Cortical morphometric predictors of autonomic dysfunction in generalized anxiety disorder

Causal associations between hypertension and abnormal brain cortical structures: Insights from a bidirectional Mendelian randomization study

Background

Observational studies suggest that hypertension affects brain cortical structure. However, the potential causal association has yet to be entirely determined. Thus, we aim to assess the causality between hypertension and abnormal cortical structure.

Methods

We conducted a bidirectional Mendelian randomization (MR) study to estimate their relationship. Genome-wide association study summary statistics of hypertension (n = 484,598) and brain cortical (surface area and thickness) (n = 51,665) were derived from publicly available databases. Sensitivity analyses were applied to ensure the robustness of the results.

Results

The study showed that hypertension was associated with a decline in total brain cortical thickness [β, -0.0308 mm; 95 % confidence interval (CI), -0.0610 to -0.0007; p = 0.045] and the insula thickness [β, -0.0415 mm; 95 % CI, -0.0772 to -0.0057; p = 0.023]. A null association was observed between hypertension and other brain regions. In the reverse MR analysis, the total cortical surface area (per 1 SD increase) significantly decreased the incidence of hypertension [odds ratio (OR), 0.976; 95 % CI, 0.963 to 0.990; p = 5.15E-04]. The caudal anterior cingulate cortex thickness (per 1 SD increase) was significantly associated with an increased risk of hypertension [OR, 1.057; 95 % CI, 1.034 to 1.082; p = 1.08E-06]. Moreover, we found several nominally associated gyri, including cuneus, isthmus cingulate, middle temporal, para hippocampal, posterior cingulate, superior temporal, and medial orbitofrontal, influence the incidence of hypertension.

Conclusion

Our study showed causal relationships between hypertension and changes in specific brain cortical, providing new evidence for the heart-brain axis theory.

Grey matter alterations in generalized anxiety disorder: A voxel-wise meta-analysis of voxel-based morphometry studies

OBJECTIVE

Grey matter, a crucial component of the brain, has been found altered in generalized anxiety disorder (GAD) of several voxel-based morphometry studies. The conclusive and consistent grey matter alterations in GAD have not been confirmed.

METHOD

Eleven voxel-based morphometry studies of GAD patients were included in the current systematic review and meta-analysis. The linear model of anxiety severity scores was applied to explore the relationship of grey matter alterations and anxiety severity. The subgroup analysis of adult GAD and adolescent GAD was also performed.

RESULTS

Significantly modest grey matter alterations in the left superior temporal gyrus of patients with GAD were found. The anxiety severity score was significantly correlated with grey matter alterations in the right insula, lenticular nucleus, putamen and striatum. The subgroup analysis of adult GAD and adolescent GAD all failed to show significant grey matter alterations. However, in the adult GAD subgroup, anxiety severity score was significantly correlated with grey matter alterations in the right insula.

CONCLUSION

GAD might have the modest grey matter alterations in the left superior temporal gyrus. Anxiety severity might be related to the grey matter alterations in the limbic regions, such as the right insula, lenticular nucleus, putamen and striatum. This kind of correlation might be related to the effects of adult GAD. Future studies with adequate sample sizes and sophisticated GAD categories will be needed.

Heart Rate Variability in Psychiatric Disorders: A Systematic Review

Introduction

Heart rate variability (HRV) is a measure of the fluctuation in time interval between consecutive heart beats. Decreased heart rate variability has been shown to have associations with autonomic dysfunction in psychiatric conditions such as depression, substance abuse, anxiety, and schizophrenia, although its use as a prognostic tool remains highly debated. This study aims to review the current literature on heart rate variability as a diagnostic and prognostic tool in psychiatric populations.

Methods

A literature search was conducted using the MEDLINE, EMBASE, Cochrane, and PsycINFO libraries to identify full-text studies involving adult psychiatric populations that reported HRV measurements. From 1647 originally identified, 31 studies were narrowed down through an abstract and full-text screen. Studies were excluded if they enrolled adolescents or children, used animal models, enrolled patients with another primary diagnosis other than psychiatric as outlined by the diagnostic and statistical manual of mental disorders (DSM) V, or if they assessed HRV in the context of treatment rather than diagnosis. Study quality assessment was conducted using a modified Downs and Blacks quality assessment tool for observational rather than interventional studies. Data were reported in four tables: 1) summarizing study characteristics, 2) methods of HRV detection, 3) key findings and statistics, and 4) quality assessment.

Results

There is significant variability between studies in their methodology of recording as well as reporting HRV, which makes it difficult to meaningfully interpret data that is clinically applicable due to the presence of significant bias in existing studies. The presence of an association between HRV and the severity of various psychiatric disorders, however, remains promising.

Conclusion

Future studies should be done to further explore how HRV parameters may be used to enhance the diagnosis and prognosis of several psychiatric disorders.

Topographical similarity of cortical thickness represents generalized anxiety symptoms in adolescence

Generalized anxiety disorder (GAD) is a common condition characterized by excessive and uncontrollable worry, along with its high comorbidity rates. Despite increasing efforts to identify the neural underpinnings of GAD, neuroimaging research using cortical thickness have yielded largely inconsistent results. To address this, we adopted an inter-subject representational similarity analysis framework to explore a potential nonlinear relationship between vertex-wise cortical thickness and generalized anxiety symptom severity. We utilized a sample of 120 adolescents (13-18 years of age) from the Healthy Brain Network dataset. Here, we found greater topographical resemblance among participants with heightened generalized anxiety symptoms in the left caudal anterior cingulate and pericalcarine cortex. These results were not driven by the effects of age, sex, ADHD diagnosis, and GAD diagnosis. Such associations were not observed when including a group of younger participants (11-12 years of age) for analyses, highlighting the importance of age range selection when considering the link between cortical thickness and anxiety. Our findings reveal a novel cortical thickness topography that represents generalized anxiety in adolescents, which is embedded within the shared geometries between generalized anxiety symptoms and cortical thickness.

Dimensional distress and orbitofrontal thickness in anxiety patients

Thickness of the medial orbitofrontal cortex (mOFC) was assessed as it varied with reported symptoms of anxiety and depression in a large sample of anxiety patients. A principal component analysis identified a primary factor of transdiagnostic dimensional distress that predicted 24% of the mOFC variance. Severity of distress symptomology was associated with thinning of the mOFC in both hemispheres for both men and women, regardless of the primary DSM diagnosis. Taken together, the data indicate that mOFC thickness might be useful as an objective measure of disorder severity as well as to assess pharmacological or psychological treatment outcome.

Cortical mean diffusivity is reliable in measuring brain abnormalities in drug-naïve essential tremor patients

OBJECTIVE

Essential tremor (ET) is a common movement disorder, but the pathogenesis is poorly understood. Several associated brain areas were reported with inconsistent results due to heterogeneous populations. It is necessary to analyze a more homogeneous patient group.

METHODS

We recruited 25 drug-naïve ET patients and 36 age- and sex-matched controls. All participants were right-handed. ET. ET was defined according to diagnostic criteria of the Consensus Statement of the Movement Disorder Society on Tremor. ET patients were divided into sporadic (SET) and familial ET (FET). We assessed tremor severity in ET. The cortical microstructural changes were compared between ET patients and controls using mean diffusivity (MD) of diffusion tensor imaging, and cortical thickness. The correlation of tremor severity with the cortical MD and thickness were respectively analyzed.

RESULTS

MD values were increased in the insular, precuneus, medial orbitofrontal, posterior, and isthmus cingulate and temporo-occipital areas in ET. In comparison between SET and FET, MD values were higher in the superior and caudal middle frontal, postcentral, and temporo-occipital regions in FET. The cortical thickness of ET patients was more increased in the left lingual gyrus and lower in the right bankssts gyrus. We could not find any correlation of tremor severity with the MD values in ET patients. Still, there was a positive correlation with the cortical thickness of the frontal and parietal areas.

CONCLUSIONS

Our results support the idea that ET is a disorder that disrupts widespread brain regions and indicates that cortical MD may be more sensitive to measure brain abnormalities than cortical thickness.

Brain morphometry points to emerging patterns of psychosis, depression, and anxiety vulnerability over a 2-year period in childhood

BACKGROUND

Gray matter morphometry studies have lent seminal insights into the etiology of mental illness. Existing research has primarily focused on adults and then, typically on a single disorder. Examining brain characteristics in late childhood, when the brain is preparing to undergo significant adolescent reorganization and various forms of serious psychopathology are just first emerging, may allow for a unique and highly important perspective of overlapping and unique pathogenesis.

METHODS

A total of 8645 youth were recruited as part of the Adolescent Brain and Cognitive Development study. Magnetic resonance imaging scans were collected, and psychotic-like experiences (PLEs), depressive, and anxiety symptoms were assessed three times over a 2-year period. Cortical thickness, surface area, and subcortical volume were used to predict baseline symptomatology and symptom progression over time.

RESULTS

Some features could possibly signal common vulnerability, predicting progression across forms of psychopathology (e.g. superior frontal and middle temporal regions). However, there was a specific predictive value for emerging PLEs (lateral occipital and precentral thickness), anxiety (parietal thickness/area and cingulate), and depression (e.g. parahippocampal and inferior temporal).

CONCLUSION

Findings indicate common and distinct patterns of vulnerability for varying forms of psychopathology are present during late childhood, before the adolescent reorganization, and have direct relevance for informing novel conceptual models along with early prevention and intervention efforts.

Higher polygenic risk scores for anxiety disorders are associated with reduced area in the anterior cingulate gyrus

Anxiety disorders are heterogeneous, show a moderate genetic contribution and are associated with inconsistent cortical structure alterations. Here, we investigated whether genetic factors for anxiety disorders contribute to cortical alterations by conducting polygenic risk score (PRS) analyses. We calculated PRSs for anxiety disorders at several P value thresholds (from P_T ≤ 5.0 × 10^-8 to P_T ≤ 1.0) based on the latest large-scale genome-wide association study of anxiety disorders from the UK biobank (25,453 cases; 58,113 controls) in an independent sample of psychiatrically and physically healthy subjects (n = 174). Using regression after adjusting for confounding factors, we tested whether these PRSs were associated with the surface area and cortical thickness in 34 bilateral brain regions extracted using FreeSurfer. A higher PRS for anxiety disorders at P_T ≤ 1.0 was significantly associated with a reduced right caudal anterior cingulate area (beta = -0.25, p_uncorrected = 9.51 × 10^-4, p_corrected = 0.032). PRSs based on more common SNPs, especially from P_T ≤ 0.01 to P_T ≤ 1.0, were associated with the right caudal anterior cingulate area (a maximum at P_T ≤ 0.5: R² = 0.066, beta = -0.27, p_uncorr = 3.81 × 10^-4, p_corr = 0.013). Furthermore, individuals in the highest quartile for anxiety disorder PRS had lower surface area and volume in the right anterior cingulate gyrus than those in the lowest quartile. We suggest a shared genetic etiology between anxiety disorders and structural features of the anterior cingulate gyrus, possibly contributing to the pathogenesis of anxiety disorders via emotional dysregulations. Our findings suggest the potential usefulness of PRS to reduce pathological heterogeneity among anxiety disorders.

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex for Treatment of Neuropsychiatric Disorders

Background

The dorsolateral prefrontal cortex (DLPFC) is a key node of the frontal cognitive circuit. It is involved in executive control and many cognitive processes. Abnormal activities of DLPFC are likely associated with many psychiatric diseases. Modulation of DLPFC may have potential beneficial effects in many neural and psychiatric diseases. One of the widely used non-invasive neuromodulation technique is called transcranial direct current stimulation (or tDCS), which is a portable and affordable brain stimulation approach that uses direct electrical currents to modulate brain functions.

Objective

This review aims to discuss the results from the past two decades which have shown that tDCS can relieve clinical symptoms in various neurological and psychiatric diseases.

Methods

Here, we performed searches on PubMed to collect clinical and preclinical studies that using tDCS as neuromodulation technique, DLPFC as the stimulation target in treating neuropsychiatric disorders. We summarized the stimulation sites, stimulation parameters, and the overall effects in these studies.

Results

Overall, tDCS stimulation of DLPFC could alleviate the clinical symptoms of schizophrenia, depression, drug addiction, attention deficit hyperactivity disorder and other mental disorders.

Conclusion

The stimulation parameters used in these studies were different from each other. The lasting effect of stimulation was also not consistent. Nevertheless, DLPFC is a promising target for non-invasive stimulation in many psychiatric disorders. TDCS is a safe and affordable neuromodulation approach that has potential clinical uses. Larger clinical studies will be needed to determine the optimal stimulation parameters in each condition.

Association of Generalized Anxiety Disorder With Autonomic Hypersensitivity and Blunted Ventromedial Prefrontal Cortex Activity During Peripheral Adrenergic Stimulation: A Randomized Clinical Trial

IMPORTANCE

β-Adrenergic stimulation elicits heart palpitations and dyspnea, key features of acute anxiety and sympathetic arousal, yet no neuroimaging studies have examined how the pharmacologic modulation of interoceptive signals is associated with fear-related neurocircuitry in individuals with generalized anxiety disorder (GAD).

OBJECTIVE

To examine the neural circuitry underlying autonomic arousal induced via isoproterenol, a rapidly acting, peripheral β-adrenergic agonist akin to adrenaline.

DESIGN, SETTING, AND PARTICIPANTS

This crossover randomized clinical trial of 58 women with artifact-free data was conducted from January 1, 2017, to November 31, 2019, at the Laureate Institute for Brain Research in Tulsa, Oklahoma.

EXPOSURES

Functional magnetic resonance imaging was used to assess neural responses during randomized intravenous bolus infusions of isoproterenol (0.5 and 2.0 μg) and saline, each administered twice in a double-blind fashion.

MAIN OUTCOMES AND MEASURES

Blood oxygen level-dependent responses across the whole brain during isoproterenol administration in patients with GAD vs healthy comparators. Cardiac and respiratory responses, as well as interoceptive awareness and anxiety, were also measured during the infusion protocol.

RESULTS

Of the 58 female study participants, 29 had GAD (mean [SD] age, 26.9 [6.8] years) and 29 were matched healthy comparators (mean [SD] age, 24.4 [5.0] years). During the 0.5-μg dose of isoproterenol, the GAD group exhibited higher heart rate responses (b = 5.34; 95% CI, 2.06-8.61; P = .002), higher intensity ratings of cardiorespiratory sensations (b = 8.38; 95% CI, 2.05-14.71; P = .01), higher levels of self-reported anxiety (b = 1.04; 95% CI, 0.33-1.76; P = .005), and significant hypoactivation in the ventromedial prefrontal cortex (vmPFC) that was evident throughout peak response (Cohen d = 1.55; P < .001) and early recovery (Cohen d = 1.52; P < .001) periods. Correlational analysis of physiological and subjective indexes and percentage of signal change extracted during the 0.5-μg dose revealed that vmPFC hypoactivation was inversely correlated with heart rate (r56 = -0.51, adjusted P = .001) and retrospective intensity of both heartbeat (r56 = -0.50, adjusted P = .002) and breathing (r56 = -0.44, adjusted P = .01) sensations. Ventromedial prefrontal cortex hypoactivation correlated inversely with continuous dial ratings at a trend level (r56 = -0.38, adjusted P = .051), whereas anxiety (r56 = -0.28, adjusted P = .27) and chronotropic dose 25 (r56 = -0.14, adjusted P = .72) showed no such association.

CONCLUSIONS AND RELEVANCE

In this crossover randomized clinical trial, women with GAD exhibited autonomic hypersensitivity during low levels of adrenergic stimulation characterized by elevated heart rate, heightened interoceptive awareness, increased anxiety, and a blunted neural response localized to the vmPFC. These findings support the notion that autonomic hyperarousal may be associated with regulatory dysfunctions in the vmPFC, which could serve as a treatment target to help patients with GAD more appropriately appraise and regulate signals of sympathetic arousal.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02615119.

Transcranial Electrical Stimulation for Relief of Peripartum Mental Health Disorders in Women Undergoing Cesarean Section With Combined Spinal-Epidural Anesthesia: A Pilot Randomized Clinical Trial

OBJECTIVE

This study aimed to explore transcranial electrical stimulation (tES) to relieve peripartum anxiety and depressive symptoms in women undergoing cesarean section with combined spinal-epidural anesthesia.

METHODS

This double-blind, randomized, sham-controlled trial was conducted in the Affiliated Hospital of Xuzhou Medical University from March 2021 and May 2021. One hundred and forty-eight full-term parturients giving birth by elective cesarean section were selected, and 126 were included in the intent-to-treat analysis. Parturients were provided standardized anesthesia and randomized to the active-tES (a-tES) group and sham-tES group. Parturients and outcome assessors were blinded to treatment allocation. The primary outcome was the changes in peripartum mental health disorders, including anxiety, assessed by the Pregnancy-Related Anxiety Questionnaire-Revised 2 (PRAQ-R2). Secondary outcomes included peripartum depressive symptoms, assessed by the Edinburgh Postnatal Depression Scale (EPDS), maternal satisfaction, fatigue level, sleep quality index, and pain score during and after operation. Data were collected before entering the operating room (T0), between post-anesthesia and pre-surgery (T1), before leaving the operating room (T2), and at 24 h post-surgery (T3).

RESULTS

One hundred and twenty-six eligible parturients were enrolled in the two groups: a-tES group (N = 62) and sham-tES group (N = 64). Treatment with tES resulted in significantly lower scores of anxiety compared with sham-tES (T2: P < 0.001; T3: P = 0.001). Moreover, the a-tES groups showed a significant reduction in depression scores (T2: P = 0.003; T3: P = 0.032).

CONCLUSION

In this randomized pilot study, tES treatment is efficacious in alleviating peripartum anxiety and depressive symptoms in women undergoing cesarean section and has been demonstrated to be a novel strategy for improving peripartum mental health disorders.

CLINICAL TRIAL REGISTRATION

[www.chictr.org.cn], identifier [ChiCTR2000040963].

Association between cortical thickness and anxiety measures: A scoping review

Cortical thickness has been increasingly studied in the context of structural-brain-behavior associations, such as anxiety; however, the literature is scattered across methods and research fields. This scoping review aims to summarize the available data concerning the association between cortical thickness and anxiety-related measures and identify the current research gaps. Searches were conducted in PubMed, PsycINFO/PsycARTICLES, Web of Science, OpenGrey and Networked Digital Library of Theses and Dissertations, and reference lists of key studies. Two researchers independently screened the abstracts and full-text reports according to the eligibility criteria, as well as extracted and charted the data. Quantitative and descriptive syntheses were conducted. The included publications (n = 18) reported cross-sectional studies, and 17 used surface-based approaches to estimate cortical thickness. Differences in regional cortical thickness were found to be associated with different anxiety-related measures/processes. Brain regions of interest include the medial orbitofrontal cortex, the ventromedial prefrontal cortex, the insula, the temporo-parietal areas, and the anterior cingulate cortex. However, caution should be warranted when interpreting the available results, as there is high variability in the field across anxiety-related measures, distinctive anxiety disorders, and data processing conditions and analysis. More research into this association is needed, to replicate and clarify existing findings.

Increased medial prefrontal cortical thickness and resilience to traumatic experiences in North Korean refugees

Little is known regarding structural brain changes in traumatized refugees and the association with psychopathology. In the present study, the cortical thickness in North Korean refugees and the association with psychological symptoms were explored. North Korean refugees with lifetime post-traumatic stress disorder (PTSD group, n = 27), trauma-exposed North Korean refugees without lifetime PTSD (trauma-exposed control (TEC) group, n = 23), and healthy South Korean controls without traumatic experiences (HC group, n = 51) completed questionnaires assessing depression, anxiety, somatization, and PTSD symptoms. The cortical thickness was measured by magnetic resonance imaging (MRI) using FreeSurfer. Age- and sex-adjusted cortical thickness of the right medial prefrontal cortex (mPFC) was greater in the TEC group than in the HC group. However, significant differences were not observed between the PTSD and HC groups. Increased right mPFC thickness was significantly correlated with less anxiety and somatization after controlling for age and sex in the TEC group, but not in the PTSD or HC groups. North Korean refugees who did not develop PTSD after trauma showed increased right mPFC thickness, which was associated with less severe psychiatric symptoms. These findings indicate that increased mPFC thickness might have helped to reduce PTSD and psychiatric symptoms after trauma, and likely reflects resilience achieved by potentially enhancing emotional regulation in the mPFC.

Cortical thickness and resting-state cardiac function across the lifespan: A cross-sectional pooled mega-analysis

Understanding the association between autonomic nervous system [ANS] function and brain morphology across the lifespan provides important insights into neurovisceral mechanisms underlying health and disease. Resting-state ANS activity, indexed by measures of heart rate [HR] and its variability [HRV] has been associated with brain morphology, particularly cortical thickness [CT]. While findings have been mixed regarding the anatomical distribution and direction of the associations, these inconsistencies may be due to sex and age differences in HR/HRV and CT. Previous studies have been limited by small sample sizes, which impede the assessment of sex differences and aging effects on the association between ANS function and CT. To overcome these limitations, 20 groups worldwide contributed data collected under similar protocols of CT assessment and HR/HRV recording to be pooled in a mega-analysis (N = 1,218 (50.5% female), mean age 36.7 years (range: 12-87)). Findings suggest a decline in HRV as well as CT with increasing age. CT, particularly in the orbitofrontal cortex, explained additional variance in HRV, beyond the effects of aging. This pattern of results may suggest that the decline in HRV with increasing age is related to a decline in orbitofrontal CT. These effects were independent of sex and specific to HRV; with no significant association between CT and HR. Greater CT across the adult lifespan may be vital for the maintenance of healthy cardiac regulation via the ANS-or greater cardiac vagal activity as indirectly reflected in HRV may slow brain atrophy. Findings reveal an important association between CT and cardiac parasympathetic activity with implications for healthy aging and longevity that should be studied further in longitudinal research.

Differences in cortical thinning across development among individuals with and without anxiety disorders

BACKGROUND

Anxiety is associated with aberrant patterns of cortical thickness in regions implicated in emotion regulation. However, few studies have examined cortical thickness differences between individuals with anxiety and healthy controls (HCs) across development, particularly during childhood when cortical thinning begins and anxiety risk increases. A better understanding of age-related changes in cortical thickness patterns among anxious individuals is essential to develop plausible targets for early identification.

METHODS

The current study examined how age impacted differences in cortical thickness patterns between HCs and anxious individuals. Participants included 233 individuals (ages 7-35) with a current anxiety disorder (n = 149) or no lifetime history of psychopathology (n = 84). Cortical thickness of regions that are implicated in emotion regulation (ventromedial prefrontal cortex [vmPFC], rostral anterior cingulate [rACC], and insula) were assessed.

RESULTS

All regions showed significant thinning with age, except left rACC and right insula. However, rates of thinning differed among anxious and HC participants, with anxious participants demonstrating slower rates of right vmPFC thinning. Regions of significance analyses indicated that anxious, relative to HC, participants exhibited thinner right vmPFC before age 11, but thicker right vmPFC after age 24.

CONCLUSIONS

Current findings suggest that anxious individuals do not demonstrate normative right vmPFC cortical thinning, which may lead them to exhibit both thinner vmPFC in middle childhood and thicker vmPFC in adulthood compared with HCs. These findings may provide plausible targets for identification of anxiety risk that differ based on developmental stage.

Cortical Thickness in Migraine: A Coordinate-Based Meta-Analysis

Cortical thickness (CTh) via surface-based morphometry analysis is a popular method to characterize brain morphometry. Many studies have been performed to investigate CTh abnormalities in migraine. However, the results from these studies were not consistent and even conflicting. These divergent results hinder us to obtain a clear picture of brain morphometry regarding CTh alterations in migraine. Coordinate-based meta-analysis (CBMA) is a promising technique to quantitatively pool individual neuroimaging studies to identify consistent brain areas involved. Electronic databases (PubMed, EMBASE, Web of Science, China National Knowledge Infrastructure, WanFang, and SinoMed) and other sources (bioRxiv and reference lists of relevant articles and reviews) were systematically searched for studies that compared regional CTh differences between patients with migraine and healthy controls (HCs) up to May 15, 2020. A CBMA was performed using the Seed-based d Mapping with Permutation of Subject Images approach. In total, we identified 16 studies with 17 datasets reported that were eligible for the CBMA. The 17 datasets included 872 patients with migraine (average sample size 51.3, mean age 39.6 years, 721 females) and 949 HCs (average sample size 59.3, mean age 44.2 years, 680 females). The CBMA detected no statistically significant consistency of CTh alterations in patients with migraine relative to HCs. Sensitivity analysis and subgroup analysis verified this result to be robust. Metaregression analyses revealed that this CBMA result was not confounded by age, gender, aura, attack frequency per month, and illness duration. Our CBMA adds to the evidence of the replication crisis in neuroimaging research that is increasingly recognized. Many potential confounders, such as underpowered sample size, heterogeneous patient selection criteria, and differences in imaging collection and methodology, may contribute to the inconsistencies of CTh alterations in migraine, which merit attention before planning future research on this topic.

Heart Rate Variability Moderates the Association Between Beliefs About Worry and Generalized Anxiety Disorder Symptoms

Paradoxically, some individuals who experience pathological worry also have good capacity for top-down control over their thoughts. Why such individuals would nevertheless worry excessively remains unclear. One explanation is suggested by research showing that those experiencing pathological worry are set apart from healthy controls by their beliefs that worry has utility and that effective worrying requires them to consider all possibilities before terminating a worry bout. This suggests that worriers with good capacity for cognitive control may engage in prolonged worry because they believe it is adaptive to do so. In a sample of 109 college students, among whom individuals reporting pathological worry were overrepresented, we tested this hypothesis using an objective index of top-down control capacity (i.e., resting vagally mediated heart rate variability [vmHRV]) and self-report measures of beliefs about worry and generalized anxiety disorder (GAD) symptom severity/status. As predicted, GAD symptom severity and vmHRV interacted to predict beliefs about worry. Specifically, high GAD symptoms were most strongly associated with beliefs that worry has utility at higher levels of vmHRV. Furthermore, this pattern was mostly a function of the belief that worry serves to distract the worrier from more emotional things. Similarly, high GAD symptoms were most strongly associated with endorsement of an ‘as many as can’ (AMAC) problem-solving rule when vmHRV was high. From the opposite perspective, both worry utility beliefs and AMAC rule endorsement were associated with the highest GAD symptom severity at higher levels of vmHRV. This was also true for the belief that worry distracts from more emotional things predicting analog GAD status. These results suggest that worriers who have higher levels of top-down control capacity may initiate and persist in worry, at least initially, because they value it. However, why they nevertheless rate their worry as excessive and uncontrollable is an important question for future research.

Transcranial direct current stimulation for the treatment of generalized anxiety disorder: A randomized clinical trial

BACKGROUND

Generalized anxiety disorder (GAD) is a common condition with current treatments being only moderately effective. Non-invasive brain stimulation techniques might provide a novel approach for treating GAD. Transcranial direct current stimulation (tDCS) has shown promising efficacy and tolerability for major depression but has not been investigated for GAD yet. Thus, we investigated the effects of tDCS on patients with GAD.

METHODS

We conducted a pilot, double-blind, randomized, sham-controlled trial on 30 GAD patients. Five sessions of tDCS (2 mA, 20 min, anode over the left dorsolateral prefrontal cortex and cathode over the right supraorbital cortex) were performed. Anxiety was the primary outcome and it was measured by the Hamilton Anxiety Rating Scale and the Beck Anxiety Inventory. Secondary outcomes were accessed by the Lipp Inventory of Stress Symptoms for Adults, Positive and Negative Affect Schedule, and the Beck Depression Inventory (BDI). Data were examined at baseline, after the 5th day of intervention, and at 1-week follow-up.

RESULTS

Thirty patients finished the study. There were no significant improvements in anxiety, mood symptoms of stress, affectivity or depression. Anodal stimulation of the left DLPFC showed significant improvements in physical symptoms of stress in GAD patients.

LIMITATIONS

Additional tDCS sessions could have resulted in larger tDCS effects.

CONCLUSION

Five sessions of anodal tDCS over the DLPFC did not improve the main outcomes for GAD patients, although physical symptoms of stress were improved. The role of tDCS in GAD should be explored in larger patient samples using different parameters.

Tuning of brain-autonomic coupling by prior threat exposure: Implications for internalizing problems in Mexican-origin adolescents

Exposure to threat increases the risk for internalizing problems in adolescence. Deficits in integrating bodily cues into representations of emotion are thought to contribute to internalizing problems. Given the role of the medial prefrontal cortex in regulating bodily responses and integrating them into representations of emotional states, coordination between activity in the medial prefrontal cortex and autonomic nervous system responses may be influenced by past threat exposure with consequences for the emergence of internalizing problems. A sample of 179 Mexican-origin adolescents (88 female) reported on neighborhood and school crime, peer victimization, and discrimination when they were 10-16 years old. At age 17, participants underwent a functional neuroimaging scan during which they viewed pictures of emotional faces while respiratory sinus arrhythmia (RSA) and skin conductance responses were measured. Adolescents also reported symptoms of internalizing problems. Greater exposure to threats across adolescence was associated with more internalizing problems. Threat exposure was also associated with stronger negative coupling between the ventromedial prefrontal cortex and RSA. Stronger negative ventromedial prefrontal cortex-RSA coupling was associated with fewer internalizing problems. These results suggest the degree of coordinated activity between the brain and parasympathetic nervous system is both enhanced by threat experiences and decreased in adolescents with more internalizing problems.

Psychophysiological Markers of Fear and Anxiety

PURPOSE OF REVIEW

The purpose of this paper is to provide a current review of the recent literature (2015-2018) on psychophysiological markers of fear and anxiety.

RECENT FINDING

Relative to healthy controls, fear-based disorders are characterised by heightened physiological reactivity to circumscribe threat salient stimuli, whereas anxiety-related disorders are associated with a more blunted pattern of physiological reactivity. Fear and anxiety disorders are marked by abnormal patterns of physiological reactivity, characterised by hyper- and hypo-reactivity in response to stimuli varying in threat salience.