The Neurobiology of Panic: A Chronic Stress Disorder

Neurochemical and genetic factors in panic disorder: a systematic review

This systematic review addresses the complex nature of Panic Disorder (PD), characterized by recurrent episodes of acute fear, with a focus on updating and consolidating knowledge regarding neurochemical, genetic, and epigenetic factors associated with PD. Utilizing the PRISMA methodology, 33 original peer-reviewed studies were identified, comprising 6 studies related to human neurochemicals, 10 related to human genetic or epigenetic alterations, and 17 animal studies. The review reveals patterns of altered expression in various biological systems, including neurotransmission, the Hypothalamic-Pituitary-Adrenal (HPA) axis, neuroplasticity, and genetic and epigenetic factors leading to neuroanatomical modifications. Noteworthy findings include lower receptor binding of GABAA and serotonin neurotransmitters in the amygdala. The involvement of orexin (ORX) neurons in the dorsomedial/perifornical region in triggering panic reactions is highlighted, with systemic ORX-1 receptor antagonists blocking panic responses. Elevated Interleukin 6 and leptin levels in PD patients suggest potential connections between stress-induced inflammatory changes and PD. Brain-derived neurotrophic factor (BDNF) and tyrosine receptor kinase B (TrkB) signaling are implicated in panic-like responses, particularly in the dorsal periaqueductal gray (dPAG), where BDNF's panicolytic-like effects operate through GABAA-dependent mechanisms. GABAergic neurons' inhibitory influence on dorsomedial and posterior hypothalamus nuclei is identified, potentially reducing the excitability of neurons involved in panic-like responses. The dorsomedial hypothalamus (DMH) is highlighted as a specific hypothalamic nucleus relevant to the genesis and maintenance of panic disorder. Altered brain lactate and glutamate concentrations, along with identified genetic polymorphisms linked to PD, further contribute to the intricate neurochemical landscape associated with the disorder. The review underscores the potential impact of neurochemical, genetic, and epigenetic factors on the development and expression of PD. The comprehensive insights provided by this systematic review contribute to advancing our understanding of the multifaceted nature of Panic Disorder and pave the way for targeted therapeutic strategies.

Electrocardiographic frontal QRS-T angle is independently associated with panic disorder

OBJECTIVE

Panic disorder (PD) may cause serious cardiac arrhythmias by causing electrical abnormalities. Abnormal P-wave axis (aPwa), presence of fragmented QRS (fQRS), wide frontal QRS-T angle (fQRSTa), QRS duration corrected (QRSdc) and log/ logQRS duration/RR interval (log/logQRS/RR) have been correlated with increased risk of serious supraventricular and ventricular cardiac arrhythmias in a general population. The purpose of this study was to compare these newly explored atrial and ventricular arrhythmia indicators in patients with PD and in healthy subjects.

METHOD

A total of 169 newly diagnosed PD patients and 128 healthy subjects were included in the study. The Panic and Agoraphobia Scale (PAS) was administered, and 12-lead electrocardiography (ECG) measurements were obtained. Electrocardiographic parameters including aPwa, fQRSTa, presence of fQRS, QRS duration corrected (QRSdc), and log/logQRS duration/RR distance (log/logQRS/RR) were compared between the two groups.

RESULTS

aPwa and fQRS, in addition to fQRSTa, QRSdc, and log/ logQRS/RR ratio values, were significantly increased in the PD group compared to healthy controls. Correlation analyses revealed that wider fQRSTa, number of fQRS derivation, number of total fQRS, wider QRSdc, and log/logQRS/RR ratio significantly correlated with PAS score. Logistic regression analysis demonstrated that fQRSTa and the number of total fQRS were independently associated with PD.

CONCLUSION

PD is associated with wider fQRSTa, QRSdc, and log/logQRS/RR in addition to the increased abnormal aPwa and presence of fQRS. These findings suggest that untreated PD patients may be susceptible to supraventricular and ventricular arrhythmia, indicating that ECG should be routinely obtained in the management of PD patients.

A three-dimensional model of neural activity and phenomenal-behavioral patterns

How phenomenal experience and behavior are related to neural activity in physiology and psychopathology represents a fundamental question in neuroscience and psychiatry. The phenomenal-behavior patterns may be deconstructed into basic dimensions, i.e., psychomotricity, affectivity, and thought, which might have distinct neural correlates. This work provides a data overview on the relationship of these phenomenal-behavioral dimensions with brain activity across physiological and pathological conditions (including major depressive disorder, bipolar disorder, schizophrenia, attention-deficit/hyperactivity disorder, anxiety disorders, addictive disorders, Parkinson's disease, Tourette syndrome, Alzheimer's disease, and frontotemporal dementia). Accordingly, we propose a three-dimensional model of neural activity and phenomenal-behavioral patterns. In this model, neural activity is organized into distinct units in accordance with connectivity patterns and related input/output processing, manifesting in the different phenomenal-behavioral dimensions. (1) An external neural unit, which involves the sensorimotor circuit/brain's sensorimotor network and is connected with the external environment, processes external inputs/outputs, manifesting in the psychomotor dimension (processing of exteroception/somatomotor activity). External unit hyperactivity manifests in psychomotor excitation (hyperactivity/hyperkinesia/catatonia), while external unit hypoactivity manifests in psychomotor inhibition (retardation/hypokinesia/catatonia). (2) An internal neural unit, which involves the interoceptive-autonomic circuit/brain's salience network and is connected with the internal/body environment, processes internal inputs/outputs, manifesting in the affective dimension (processing of interoception/autonomic activity). Internal unit hyperactivity manifests in affective excitation (anxiety/dysphoria-euphoria/panic), while internal unit hypoactivity manifests in affective inhibition (anhedonia/apathy/depersonalization). (3) An associative neural unit, which involves the brain's associative areas/default-mode network and is connected with the external/internal units (but not with the environment), processes associative inputs/outputs, manifesting in the thought dimension (processing of ideas). Associative unit hyperactivity manifests in thought excitation (mind-wandering/repetitive thinking/psychosis), while associative unit hypoactivity manifests in thought inhibition (inattention/cognitive deficit/consciousness loss). Finally, these neural units interplay and dynamically combine into various neural states, resulting in the complex phenomenal experience and behavior across physiology and neuropsychiatric disorders.

Connecting chronic stress and anxiety: a multi-dimensional perspective

Studies show a connection between anxiety and stress, but with little differentiation between different domains of stress. In this article, we utilize a multi-dimensional approach to better understand the relationship between different chronic stress domains and anxiety. This will allow researchers to identify and address those areas of stress that are most relevant with regard to anxiety. We used data from a sub sample of the LIFE-Adult-Study (n = 1085) to analyze the association between nine different areas of chronic stress (Trier Inventory for Chronic Stress, TICS) and anxiety (General Anxiety Disorder 7, GAD-7), controlling for sociodemographic variables, personality, and social support. There was a significant and positive association between Work Overload, Pressure to Perform, Social Tensions, Social Isolation, Chronic Worrying, and anxiety. After including the control variables, only Work Overload and Chronic Worrying remained significant. By focusing on Work Overload and Chronic Worrying researchers, practitioners, and policy makers can help to mitigate anxiety and related health problems in the population in an efficient way.

Serum BDNF levels and state anxiety are associated with somatic symptoms in patients with panic disorder

Background

We aimed to explore the predictive role of serum BDNF and anxiety-related variables in changes in somatic symptoms post-escitalopram treatment in panic disorder (PD) patients.

Methods

Ninety PD patients and 99 healthy controls (HCs) were enrolled. PD patients received an 8-week escitalopram treatment. All patients were administered the Panic Disorder Severity Scale-Chinese Version (PDSS-CV) and State-Trait Anxiety Inventory (STAI) to assess panic and anxiety-related symptoms, respectively. Patient Health Questionnaire 15-item scale (PHQ-15) was performed to measure somatic symptoms, and the blood sample was collected to detect serum BDNF levels in all participants. We performed partial correlation analysis and multiple linear regression to explore correlates of PHQ-15 and predictors of PHQ-15 changes post-escitalopram treatment after controlling for age, gender, education levels (set as a dummy variable), the current duration, comorbid AP, and/or GAD.

Results

Compared to HCs, PD patients had lower serum BDNF levels and higher PHQ-15 scores that could be improved post-escitalopram treatment. Lower baseline STAI state (b = -0.07, p = 0.004), and PDSS-CV scores (b = -0.25, p = 0.007), but higher baseline serum BDNF levels (b = 0.35, p = 0.007) contributed to the prediction of PHQ-15 changes post-escitalopram treatment.

Conclusion

State anxiety, serum BDNF levels, and panic severity could predict changes in somatic symptoms post-escitalopram treatment, our results highlighted that serum BDNF could serve as a biological indicator for improving somatic symptoms in PD patients.

Treatment of Comorbid Anxiety and Epilepsy

Objective: Anxiety is among the most common psychiatric illnesses, and it commonly co-occurs with epilepsy. This review of the existing literature on anxiety comorbid with epilepsy aims to generate new insights into strategies for assessment and treatment. Methods: The authors conducted a narrative literature review to select key publications that help clarify the phenomenology and management of comorbid anxiety and epilepsy. Results: Anxiety symptoms may be relevant even if the criteria for a diagnosis of an anxiety disorder are not met. Associating specific seizure types or seizure localization with anxiety symptoms remains difficult; however, the amygdala is a brain region commonly associated with seizure foci and panic or fear sensations. The hypothalamic-pituitary-adrenal axis may also be relevant for anxiety symptoms, particularly for the selection of treatments. Nonpharmacological treatment is appropriate for anxiety comorbid with epilepsy, particularly because relaxation techniques may reduce hypersympathetic states, which improve symptoms. Medication options include antidepressants and anticonvulsants that may have efficacy for anxiety symptoms. Benzodiazepines are a good choice to address this comorbid condition, although side effects may limit utility. Conclusions: Ultimately, there are numerous treatment options, and although there is a limited evidence base, quality of life may be improved with appropriate treatment for individuals experiencing comorbid anxiety and epilepsy.

Transcranial direct current stimulation does not improve clinical and neurophysiological outcomes in panic disorder: A randomized sham-controlled trial

AIM

Emerging evidence suggests that transcranial direct current stimulation (tDCS) has anxiolytic effects and may enhance emotional processing of threat and reduce threat-related attentional bias. Panic disorder (PD) is considered to be a fear network disorder along with prefrontal activity alterations. We aim to assess the effect of tDCS on clinical and physiological parameters in PD for the first time.

METHODS

In this triple-blind randomized sham-controlled pilot study, 30 individuals with PD were allocated into active and sham groups to receive 10 sessions of tDCS targeting the dorsolateral prefrontal cortex bilaterally at 2 mA for 20-min duration over 2 weeks. The clinical severity, threat-related attentional bias, interoceptive accuracy, and emotional recognition were assessed before, immediately after, and 1 month after tDCS.

RESULTS

Active tDCS, in comparison to sham, did not elicit more favorable clinical and neuropsychological/physiological outcomes in PD.

CONCLUSION

The present study provides the first clinical and neurobehavioral results of prefrontal tDCS in PD and indicates that prefrontal tDCS was not superior to sham in PD.

Valproate Adjuvant Cognitive Behavioral Therapy in Panic Disorder Patients With Comorbid Bipolar Disorder: Case Series and Review of the Literature

Anxiety disorders are the most common comorbid psychiatric disorders in patients with bipolar disorder. Managing anxiety symptoms in comorbid conditions is challenging and has received little research interest. The findings from preclinical research on fear conditioning, an animal model of anxiety disorder, have suggested that memory reconsolidation updating (exposure-based therapy) combined with valproate might facilitate the amelioration of fear memories. Here, three cases of successful amelioration of agoraphobia and panic symptoms through valproate adjuvant therapy for cognitive behavioral therapy in patients who failed to respond to two to three consecutive standard pharmacotherapy trials over several years are described. To the best of the author's knowledge, this is the first attempt to combine CBT with valproate in patients with panic disorder, agoraphobia, and comorbid bipolar disorder. Additionally, the background preclinical research on this combination therapy based on the reconsolidation-updating mechanism, the inhibition of histone deacetylase 2, and critical period reopening, off-label use of valproate in panic disorder, plasticity-augmented psychotherapy, and how to combine valproate with CBT is discussed.

ENIGMA-anxiety working group: Rationale for and organization of large-scale neuroimaging studies of anxiety disorders

Anxiety disorders are highly prevalent and disabling but seem particularly tractable to investigation with translational neuroscience methodologies. Neuroimaging has informed our understanding of the neurobiology of anxiety disorders, but research has been limited by small sample sizes and low statistical power, as well as heterogenous imaging methodology. The ENIGMA-Anxiety Working Group has brought together researchers from around the world, in a harmonized and coordinated effort to address these challenges and generate more robust and reproducible findings. This paper elaborates on the concepts and methods informing the work of the working group to date, and describes the initial approach of the four subgroups studying generalized anxiety disorder, panic disorder, social anxiety disorder, and specific phobia. At present, the ENIGMA-Anxiety database contains information about more than 100 unique samples, from 16 countries and 59 institutes. Future directions include examining additional imaging modalities, integrating imaging and genetic data, and collaborating with other ENIGMA working groups. The ENIGMA consortium creates synergy at the intersection of global mental health and clinical neuroscience, and the ENIGMA-Anxiety Working Group extends the promise of this approach to neuroimaging research on anxiety disorders.

Stress in obstructive sleep apnea

People with obstructive sleep apnea (OSA) often have psychological symptoms including depression and anxiety, which are commonly treated with anti-depression or anti-anxiety interventions. Psychological stress is a related symptom with different intervention targets that may also improve mental state, but this symptom is not well characterized in OSA. We therefore aimed to describe stress in relation to other psychological symptoms. We performed a prospective cross-sectional study of 103 people, 44 untreated OSA (mean ± s.d. age: 51.2 ± 13.9 years, female/male 13/31) and 57 healthy control participants (age: 46.3 ± 13.8 years, female/male 34/23). We measured stress (Perceived Stress Scale; PSS), excessive daytime sleepiness (Epworth Sleepiness Scale; ESS), depressive symptoms (Patient Health Questionnaire; PHQ-9), and anxiety symptoms (General Anxiety Disorder; GAD-7). We compared group means with independent samples t-tests and calculated correlations between variables. Mean symptom levels were higher in OSA than control, including PSS (mean ± s.d.: OSA = 15.3 ± 6.9, control = 11.4 ± 5.5; P = 0.002), GAD-7 (OSA = 4.8 ± 5.0, control = 2.1 ± 3.9; P = 0.02), PHQ-9 (OSA = 6.9 ± 6.1, control = 2.6 ± 3.8; P = 0.003) and ESS (OSA = 8.1 ± 5.3, control = 5.0 ± 3.3; P = 0.03). Similar OSA-vs-control differences appeared in males, but females only showed significant differences in PHQ-9 and ESS, not PSS or GAD-7. PSS correlated strongly with GAD-7 and PHQ-9 across groups (R = 0.62–0.89), and moderately with ESS. Perceived stress is high in OSA, and closely related to anxiety and depressive symptoms. The findings support testing stress reduction in OSA.

Behavioral and brain mechanisms mediating conditioned flight behavior in rats

Environmental contexts can inform animals of potential threats, though it is currently unknown how context biases the selection of defensive behavior. Here we investigated context-dependent flight responses with a Pavlovian serial-compound stimulus (SCS) paradigm that evokes freeze-to-flight transitions. Similar to previous work in mice, we show that male and female rats display context-dependent flight-like behavior in the SCS paradigm. Flight behavior was dependent on contextual fear insofar as it was only evoked in a shock-associated context and was reduced in the conditioning context after context extinction. Flight behavior was only expressed to white noise regardless of temporal order within the compound. Nonetheless, rats that received unpaired SCS trials did not show flight-like behavior to the SCS, indicating it is associative. Finally, we show that pharmacological inactivation of two brain regions critical to the expression of contextual fear, the central nucleus of the amygdala (CeA) and bed nucleus of the stria terminalis (BNST), attenuates both contextual fear and flight responses. All of these effects were similar in male and female rats. This work demonstrates that contextual fear can summate with cued and innate fear to drive a high fear state and transition from post-encounter to circa-strike defensive modes.

Facial emotion perception in young female students with subsyndromal panic disorder. Behavioral and ERP study

This study aimed to examine the behavioral and neural correlates of facial emotion recognition in young women with subsyndromal panic disorder (SPD). In the experiment 15 non-medicated women with SPD and 17 matched healthy controls were tasked with recognizing angry, fearful, happy, and neutral facial expressions, and accuracy, reaction time (RT), and event-related potentials (ERPs) were recorded. Significant between-group differences in behavioral characteristics (accuracy of emotion recognition and RT) were not found, however, the SPD subjects demonstrated a slower response to fearful expressions compared to neutral and happy expressions. More distinct between-group differences were observed for the EPRs. The SPD subjects demonstrated increased amplitudes of the P100 ERP component in the occipital area and the P200 component over the occipital and temporal regions. In the frontal regions the SPD group showed a greater amplitude of the N200 component and also an increased negativity 350-450 ms after stimulus presentation. According to the dipole source modeling data, the SPD subjects showed enhanced activation in the extra-striate cortex which increased in intensity when angry and fearful faces were presented. Thus, young women with SPD which manifested in infrequent panic attacks showed significant alterations in ERP characteristics of emotional processing, which may be considered as a more sensitive indicator of early-stage panic disorder than the observed behavioral measures.

Higher Rightward Laterality of the Hippocampal Tail and Its Association with Early Trauma in Panic Disorder

OBJECTIVE

Early trauma (ET) is widely recognized as a contributing factor to the development of panic disorder (PD) in patients. However, there is a dearth of research on the specific volumes of hippocampal subregions and their laterality with respect to ET and PD.

METHODS

A total of 30 subjects with PD and 30 age- and sex-matched healthy controls (HCs) were included in this study. All the subjects were evaluated by 3T-magnetic resonance imaging. FreeSurfer version 6.0 was used for volumetric analysis of the hippocampal subregions and their laterality. A shortened version of the Early Trauma Inventory Self Report (ETISR) as well as Anxiety Sensitivity Inventory-Revised (ASI-R), and Panic Disorder Severity Scale were utilized for analysis.

RESULTS

Multivariate analysis of variance showed that the volume of the right hippocampal tail and laterality indices (LIs) of the hippocampal body and tail were significantly larger in subjects with PD relative to HCs. The significance of the observations remained unchanged after multivariate analysis of covariance, controlling for age, sex, years of education, medication, depressive symptoms, and intracranial volume as covariates. The LIs of the hippocampal tails that showed a significant correlation to ETISR emotional and physical subscales were also associated with ASI-R for cardiovascular symptoms in PD.

CONCLUSION

Our study displayed an increased rightward lateralization of the hippocampal tails in subjects with PD compared with HCs. This alteration in the brain, which was associated with early emotional and physical trauma, would negatively affect anxiety sensitivity to cardiovascular symptoms in subjects with PD.

Ketamine and rapid acting antidepressants: Are we ready to cure, rather than treat depression?

Depression is a leading cause of disability, with often chronic course of illness and high treatment resistance in a large proportion of patients. In the current short perspective paper, we present evidence supporting the presence of synaptic-based chronic stress pathology (CSP) in depression and across a number of psychiatric disorders. We summarize the synaptic connectivity model of CSP, and briefly review related preclinical and clinical evidence, while providing appropriate references for more comprehensive reviews and alternative models. We then underscore some gaps in the literature and provide various tips for future directions.

The Neurobiology and Pharmacotherapy of Posttraumatic Stress Disorder

New approaches to the neurobiology of posttraumatic stress disorder (PTSD) are needed to address the reported crisis in PTSD drug development. These new approaches may require the field to move beyond a narrow fear-based perspective, as fear-based medications have not yet demonstrated compelling efficacy. Antidepressants, particularly recent rapid-acting antidepressants, exert complex effects on brain function and structure that build on novel aspects of the biology of PTSD, including a role for stress-related synaptic dysconnectivity in the neurobiology and treatment of PTSD. Here, we integrate this perspective within a broader framework-in other words, a dual pathology model of ( a) stress-related synaptic loss arising from amino acid-based pathology and ( b) stress-related synaptic gain related to monoamine-based pathology. Then, we summarize the standard and experimental (e.g., ketamine) pharmacotherapeutic options for PTSD and discuss their putative mechanism of action and clinical efficacy.

The neurobiology of depression, ketamine and rapid-acting antidepressants: Is it glutamate inhibition or activation?

The discovery of the antidepressant effects of ketamine has opened a breakthrough opportunity to develop a truly novel class of safe, effective, and rapid-acting antidepressants (RAADs). In addition, the rapid and robust biological and behavioral effects of ketamine offered a unique opportunity to utilize the drug as a tool to thoroughly investigate the neurobiology of stress and depression in animals, and to develop sensitive and reproducible biomarkers in humans. The ketamine literature over the past two decades has considerably enriched our understanding of the mechanisms underlying chronic stress, depression, and RAADs. However, considering the complexity of the pharmacokinetics and in vivo pharmacodynamics of ketamine, several questions remain unanswered and, at times, even answered questions continue to be considered controversial or at least not fully understood. The current perspective paper summarizes our understanding of the neurobiology of depression, and the mechanisms of action of ketamine and other RAADs. The review focuses on the role of glutamate neurotransmission - reviewing the history of the "glutamate inhibition" and "glutamate activation" hypotheses, proposing a synaptic connectivity model of chronic stress pathology, and describing the mechanism of action of ketamine. It will also summarize the clinical efficacy findings of putative RAADs, present relevant human biomarker findings, and discuss current challenges and future directions.