GLRB allelic variation associated with agoraphobic cognitions, increased startle response and fear network activation: a potential neurogenetic pathway to panic disorder.

The molecular genetics of panic disorder (PD) with and without agoraphobia (AG) are still largely unknown and progress is hampered by small sample sizes. We therefore performed a genome-wide association study with a dimensional, PD/AG-related anxiety phenotype based on the Agoraphobia Cognition Questionnaire (ACQ) in a sample of 1370 healthy German volunteers of the CRC TRR58 MEGA study wave 1. A genome-wide significant association was found between ACQ and single non-coding nucleotide variants of the GLRB gene (rs78726293, P=3.3 × 10-8; rs191260602, P=3.9 × 10-8). We followed up on this finding in a larger dimensional ACQ sample (N=2547) and in independent samples with a dichotomous AG phenotype based on the Symptoms Checklist (SCL-90; N=3845) and a case-control sample with the categorical phenotype PD/AG (Ncombined =1012) obtaining highly significant P-values also for GLRB single-nucleotide variants rs17035816 (P=3.8 × 10-4) and rs7688285 (P=7.6 × 10-5). GLRB gene expression was found to be modulated by rs7688285 in brain tissue, as well as cell culture. Analyses of intermediate PD/AG phenotypes demonstrated increased startle reflex and increased fear network, as well as general sensory activation by GLRB risk gene variants rs78726293, rs191260602, rs17035816 and rs7688285. Partial Glrb knockout mice demonstrated an agoraphobic phenotype. In conjunction with the clinical observation that rare coding GLRB gene mutations are associated with the neurological disorder hyperekplexia characterized by a generalized startle reaction and agoraphobic behavior, our data provide evidence that non-coding, although functional GLRB gene polymorphisms may predispose to PD by increasing startle response and agoraphobic cognitions.

Allelic variation in CRHR1 predisposes to panic disorder: evidence for biased fear processing.

Corticotropin-releasing hormone (CRH) is a major regulator of the hypothalamic-pituitary-adrenal axis. Binding to its receptor CRHR1 triggers the downstream release of the stress response-regulating hormone cortisol. Biochemical, behavioral and genetic studies revealed CRHR1 as a possible candidate gene for mood and anxiety disorders. Here we aimed to evaluate CRHR1 as a risk factor for panic disorder (PD). Allelic variation of CRHR1 was captured by 9 single-nucleotide polymorphisms (SNPs), which were genotyped in 531 matched case/control pairs. Four SNPs were found to be associated with PD, in at least one sub-sample. The minor allele of rs17689918 was found to significantly increase risk for PD in females after Bonferroni correction and furthermore decreased CRHR1 mRNA expression in human forebrains and amygdalae. When investigating neural correlates underlying this association in patients with PD using functional magnetic resonance imaging, risk allele carriers of rs17689918 showed aberrant differential conditioning predominantly in the bilateral prefrontal cortex and safety signal processing in the amygdalae, arguing for predominant generalization of fear and hence anxious apprehension. Additionally, the risk allele of rs17689918 led to less flight behavior during fear-provoking situations but rather increased anxious apprehension and went along with increased anxiety sensitivity. Thus reduced gene expression driven by CRHR1 risk allele leads to a phenotype characterized by fear sensitization and hence sustained fear. These results strengthen the role of CRHR1 in PD and clarify the mechanisms by which genetic variation in CRHR1 is linked to this disorder.

Dimensional structure of bodily panic attack symptoms and their specific connections to panic cognitions, anxiety sensitivity and claustrophobic fears.

BACKGROUND: Previous studies of the dimensional structure of panic attack symptoms have mostly identified a respiratory and a vestibular/mixed somatic dimension. Evidence for additional dimensions such as a cardiac dimension and the allocation of several of the panic attack symptom criteria is less consistent. Clarifying the dimensional structure of the panic attack symptoms should help to specify the relationship of potential risk factors like anxiety sensitivity and fear of suffocation to the experience of panic attacks and the development of panic disorder. METHOD: In an outpatient multicentre study 350 panic patients with agoraphobia rated the intensity of each of the ten DSM-IV bodily symptoms during a typical panic attack. The factor structure of these data was investigated with nonlinear confirmatory factor analysis (CFA). The identified bodily symptom dimensions were related to panic cognitions, anxiety sensitivity and fear of suffocation by means of nonlinear structural equation modelling (SEM). RESULTS: CFA indicated a respiratory, a vestibular/mixed somatic and a cardiac dimension of the bodily symptom criteria. These three factors were differentially associated with specific panic cognitions, different anxiety sensitivity facets and suffocation fear. CONCLUSIONS: Taking into account the dimensional structure of panic attack symptoms may help to increase the specificity of the associations between the experience of panic attack symptoms and various panic related constructs.

Effects of stress and relaxation on pain perception in subjects with pain-free occlusional disharmony compared with healthy controls.

OBJECTIVES: The significance of occlusal disharmony for the development of painful temporomandibular disorder (TMD) is controversial. The ongoing biomechanical strain caused by occlusal disharmony might lead to sensitization processes in the nociceptive system. Understanding these processes might be an important step toward understanding the possible relationship between occlusal disharmony and TMD. In this study, we therefore investigated whether subjects with occlusal disharmony (n = 22) differ from healthy controls (n = 26) in their pain perception and pain modulation by stress and relaxation. MATERIALS AND METHODS: Trigeminal and extratrigeminal experimental pain perception (pinprick, heat, and pressure pain) was assessed before and after stress (mental arithmetic) and relaxation (viewing of low-arousal pictures). RESULTS: There were no group differences in pain perception at baseline or during the stress task. Compared with controls, the occlusal disharmony group exhibited an inadequate reduction in pain perception during relaxation, which was significant for the extratrigeminal site (P < 0.01) and reached a trend for significance at the trigeminal site (P = 0.1). CONCLUSIONS: These results suggest that subjects with occlusal disharmony show signs of disturbed endogenous pain inhibition during relaxation. CLINICAL RELEVANCE: There is evidence for the presence of sensitization of the nociceptive system in subjects with occlusal disharmony. Possibly, deficient inhibition of extratrigeminal and trigeminal pain perception by relaxation might contribute to the development of TMD or other chronic pain disorders.

Anticipating agoraphobic situations: the neural correlates of panic disorder with agoraphobia.

BACKGROUND: Panic disorder with agoraphobia is characterized by panic attacks and anxiety in situations where escape might be difficult. However, neuroimaging studies specifically focusing on agoraphobia are rare. Here we used functional magnetic resonance imaging (fMRI) with disorder-specific stimuli to investigate the neural substrates of agoraphobia. METHOD: We compared the neural activations of 72 patients suffering from panic disorder with agoraphobia with 72 matched healthy control subjects in a 3-T fMRI study. To isolate agoraphobia-specific alterations we tested the effects of the anticipation and perception of an agoraphobia-specific stimulus set. During fMRI, 48 agoraphobia-specific and 48 neutral pictures were randomly presented with and without anticipatory stimulus indicating the content of the subsequent pictures (Westphal paradigm). RESULTS: During the anticipation of agoraphobia-specific pictures, stronger activations were found in the bilateral ventral striatum and left insula in patients compared with controls. There were no group differences during the perception phase of agoraphobia-specific pictures. CONCLUSIONS: This study revealed stronger region-specific activations in patients suffering from panic disorder with agoraphobia in anticipation of agoraphobia-specific stimuli. Patients seem to process these stimuli more intensively based on individual salience. Hyperactivation of the ventral striatum and insula when anticipating agoraphobia-specific situations might be a central neurofunctional correlate of agoraphobia. Knowledge about the neural correlates of anticipatory and perceptual processes regarding agoraphobic situations will help to optimize and evaluate treatments, such as exposure therapy, in patients with panic disorder and agoraphobia.

Neuropeptide S receptor gene -- converging evidence for a role in panic disorder.

Animal studies have suggested neuropeptide S (NPS) and its receptor (NPSR) to be involved in the pathogenesis of anxiety-related behavior. In this study, a multilevel approach was applied to further elucidate the role of NPS in the etiology of human anxiety. The functional NPSR A/T (Asn¹°7Ile) variant (rs324981) was investigated for association with (1) panic disorder with and without agoraphobia in two large, independent case-control studies, (2) dimensional anxiety traits, (3) autonomic arousal level during a behavioral avoidance test and (4) brain activation correlates of anxiety-related emotional processing in panic disorder. The more active NPSR rs324981 T allele was found to be associated with panic disorder in the female subgroup of patients in both samples as well as in a meta-analytic approach. The T risk allele was further related to elevated anxiety sensitivity, increased heart rate and higher symptom reports during a behavioral avoidance test as well as decreased activity in the dorsolateral prefrontal, lateral orbitofrontal and anterior cingulate cortex during processing of fearful faces in patients with panic disorder. The present results provide converging evidence for a female-dominant role of NPSR gene variation in panic disorder potentially through heightened autonomic arousal and distorted processing of anxiety-relevant emotional stimuli.

Sympathetic activity relates to adenosine A(2A) receptor gene variation in blood-injury phobia.

Variation in the candidate genes adenosine A(2A) receptor (A(2A)R), catechol-O-methyl-transferase (COMT), and norepinephrine transporter (NET) has been suggested to influence vulnerability to panic disorder. We therefore investigated patients with another anxiety disorder with an even higher heritability, the blood-injury phobia, for association of these variants and used sympathetic measures during venipuncture, which serve as a naturalistic trigger of anxiety and autonomic hyperarousal, as an intermediate phenotype of anxiety. Patients homozygous for the A(2A)R 1976T allele as compared to patients carrying at least one 1976C allele exhibited a significantly increased respiratory rate with a trend towards elevated measures of systolic and diastolic blood pressure and respiratory minute volume. None of the sympathetic measures were influenced by the COMT or NET polymorphisms.This study provides preliminary data suggesting an influence of the A(2A)R 1976C/T polymorphism on sympathetic psychophysiological indicators of anxiety-related arousal in blood-injury phobia and thereby further supports a role of the A(2A)R gene in the pathogenesis of anxiety disorders.

Mechanism of action in CBT (MAC): methods of a multi-center randomized controlled trial in 369 patients with panic disorder and agoraphobia.

Cognitive behavioral therapy (CBT) is efficacious for panic disorder with agoraphobia (PD/A). Nevertheless, the active ingredients of treatment and the mechanisms through which CBT achieves its effects remain largely unknown. The mechanisms of action in CBT (MAC) study was established to investigate these questions in 369 patients diagnosed with PD/A. The MAC study utilized a multi-center, randomized controlled design, with two active treatment conditions in which the administration of exposure was varied, and a wait-list control group. The special feature of MAC is the way in which imbedded experimental, psychophysiological, and neurobiological paradigms were included to elucidate therapeutic and psychopathological processes. This paper describes the aims and goals of the MAC study and the methods utilized to achieve them. All aspects of the research design (e.g., assessments, treatment, experimental procedures) were implemented so as to facilitate the detection of active therapeutic components, and the mediators and moderators of therapeutic change. To this end, clinical, behavioral, physiological, experimental, and genetic data were collected and will be integrated.

Validation of the German fear of pain questionnaire in a sample of children with mixed chronic pain conditions.

BACKGROUND: To date, no German instrument exists to measure pain-related fear in paediatric pain populations. The objective of the current study was to determine the construct validity of the translated German fear of pain questionnaire for children (GFOPQ-C) in a sample of children with mixed chronic pain disorders by testing the underlying factor structure, and its psychometric properties. METHOD: N = 241 children with mixed chronic pain disorders (aged 8-19 years) presenting to a specialized pain clinic completed the GFOPQ-C and several other pain, fear and disability measures. RESULTS: The two-factor structure of the FOPQ-C (fear, avoidance) was replicated. Internal consistency for the shortened German version was good for both subscales (Fear subscale: α = 0.89; avoidance subscale: α = 0.76). As expected, the fear subscale correlated highly with anxiety sensitivity (r = 0.63), pain catastrophizing (r = 0.62) and general anxiety (r = 0.54), while the avoidance subscale was more closely related to disability (r = 0.24) and school functioning (r = 0.28). Pain-related fear differed in children with chronic pain depending on their pain location with higher fear ratings in children with abdominal pain and musculoskeletal pain. CONCLUSION: The GFOPQ-C is a valid instrument that assesses two distinct dimensions of pain-related fear in children: fear and avoidance. Future research is needed to evaluate the impact of increased pain-related fear on outcomes over time as well as to examine pain-related fear among healthy children. This will enhance our knowledge of who might be particularly vulnerable to potentially dysfunctional trajectories, such as ongoing pain or anxiety symptoms. SIGNIFICANCE: The current study validates the first tool to assess pain-related fear in German-speaking children with chronic pain. Findings support two distinct domains: fear and activity avoidance.

N-acetylaspartate levels of left frontal cortex are associated with verbal intelligence in women but not in men: a proton magnetic resonance spectroscopy study.

The left frontal cortex plays an important role in executive function and complex language processing inclusive of spoken language. The purpose of this work was to assess metabolite levels in the left and right prefrontal cortex and left anterior cingulum by proton magnetic resonance spectroscopy and relate results to verbal intelligence (Wechsler Adult Intelligence Scale revised) in a sample of college-educated healthy volunteers (dorsolateral prefrontal cortex [DLPFC]: n=52, 23 females, and left anterior cingulum: n=62, 22 females; age range: 20-75 years). In women only, N-acetylaspartate in the DLPFC and in the left anterior cingulate cortex was positively correlated with vocabulary scores. Our data support the hypothesis of existing gender differences regarding the involvement of the left frontal cortex in verbal processing as reflected in different correlations of specific metabolites with verbal scores.

Blushing and physiological arousability in social phobia.

Blushing is the most prominent symptom of social phobia, and fear perception of visible anxiety symptoms is an important component of cognitive behavioral models of social phobia. However, it is not clear how physiological and psychological aspects of blushing and other somatic symptoms are linked in this disorder. The authors tested whether social situations trigger different facial blood volume changes (blushing) between social phobic persons with and without primary complaint of blushing and control participants. Thirty social phobic persons. 15 of whom were especially concerned about blushing, and 14 control participants were assessed while watching an embarrassing videotape, holding a conversation, and giving a talk. Only when watching the video did the social phobic persons blush more than controls blushed. Social phobic persons who complained of blushing did not blush more intensely than did social phobic persons without blushing complaints but had higher heart rates, possibly reflecting higher arousability of this subgroup.

Speech disturbances and gaze behavior during public speaking in subtypes of social phobia.

Twenty-four social phobics with public speaking anxiety and 25 nonphobic individuals (controls) gave a speech in front of two people. Subjective anxiety, gaze behavior, and speech disturbances were assessed. Based on subjects' fear ratings of social situations, phobics and controls were divided into the generalized and nongeneralized subtype. Results showed that generalized phobics reported the most, and nongeneralized controls the least anxiety during public speaking. All subjects had longer and more frequent eye contact when delivering a speech than when talking with an experimenter or sitting in front of an audience. Phobics showed more filled pauses, had longer silent pauses, paused more frequently, and spent more time pausing than controls when giving a speech. Generalized phobics spent more time pausing during their speech than the other subgroups (nongeneralized controls, generalized controls, and nongeneralized phobics). These results suggest that generalized phobics tended to shift attentional resources from speech production to other cognitive tasks.

Drinking motives in alcohol use disorder patients with and without social anxiety disorder.

The high comorbidity of alcohol use disorders (AUD) and social anxiety disorder (SAD) is often explained by excessive drinking in social situations to self-medicate social anxiety. Indeed, the motive to drink alcohol to lower social fears was found to be elevated in socially anxious persons. However, this social anxiety specific motive has not been directly investigated in primarily alcohol dependent individuals. We explored social anxiety, the motivation to drink alcohol in order to cope with social fears, and social anxiety as a consequence of drinking in AUD with and without comorbid SAD. Male AUD inpatients with (AUD+SAD group, N=23) and without comorbid SAD (N=37) completed a clinical interview and a questionnaire assessment. AUD+SAD patients reported higher levels of depression and an elevated motive to drink due to social anxiety but did not experience more social fears as a consequence of drinking. Previous results concerning alcohol drinking motives in order to relieve social fears could be replicated in a clinical AUD sample. Additionally, our findings suggest comorbid AUD+SAD patients to be more burdened regarding broader psychopathological symptoms. Thus, accessibility to SAD-specific screening and treatment procedures may be beneficial for primary AUD patients.

The functional -1019C/G HTR1A polymorphism and mechanisms of fear.

Serotonin receptor 1A gene (HTR1A) knockout mice show pronounced defensive behaviour and increased fear conditioning to ambiguous conditioned stimuli. Such behaviour is a hallmark of pathological human anxiety, as observed in panic disorder with agoraphobia (PD/AG). Thus, variations in HTR1A might contribute to neurophysiological differences within subgroups of PD/AG patients. Here, we tested this hypothesis by combining genetic with behavioural techniques and neuroimaging. In a clinical multicentre trial, patients with PD/AG received 12 sessions of manualized cognitive-behavioural therapy (CBT) and were genotyped for HTR1A rs6295. In four subsamples of this multicentre trial, exposure behaviour (n=185), defensive reactivity measured using a behavioural avoidance test (BAT; before CBT: n=245; after CBT: n=171) and functional magnetic resonance imaging (fMRI) data during fear conditioning were acquired before and after CBT (n=39). HTR1A risk genotype (GG) carriers more often escaped during the BAT before treatment. Exploratory fMRI results suggest increased activation of the amygdala in response to threat as well as safety cues before and after treatment in GG carriers. Furthermore, GG carriers demonstrated reduced effects of CBT on differential conditioning in regions including the bilateral insulae and the anterior cingulate cortex. Finally, risk genotype carriers demonstrated reduced self-initiated exposure behaviour to aversive situations. This study demonstrates the effect of HTR1A variation on defensive behaviour, amygdala activity, CBT-induced neural plasticity and normalization of defence behaviour in PD/AG. Our results, therefore, translate evidence from animal studies to humans and suggest a central role for HTR1A in differentiating subgroups of patients with anxiety disorders.

Slow recovery from voluntary hyperventilation in panic disorder.

OBJECTIVE: Because hyperventilation has figured prominently in theories of panic disorder (PD) but not of social phobia (SP), we compared predictions regarding diagnosis-specific differences in psychological and physiological measures before, during, and after voluntary hyperventilation. METHOD: Physiological responses were recorded in 14 patients with PD, 24 patients with SP, and 24 controls during six cycles of 1-minute of fast breathing alternating with 1 minute of recovery, followed by 3 minutes of fast breathing and 10 minutes of recovery. Speed of fast breathing was paced by a tone modulated at 18 cycles/minute, and depth by feedback aimed at achieving an end-tidal pCO2 of 20 mm Hg. These values were reached equally by all groups. RESULTS: During fast breathing, PD and SP patients reported more anxiety than controls, and their feelings of dyspnea and suffocation increased more from baseline. Skin conductance declined more slowly in PD over the six 1-minute fast breathing periods. At the end of the final 10-minute recovery, PD patients reported more awareness of breathing, dyspnea, and fear of being short of breath, and their pCO2s, heart rates, and skin conductance levels had returned less toward normal levels than in other groups. Their lower pCO2s were associated with a higher frequency of sigh breaths. CONCLUSIONS: PD and SP patients report more distress than controls to equal amounts of hypocapnia, but PD differ from SP patients and controls in having slower symptomatic and physiological recovery. This finding was not specifically predicted by hyperventilation, cognitive-behavioral, or suffocation alarm theories of PD.