Transcranial Electrical Stimulation for Comorbid Depression and Chronic Pain

Description:

The BPI is a validated self-administered questionnaire that assesses the severity of pain and its impact on daily functioning. The pain intensity subscale consists of four items rating pain at its "worst," "least," "average," and "current" (right now). Each item is rated on a 0 to 10 numeric rating scale. Higher scores mean a worse outcome.

The Minimal Clinically Important Difference (MCID) is defined as a reduction of ≥ 1 point from baseline in the BPI pain intensity score. The outcome is the proportion of participants in each group who achieve this MCID threshold at each follow-up time point.

The HAMD-17 is a 17-item clinician-rated scale assessing depression severity. Items are rated on 3- or 5-point scales, with total scores ranging from 0 to 52. Higher scores mean a worse outcome (greater depression severity).

The outcome is the percentage reduction in HAMD-17 total score from baseline at each follow-up time point, calculated using the formula:

[(Baseline score - Follow-up score) / Baseline score] × 100%

A positive percentage indicates improvement (reduction in depressive symptoms).

The Hamilton Depression Rating Scale (HAMD-17) is a 17-item clinician-rated scale assessing depression severity. Items are rated on 3- or 5-point scales, with total scores ranging from 0 to 52. Higher scores indicate greater depression severity (worse outcome). The outcome is the absolute change in the total score from baseline at each follow-up time point, calculated as: [(Baseline score) - (Follow-up score)]. A positive change value indicates improvement (reduction in depressive symptoms). No pre-defined clinically meaningful threshold is applied to this continuous outcome; it is reported as the mean absolute change per group.

The Pain Catastrophizing Scale (PCS) is a 13-item self-reported questionnaire. Each item is rated on a 5-point Likert scale from 0 (not at all) to 4 (all the time), with total scores ranging from 0 to 52. Higher scores indicate higher levels of pain catastrophizing (worse outcome). The outcome is the absolute change in the total score from baseline at each follow-up time point, calculated as: [(Baseline score) - (Follow-up score)]. A positive change value indicates improvement (reduction in pain catastrophizing).

The GAD-7 is a 7-item self-report scale (0-21, higher scores = worse outcome) assessing anxiety symptoms over the past two weeks. The outcome is the absolute change in the total score from baseline at each follow-up time point, calculated as: [(Baseline score) - (Follow-up score)].

The Clinical Global Impression (CGI) scale consists of two clinician-rated subscales assessing overall treatment response:

CGI-Severity (CGI-S): Rates the severity of the patient's illness on a 7-point scale from 1 (normal, not at all ill) to 7 (among the most extremely ill patients). Higher scores mean a worse outcome.

CGI-Improvement (CGI-I): Rates the patient's improvement compared to baseline on a 7-point scale from 1 (very much improved) to 7 (very much worse). This subscale is only assessed at post-baseline time points. Lower scores mean a better outcome (greater improvement).

The outcome is the change from baseline in CGI-S score at each follow-up time point, and the CGI-I score at each post-baseline time point.

Resting-state functional connectivity (rs-FC) of the dorsolateral prefrontal cortex (DLPFC) is assessed using resting-state functional magnetic resonance imaging (rs-fMRI). The primary measurement is the change in seed-based functional connectivity strength between the DLPFC and its target network regions (e.g., parietal cortex, default mode network nodes), quantified as Fisher-transformed correlation coefficients (z-values) from a priori defined regions of interest. Higher z-values indicate stronger positive functional connectivity; lower or negative values indicate weaker or anticorrelated connectivity. Structural MRI (sMRI) is acquired for co-registration and normalization purposes.

Metabolite profiles are measured using untargeted liquid chromatography-mass spectrometry (LC-MS) in plasma-derived brain-enriched exosomes. Changes in metabolite profiles from baseline to post-intervention are assessed using multivariate partial least squares discriminant analysis (PLS-DA). The primary comparison is the separation distance (e.g., Q² or R² values) between baseline and post-intervention clusters, with positive values indicating greater separation between the two time points. This is an exploratory outcome to identify potential metabolic biomarkers and generate hypotheses related to the mechanisms of tACS/tDCS action. Results will be reported descriptively and are not part of the primary confirmatory analysis.

This exploratory outcome measures the change from baseline in the BPI Pain Intensity score after 10 sessions of active tACS in the open-label arm. Data are reported descriptively as individual change values, mean change, standard deviation, and within-group effect size (Cohen's d) . No formal hypothesis testing is planned; the results will inform effect size estimation for future trial planning.

This exploratory outcome measures the change from baseline in HAMD-17 total score after 10 sessions of active tACS in the open-label arm. Data are reported descriptively as individual change values, mean change, standard deviation, and within-group effect size (Cohen's d). No formal hypothesis testing is planned; the results will inform effect size estimation for future trial planning.

This exploratory outcome measures the change from baseline in GAD-7 total score after 10 sessions of active tACS in the open-label arm. Data are reported descriptively as individual change values, mean change, standard deviation, and within-group effect size (Cohen's d). No formal hypothesis testing is planned. GAD-7 scores will also be explored as a covariate in pain outcome analyses.

Resting-state EEG is recorded for 5 minutes with eyes open and 5 minutes with eyes closed using a 64-channel EEG system. The primary measure is the change from baseline in spectral power (absolute and relative) across frequency bands (delta: 1-4 Hz, theta: 4-8 Hz, alpha: 8-12 Hz, beta: 12-30 Hz, gamma: 30-50 Hz), with a focus on the alpha band (8-12 Hz) due to the 10 Hz tACS intervention. Data are analyzed descriptively without formal hypothesis testing.

Task-state EEG is recorded while participants perform a cognitive task (e.g., working memory or attention task). The primary measure is the change from baseline in event-related potential (ERP) components and task-related spectral power changes (event-related desynchronization/synchronization). Data are analyzed descriptively without formal hypothesis testing.

Resting-state EEG functional connectivity is assessed using coherence and phase-locking value (PLV) between electrode pairs, with a focus on the alpha band and the DLPFC region. Data are analyzed descriptively without formal hypothesis testing.