Repetitive Transcranial Magnetic Stimulation Modulates Frontal and Temporal Time-Varying EEG Network in Generalized Anxiety Disorder: A Pilot Study

The Efficacy and Acceptability of Non-Invasive Brain Stimulation Interventions for Obsessive-Compulsive Disorder Management: A Network Meta-Analysis Based on 24 Stimulation Methods

INTRODUCTION

Despite the high lifetime prevalence and elevated disability rates, treatments for obsessive-compulsive disorder (OCD) have limited efficacy. Considering the abnormal connectivity in the cortical-striatal-thalamic-cortical loop circuits in OCD, several randomized controlled trials (RCTs) have addressed the efficacy of different non-invasive brain stimulation (NIBS) modalities for the management of OCD. However, these RCTs yielded inconclusive results.

METHODS

This network meta-analysis (NMA) included RCTs of NIBS interventions, such as transcranial direct current stimulation (tDCS) and various repetitive transcranial magnetic stimulation (rTMS), in OCD patients. The primary outcomes were changes in the overall severity of OCD and acceptability (i.e., dropout rates).

RESULTS

This NMA of 34 eligible RCTs (1089 participants) and 24 different NIBS interventions revealed that three NIBS interventions significantly improved overall OCD severity compared with sham controls, which were high-frequency rTMS over the dorsolateral prefrontal cortex (DLPFC) [mean difference (MD) = -10.81, 95% confidence intervals (95% CIs) = -20.80 to -0.82], high-frequency deep TMS over the dorsal medial prefrontal cortex/anterior cingulate cortex (dmPFC/ACC) (MD = -9.74, 95% CIs = -16.42 to -3.06), and low-frequency rTMS over the right DLPFC (MD = -4.70, 95% CIs = -8.84 to -0.57).

CONCLUSIONS

This study highlighted that excitatory stimulation over the dmPFC/ACC and bilateral DLPFC, or inhibitory stimulation over the right DLPFC, was associated with significant improvements in overall OCD severity. Further large-scale RCTs with longer follow-up periods are needed to investigate the true impact of NIBS-based intervention to manage OCD.

TRIAL REGISTRATION

PROSPERO: CRD42023394953.

Enhanced diagnostics for generalized anxiety disorder: leveraging differential channel and functional connectivity features based on frontal EEG signals

Generalized Anxiety Disorder (GAD) is a chronic anxiety condition characterized by persistent excessive worry, anxiety, and fear. Current diagnostic practices primarily rely on clinicians' subjective assessments and experience, highlighting a need for more objective and reliable methods. This study collected 10-minute resting-state electroencephalogram (EEG) from 45 GAD patients and 36 healthy controls (HC), focusing on six frontal EEG channels for preprocessing, data segmentation, and frequency band division. Innovatively, this study introduced the "Differential Channel" method, which enhances classification performance by enhancing the information related to anxiety from the data, thereby highlighting signal differences. Utilizing the preprocessed EEG signals, undirected functional connectivity features (Phase Lag Index, Pearson Correlation Coefficient, and Mutual Information) and directed functional connectivity features (Partial Directed Coherence) were extracted. Multiple machine learning models were applied to distinguish between GAD patients and HC. The results show that the Deep Forest classifier achieves excellent performance with a 12-second time window of DiffFeature. In particular, the classification of GAD and HC was successfully obtained by combining OriFeature and DiffFeature on Mutual Information with a maximum accuracy of 98.08%. Furthermore, it was observed that undirected functional connectivity features significantly outperformed directed functional connectivity when fewer frontal channels were used. Overall, the methodologies developed in this study offer accurate and practical identification strategies for the early screening and clinical diagnosis of GAD, offering the necessary theoretical and technical support for further enhancing the portability of EEG devices.

Altered Functional Brain Network Structure between Patients with High and Low Generalized Anxiety Disorder

To investigate the differences in functional brain network structures between patients with a high level of generalized anxiety disorder (HGAD) and those with a low level of generalized anxiety disorder (LGAD), a resting-state electroencephalogram (EEG) was recorded in 30 LGAD patients and 21 HGAD patients. Functional connectivity between all pairs of brain regions was determined by the Phase Lag Index (PLI) to construct a functional brain network. Then, the characteristic path length, clustering coefficient, and small world were calculated to estimate functional brain network structures. The results showed that the PLI values of HGAD were significantly increased in alpha2, and significantly decreased in the theta and alpha1 rhythms, and the small-world attributes for both HGAD patients and LGAD patients were less than one for all the rhythms. Moreover, the small-world values of HGAD were significantly lower than those of LGAD in the theta and alpha2 rhythms, which indicated that the brain functional network structure would deteriorate with the increase in generalized anxiety disorder (GAD) severity. Our findings may play a role in the development and understanding of LGAD and HGAD to determine whether interventions that target these brain changes may be effective in treating GAD.

Update on treatments for anxiety-related disorders

PURPOSE OF REVIEW

This review examines recent evidence that informs the treatment of anxiety-related disorders.

RECENT FINDINGS

In addition to selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), and benzodiazepines, agomelatine has demonstrated efficacy in treating generalized anxiety disorder (GAD). Other novel products, such as ketamine, psilocybin and cannabidiol, are in the process of gathering evidence in support of the treatment of anxiety disorders. In psychological therapy, various psychological treatments for anxiety disorders, such as mindfulness-based intervention, acceptance and commitment therapy, psychodynamic therapy, emotion-focused therapy and dialectical behavioural therapy, have been tried. Still, most therapies have not proven superior to cognitive behavioural therapy (CBT). In very preliminary findings: Repetitive transcranial magnetic stimulation (rTMS) was effective in GAD; transcranial direct current stimulation (tDCS) was effective for social anxiety disorder (SAD) and GAD and augmented exposure therapy for specific fears. Internet and mobile-based interventions have comparable efficacy to face-to-face therapy.

SUMMARY

Pharmacotherapy of anxiety disorders is expanding to novel products. Despite trying other psychological therapies for anxiety disorders, most therapies were comparable to but not superior to CBT. rTMS and tDCS were also used and show early promise for GAD, but further studies are needed. Most internet or mobile app based psychological therapies were based on CBT, and some can be considered as alternatives to in-person face-to-face therapy.