs of 9- to 17-year-old twins.

MAIN OUTCOME MEASURES

Structured assessments of psychopathology using adult caregivers and youth as informants.

RESULTS

The best-fitting genetic model revealed that most genetic factors nonspecifically influence risk for either all 11 symptom dimensions or for dimensions of psychopathology within 1 of 2 broad domains. With some notable exceptions, dimension-specific genetic influences accounted for modest amounts of variance.

CONCLUSIONS

To inform theory and guide molecular genetic studies, an etiologic model is offered in which 3 patterns of pleiotropy are hypothesized to be the principal modes of genetic risk transmission for common forms of child and adolescent psychopathology. Some common environmental influences were found, but consistent with a "generalist genes, specialist environments" model, there was little sharing of environmental influences. This implies that prevalent dimensions of child and adolescent psychopathology mostly share their genetic liabilities but are differentiated by nonshared experiences.

Adenosine A(2A) receptor gene: evidence for association of risk variants with panic disorder and anxious personality

Adenosine A(2A) receptors are suggested to play an important role in different brain circuits and pathways involved in anxiety reactions. A variant within the corresponding ADORA2A gene (rs5751876) increased the risk for panic disorder (PD), for elevated anxiety during challenge tests in healthy probands and for anxiety-related arousal in blood-injury phobia. These multiple effects may mirror a more general effect of the SNP on basic personality traits. In the present study we therefore aimed to replicate the original finding in a large PD sample and extend it by investigating an additional proband sample characterized for different anxiety-related personality scores. In addition, as rs5751876 is assumed not to be the disease variant itself but to be in linkage disequilibrium (LD) with the true functional polymorphism other SNPs of potentially functional relevance were identified by re-sequencing the whole gene including several newly identified regions of putative regulatory potential and analysed for their impact on PD and anxious personality. We were indeed able to replicate rs5751876 as risk factor for PD, particularly PD with agoraphobia. Rs5751876 and several other variants in high LD (rs5751862, rs2298383 and rs3761422) as well as the corresponding haplotypes were also associated with different anxiety-related personality scores (Bonferroni corrected P(all) < 0.05). Of these variants, rs2298383 shows functional potential based on in silico analyses and might therefore represent the true underlying causal variant. Our data provide further support for an important role of ADORA2A variants in the pathogenesis of anxiety disorders and anxious personality reflecting their potential as basic susceptibility factors.

The role of fear and anxiety in the familial risk for major depression: a three-generation study

BACKGROUND

The overlap between anxiety and major depressive disorder (MDD), the increased risk for depression and anxiety in offspring of depressed parents, the sequence of onset with anxiety preceding MDD, and anxiety as a predictor of depression are well established. The specificity of anxiety disorders in these relationships is unclear. This study, using a longitudinal high-risk design, examined whether anxiety disorders associated with the emotions fear and anxiety mediate the association between parental and offspring depression.

METHOD

Two hundred and twenty-four second-generation and 155 third-generation descendants at high and low risk for depression because of MDD in the first generation were interviewed over 20 years. Probit and Cox proportional hazard models were fitted with generation 2 (G2) or G3 depression as the outcome and parental MDD as the predictor. In G2 and G3, fear- (phobia or panic) and anxiety-related [overanxious or generalized anxiety disorder (GAD)] disorders were examined as potential mediators of increased risk for offspring depression, due to parental MDD.

RESULTS

In G2, fear-related disorders met criteria for mediating the association between parental MDD and offspring MDD whereas anxiety-related disorders did not. These results were consistent, regardless of the analytic methods used. Further investigation of the mediating effect of fear-related disorders by age of onset of offspring MDD suggests that the mediating effect occurs primarily in adolescent onset MDD. The results for G3 appear to follow similar patterns.

CONCLUSIONS

These findings support the separation of anxiety disorders into at least two distinct forms, particularly when examining their role in the etiology of depression.

A genetic study of the acute anxious response to carbon dioxide stimulation in man

People with panic disorder-agoraphobia and their relatives often react anxiously to CO(2)-enriched gas mixtures. Available data are not suited to disentangle genetic from common environmental causes of familial aggregation of CO(2) reactivity, nor provide quantitative estimations of the sources of trait variation. Three-hundred-forty-six twin pairs belonging to the general population-based Norwegian NIPH Mental Health Study underwent self-assessments of anxiety and of DSM-IV panic symptoms after inhalation of a 35%CO(2)-65%O(2) mixture. Two thresholds were employed - at sample's 75th and 90th percentiles of responses - to define provoked panic attacks and to calculate polychoric correlations. Variance components were estimated by structural equation modelling (SEM). For definitions of responses based on the sum of all 13 panic symptoms, SEM could not discriminate between shared environmental versus genetic causes of familial resemblance for provoked attacks. For definitions of responses based on global anxiety, or on the sums of those symptoms (dyspnea, dizziness, palpitations) with highest variance post-CO(2), the best-fitting models indicated additive genetic factors as the sole causes for within-family resemblance. Best-fit heritability estimates ranged from 0.42 to 0.57. Genetic and idiosyncratic environmental factors explain most of individual differences in reactivity to hypercapnia. Within-family similarities for this trait are largely explained by genetic determinants.

Association of a Met88Val diazepam binding inhibitor (DBI) gene polymorphism and anxiety disorders with panic attacks

Several lines of evidence suggest that anxiety disorders have a strong genetic component, but so far only few susceptibility genes have been identified. There is preclinical and clinical evidence for a dysregulation of the central gamma-aminobutyric acid (GABA)-ergic tone in the pathophysiology of anxiety disorders. Diazepam binding inhibitor (DBI) has been suggested to play a pivotal role in anxiety disorders through direct and indirect, i.e. via synthesis of neuroactive steroids, modulation of GABA(A) receptor function. These findings suggest that the DBI gene can be postulated as a candidate for a genetic association study in this disorder. Thus, single nucleotide polymorphisms (SNPs) of the DBI gene were investigated for putative disease associations in a German sample of anxiety disorder patients suffering from panic attacks and matched controls. We were able to detect a significant association between a non-synonymous coding variant of DBI with anxiety disorders with panic attacks. The rare allele of this polymorphism was more frequent in controls than in patients (OR=0.43; 95% CI: 0.19-0.95). In conclusion, these results suggest a central role of DBI genetic variants in the susceptibility for the development of anxiety disorders that are characterized by the occurrence of panic attacks.

Association of polymorphisms in P2RX7 and CaMKKb with anxiety disorders

BACKGROUND

There is considerable evidence that genetic factors play an important role in the pathophysiology of affective disorders including bipolar disorder, major depressive disorder and anxiety disorders. Long-term follow up studies as well as drug treatment studies suggest that these clinical conditions share a number of pathophysiological commonalities including genetic variables. One possible candidate region is located on chromosome 12q24.31, originated from previous linkage and association studies with bipolar disorder and unipolar depression. This region contains two candidate genes for purinergic ligand-gated ion channels, P2RX7 and P2RX4, and one gene coding for calmodulin-dependent protein kinase kinase b (CaMKKb).

METHODS

In the present study, we investigated the genetic associations between 15 SNPs in the candidate genes P2RX7, P2RX4 and CaMKKb on chromosome 12q24.31 in 179 patients with anxiety disorders and syndromal panic attacks versus 462 healthy controls.

RESULTS

One nominal case-control association could be detected for a SNP in the 5'UTR region of P2RX4, which did not remain significant after correction for multiple testing. We found, however, a prominent association between severity of panic- and agoraphobia symptoms and an exonic SNP (rs3817190) in the CaMKKb gene and a trend for association with an exonic SNP in P2RX7 (rs1718119) with severity scores in the panic- and agoraphobia scale.

CONCLUSION

The locus 12q24.31 seems to be an important genetic region for anxiety, bipolar and unipolar disorders, suggesting a genetic overlap in the group of affective disorders. The specific contribution of the herein reported gene polymorphisms to the clinical condition is still unclear and warrants further analysis.

Effects of parental anxiety disorders in children at high risk for panic disorder: a controlled study

BACKGROUND

To examine the association between anxiety disorders in parents and offspring in a sample of children at risk for panic disorder. We hypothesized that individual anxiety disorders will breed true in offspring.

METHODS

Comparisons were made between offspring of parents with PD+MD (N=136), PD (N=27), MD (N=27), and Controls (N=103). All subjects were assessed with structured diagnostic interviews. Individual anxiety disorders in the offspring were used as dependent variables in logistic regression models where parental PD status, parental MD, and the same parental anxiety diagnosis were used as independent binary variables.

RESULTS

Social phobia and separation anxiety disorder in the offspring were accounted for by the same disorders in the parent, whereas agoraphobia and OCD in the offspring were accounted for by parental panic disorder.

CONCLUSIONS

These findings suggest that differing risk factors underlie the expression of individual anxiety disorders in children at risk for panic disorder.

The novel brain-specific tryptophan hydroxylase-2 gene in panic disorder

Panic disorder is a common psychiatric disorder characterized by recurrent anxiety attacks and anticipatory anxiety. Due to the severity of the symptoms of the panic attacks and the frequent additional occurrence of agoraphobia, panic disorder is an often debilitating disease. Elevation of central serotonin levels by drugs such as clomipramine represents one of the most effective treatment options for panic disorder. This points to an important role of dysregulation of the serotonergic system in the genetic etiology of panic disorder. The novel brain-specific 5-HT synthesizing enzyme, tryptophan hydroxylase-2 (TPH2), which represents the rate-limiting enzyme of 5-HT production in the brain, may therefore be of particular importance in panic disorder. We focused on the putative transcriptional control region of TPH2 and identified two novel common single nucleotide polymorphisms (SNPs) of TPH2 in and close to this region. Moreover, a recently described loss-of-function mutation of TPH2 which results in an 80% reduction of serotonin production, was assessed. In an analysis of the putative transcriptional control region SNPs in a sample of panic disorder patients and controls no association of the disorder with the TPH2 SNPs or haplotypes was found. Moreover, the loss-of-function R441H mutation of TPH2 was not present in the panic disorder patients. The results of this first study of TPH2 in panic disorder argue against an importance of allelic variation of TPH2 in the pathogenesis of panic disorder with or without agoraphobia.

Affective disorder in the parents of a clinic sample of children with anxiety disorders

BACKGROUND

Family history studies in adults reveal strong familiality for the anxiety disorders with some specificity. The aim of the current study was to establish whether there was an elevated rate of anxiety disorders in the parents of children with anxiety disorders, and whether there was intergenerational specificity in the form of disorder.

METHODS

The mental state of a clinic sample of 85 children with anxiety disorder and their parents was systematically assessed, together with a comparison sample of 45 children with no current disorder and their parents.

RESULTS

Compared to the rate of anxiety disorder amongst parents of comparison children, the rate of current anxiety disorder in mothers of anxious children was significantly raised, as was the lifetime rate of anxiety disorder for both mothers and fathers. The mothers of children with generalised anxiety disorder, social phobia, specific phobia and separation anxiety disorder all had raised lifetime rates of the corresponding disorder, but also raised rates of others disorders.

LIMITATIONS

Only 60% of the fathers of the anxious children were assessed.

CONCLUSIONS

Strong familiality of anxiety disorders was confirmed, especially between child and maternal anxiety disorder. All child anxiety disorders were associated with several forms of anxiety disorder in the mother. Some specificity in the form of anxiety disorder in the child and the mother was apparent for social phobia and separation anxiety disorder. The findings have implications for the management of child anxiety.

Generalized anxiety disorder: What are we missing?

One of the most prevalent anxiety conditions seen in primary care is generalized anxiety disorder (GAD). Numerous physical ailments frequently accompany the psychic symptoms of anxiety, which often drive patients to ask for help. In spite of the high incidence of GAD, only 30% of sufferers are diagnosed. Furthermore, very few patients are prescribed medication or referred to a psychiatrist. The key aim is to ensure the early detection and management of these patients. Developing physician education programs may improve the identification of GAD. The use of simple diagnostic tools would also aid the early detection of sufferers. Physicians require more long-term data, including that on the influence of ethnicity and genetics, to assist them to better understand and more effectively manage GAD. By achieving early diagnosis and treatment of GAD, physicians can ensure that a lesser burden is inflicted upon sufferers, thus improving their quality of life.

Rgs 2 gene polymorphisms as modulators of anxiety in humans?

Rgs2 (regulator of G-protein signalling 2) gene recently was reported as a quantitative trait gene for anxious behaviour in mice and male Rgs2 knockout mice have been shown to be more anxious than wildtype mice. Therefore we investigated four non-coding single nucleotide polymorphisms in a sample of 173 patients with panic disorder and 173 matched controls of German descent. At the genotype level all four SNPs were associated with panic disorder (p = 0.02-0.05). At the haplotype level the strongest association was observed for a haplotype containing SNP3 and SNP 4 (subgroup men and men with agoraphobia: p = 0.01 and 0.03). This points towards a functional polymorphism at the 3' end of the gene. Our results support the hypothesis that variations of the Rgs2 gene play a role also for the development of anxiety in humans.

The value of four mental health self-report scales in predicting interview-based mood and anxiety disorder diagnoses in sibling pairs

Questionnaire-based dimensional measures are often employed in epidemiological studies to predict the presence of psychiatric disorders. The present study sought to determine how accurately 4 dimensional mental health measures, the 12-item General Health Questionnaire (GHQ-12), Neuroticism (EPQ-N), the high positive affect and anxious arousal scales from the Mood and Anxiety Symptoms Questionnaire (MASQ-HPA and MASQ-AA) and a composite of all 4, predicted psychiatric caseness as diagnosed by the University of Michigan Composite International Diagnostic Interview (UM-CIDI). Community subjects were recruited through general practitioners; those who agreed to participate were sent a questionnaire containing the above measures. Subsequently, the UM-CIDI was administered by telephone to 469 subjects consisting of sibling pairs who scored most discordantly or concordantly on a composite index of the 4 measures. Logistic Regression and Receiver Operating Characteristic (ROC) curve analyses were carried out to assess the predictive accuracy of the dimensional measures on UM-CIDI diagnosis. A total of 179 subjects, 62 men and 117 women with an average age of 42 years, were diagnosed with at least one of the following psychiatric disorders: depression, dysthymia, generalized anxiety disorder (GAD), social phobia, agoraphobia and panic attack. The six disorders showed high comorbidity. EPQ-N and the Composite Index were found to be very strong and accurate predictors of psychiatric caseness; they were however unable to differentiate between specific disorders. The results from the present study therefore validated the four mental health measures as being predictive of psychiatric caseness.

No association of the brain-derived neurotrophic factor (BDNF) gene polymorphisms with panic disorder

Several lines of evidence suggest that genetic factors might contribute to susceptibility to panic disorder. Our previous studies show that the brain-derived neurotrophic factor (BDNF) may play a role in the pathophysiology of major depressive disorders and eating disorders. Assuming that BDNF may be implicated in the putative common pathophysiology of depression and anxiety, we analyzed the association of two BDNF gene single nucleotide polymorphisms (SNPs), 132C > T (formerly named C270T) in the noncoding region of exon V and 196G > A (val66met) in the coding region of exon XIIIA, with panic disorder. In this study, 109 patients with panic disorder diagnosed according to the DSM-IV criteria, and 178 control subjects were recruited. There were no significant differences in the frequency of the genotype or allele in these two SNPs between patients and controls [132C > T in exon V: genotype, p = 1.0, allele, p = 0.59; 196G > A (val66met) in exon XIIIA: genotype, p = 0.77, allele, p = 0.78]. Furthermore, no significant associations of agoraphobia with the two SNPs were detected. This study suggests that the BDNF gene polymorphisms are not associated with panic disorder in our Japanese population.

Agoraphobic behavior and panic attack: a study of male twins

We used data from 3372 pairs of male twins from the Vietnam Era Twin Registry to examine comorbidity and familial influences on the frequently observed association between agoraphobic behavior and panic. Due to low prevalence of DSM-III-R-defined panic disorder, we also examined subjects who had experienced at least one panic attack during their lives. Agoraphobic behavior among individuals with a history of panic attacks showed familial aggregation (odds ratio = 5.7; P = .018 ). Probands with panic attacks and agoraphobic behavior and their co-twins had higher risk of major depression than probands without agoraphobic avoidance and their co-twins (P = .01). Groups did not differ for alcohol dependence or antisocial personality. Agoraphobic behavior associated with panic attack is familial and associated with comorbid major depression. Agoraphobia following panic attack does not seem to reflect severity as agoraphobic behavior in the proband was unrelated to risk of panic attacks in the co-twin.

Norepinephrine transporter (NET) promoter and 5'-UTR polymorphisms: association analysis in panic disorder

Several biochemical and pharmacological studies suggest that the catecholaminergic system involving the norepinephrine transporter (NET) is relevant for the pathogenesis of panic disorder. Three single nucleotide polymorphisms in the promoter or untranslated 5' region of the NET gene were investigated by means of RFLP analysis in a sample of 115 German patients with panic disorder and 115 matched controls. Statistical analysis failed to show association with the overall diagnosis of panic disorder. In the subgroup of patients with panic disorder without agoraphobia, however, two polymorphisms were found to be associated with the disease (G/C (rs2397771): p < 0.05; T/C (rs2242446): p < 0.01). While our data do not support a major function of the NET gene in the development of panic disorder, it may play a role in the subgroup of panic disorder without agoraphobia.

Does referral bias impact findings in high-risk offspring for anxiety disorders? A controlled study of high-risk children of non-referred parents with panic disorder/agoraphobia and major depression

BACKGROUND

Previous findings in referred samples documented significant diagnostic specificity in patterns of transmission between parents with panic disorder (PD) and parents with major depression (MD) and their offspring. This study evaluated whether these patterns of transmission between parents and high-risk offspring are moderated by referral bias.

METHODS

Parental PD/agoraphobia (AG) and parental MD were used to predict rates of offspring psychiatric disorders and functional outcomes using data from an opportunistic sample of parents (n = 991) and offspring (n = 734) ascertained from case-control family genetic studies of youth with and without attention-deficit hyperactivity disorder. Subjects were comprehensively assessed with structured diagnostic interview methodology to evaluate psychiatric disorders in parents and offspring.

RESULTS

Parental PD/AG increased the risk for anxiety disorders in offspring, independently of parental MD while parental MD increased the risk for mood and disruptive behavior disorders in offspring, independently of parental PD/AG. Parental psychopathology was also associated with functional impairment in offspring.

LIMITATIONS

The use of a sample ascertained by ADHD and control probands, and parent psychiatric diagnostic reports for children under 12.

CONCLUSIONS

These results extend to non-referred samples previous findings from referred samples documenting diagnostic specificity in the familial transmission of PD/AG and MD from parents to offspring, suggesting that these patterns of transmission are not due to referral bias. These results could inform and enhance community programs aimed at screening for and treating pediatric psychopathology.

Association study of a brain-derived neurotrophic factor (Val66Met) genetic polymorphism and panic disorder

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophic factor family, plays an important role in the development, maintenance and function of several neuronal systems. Recent studies have demonstrated that antidepressants, commonly used for panic disorder treatment, can increase central BDNF. In addition, animals with BDNF deficits have higher levels of anxiety when exposed to stressors in comparison to normal controls. The present study tested the hypothesis that the BDNF gene Val66Met polymorphism is associated with panic disorder. In this study, therefore, the incidence of this polymorphism was compared in 103 panic disorder patients and 180 normal controls. The genotype and allele frequencies for the BDNF gene Val66Met polymorphism did not differ comparing the two groups. Furthermore, no association was demonstrated between this BDNF polymorphism and either mitral valve prolapse or agoraphobia in panic disorder patients. These findings suggest that the investigated BDNF polymorphism does not play a major role in the pathogenesis of panic disorder in this Chinese population. Further studies exploring the relationship between genetic variations of BDNF and the cerebral atrophy associated with, and antidepressant treatment response in, panic disorder may be appropriate.

Association of a functional 1019C>G 5-HT1A receptor gene polymorphism with panic disorder with agoraphobia

Panic disorder is a common anxiety disorder which frequently co-occurs with agoraphobia. A functional promoter polymorphism in the serotonin receptor 1A (5-HT1A) gene has been found to be associated with major depression as well as anxiety- and depression-related personality traits. We investigated a possible association between this 5-HT1A gene promoter polymorphism and panic disorder by genotyping the 1019C>G single nucleotide polymorphism in 134 panic-disorder patients with and without agoraphobia and matched 134 controls. In our sample no significant evidence of allelic association in the combined panic-disorder group was found. However, our results show a significant association with the G allele in patients with panic disorder with agoraphobia (p=0.03, n=101). In conclusion, our findings do not support a major contribution of this polymorphism to the pathogenesis of panic disorder, but provide evidence for a possible role in the subgroup with agoraphobia.

Failure to find DUP25 in patients with anxiety disorders, in control individuals, or in previously reported positive control cell lines

Investigation of the co-occurrence of panic and phobic disorders with joint laxity led to the identification of various forms of interstitial duplications involving human chromosome 15q24-q26 (named "DUP25") in a Spanish population. DUP25 was observed in 68 of 70 (97%) patients assigned the diagnosis panic disorder/agoraphobia. DUP25 was also found in 14 of 189 (7%) control individuals. In the present study, we replicated the experimental conditions described by Gratacòs and colleagues in which fluorescence in situ hybridization was used to examine metaphase chromosomes of patients with panic disorder/social phobia and of control individuals from a southern region of the United Kingdom, the primary aim being to determine the prevalence of this chromosomal rearrangement in a geographically and ethnically distinct population. DUP25 was not observed in any of our 16 patients or 40 control samples or in three previously reported DUP25-positive control (Centre d'Etude du Polymorphisme Humain) cell lines, indicating a highly significant difference in the frequency of DUP25 between the study by Gratacòs and colleagues and the present investigation.

Human nuclear transcription factor gene CREM: genomic organization, mutation screening, and association analysis in panic disorder

Panic disorder is an anxiety disorder with an estimated heritability of 48%. Variation in the gene of the nuclear transcription factor "cAMP-responsive element modulator" (CREM) might contribute to its pathogenesis. CREM knock-out mice exhibit significantly less anxiety behavior than wild-type mice and the alternative CREM gene product "inducible cAMP early repressor" (ICER) plays a pivotal role in the hypothalamo-pituitary-adrenal (HPA) axis, which is disturbed in panic disorder. We characterized the genomic organization of the human CREM gene and performed a systematic mutation screening by means of single stranded conformational analysis (SSCA) in a sample of 40 German patients with panic disorder (DSM-III-R). Four novel single nucleotide polymorphisms in CREM promoters P 1 and P 4, one trinucleotide (ATT)-repeat polymorphism in CREM promoter P 2-generating the ICER isoform-and a rare amino acid substitution in CREM exon glut 2 were identified. Association analysis in an extended sample of German patients (n = 88) revealed a significant excess of the shorter CREM P 2 promoter eight-repeat trinucleotide allele and of genotypes containing the eight-repeat trinucleotide allele in panic disorder (P = 0.02), in particular in panic disorder without agoraphobia (P = 0.001). A replication study in independent Italian (n = 76) and Spanish (n = 62) samples, however, failed to confirm this observation. This suggests that the CREM P 2 promoter trinucleotide polymorphism is not a major susceptibility factor in the pathogenesis of panic disorder. Functional analysis of the observed CREM P 2 promoter polymorphism as well as studies in independent panic disorder samples are necessary.

Catechol O-methyltransferase genetic polymorphism in panic disorder

OBJECTIVE

The authors examined the distribution of catechol O-methyltransferase (COMT) genotypes in patients with panic disorder as well as the relationship between a COMT polymorphism and the clinical characteristics of these patients.

METHOD

Fifty-one patients with panic disorder and 45 healthy comparison subjects were tested for a genetic polymorphism of COMT. Clinical variables were assessed for the patients with panic disorder.

RESULTS

The frequency of the L/L genotype was significantly higher in the patients with panic disorder than in the healthy subjects (19.6% versus 2.2%). Panic disorder was significantly associated with the L allele and L/L genotype. Patients with panic disorder who had the L/L genotype showed poorer treatment response than those with other genotypes.

CONCLUSIONS

These results suggest that the L/L genotype of the COMT gene may be related to the development and treatment outcome of panic disorder in some patients.

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.