Mindfulness Intervention for Emotional Distress: An EEG Study

The GAD-7 is a 7-item self-report measure of anxiety symptom severity over the past 2 weeks. Total scores range from 0 to 21. The primary analysis examines the Group × Time interaction using linear mixed-effects models across all six assessment points (Weeks 0, 2, 4, 6, 8, and 12).

The Patient Health Questionnaire-9 (PHQ-9) is a 9-item self-report measure assessing the severity of depressive symptoms over the past two weeks. Total scores range from 0 to 27, with higher scores indicating more severe depressive symptoms (worse outcome).

The Five Facet Mindfulness Questionnaire-20 (FFMQ-20) is a 20-item self-report measure assessing trait mindfulness across five facets. Total scores range from 20 to 100, with higher scores indicating greater mindfulness (better outcome).

The Distress Tolerance Scale (DTS) is a 15-item self-report measure assessing an individual's perceived ability to tolerate and manage emotional distress. Total scores range from 15 to 75, with higher scores indicating greater distress tolerance (better outcome).

The Cognitive Flexibility Inventory (CFI) is a 20-item self-report measure assessing cognitive flexibility. Total scores range from 20 to 140, with higher scores indicating greater cognitive flexibility (better outcome).

EEBS is a self-report measure assessing the tendency to engage in excessive emotional behaviors in response to emotional distress. Higher scores indicate greater levels of excessive emotional behavior.

ELS is a self-report measure assessing the extent to which individuals engage in meaningful and valued life activities despite experiencing emotional distress. Higher scores indicate greater engagement with life.

The Chinese Perceived Stress Scale-14 (CPSS-14) is a 14-item self-report measure assessing perceived stress during the past month. Total scores range from 0 to 56, with higher scores indicating greater perceived stress (worse outcome).

Late Positive Potential (LPP; 400-800 ms mean amplitude) is an ERP component reflecting sustained controlled processing of emotional stimuli. Mean LPP amplitude within the 400-800 ms time window will be quantified at CPz, Cz, P3, Pz, and P4 during a 20-minute emotional picture rating task. Based on the best available evidence and theoretical rationale from previous mindfulness and emotion regulation studies, LPP was selected as a candidate mechanistic outcome.

Frontal Alpha Asymmetry (FAA; 8-13 Hz log-transformed alpha power difference) is a resting-state EEG measure reflecting hemispheric asymmetry in frontal cortical activity and has been associated with affective processing, emotion regulation, and approach-withdrawal motivational tendencies. FAA will be calculated as the log-transformed alpha power difference between homologous frontal electrode pairs (e.g., ln[F4] - ln[F3]) during a 5-minute resting-state EEG recording. Based on the best available evidence and theoretical rationale from previous mindfulness and emotion regulation studies, FAA was selected as a candidate mechanistic outcome.

Frontal theta power (4-8 Hz) is a resting-state EEG measure associated with cognitive control, attentional regulation, and emotion regulation. Absolute or relative theta power within the 4-8 Hz frequency band will be quantified from frontal electrodes (e.g., Fz, F3, and F4) during a 5-minute resting-state EEG recording. Based on the best available evidence and theoretical rationale from previous mindfulness and cognitive control studies, frontal theta power was selected as a candidate mechanistic outcome.

Fast Periodic Visual Stimulation Signal-to-Noise Ratio (FPVS-SNR) is an EEG-derived measure quantifying neural responses to periodically presented emotional visual stimuli. Change in FPVS-SNR from baseline to post-intervention will be assessed during the emotional fast periodic visual stimulation task.Based on the best available evidence and theoretical rationale, FPVS-SNR was selected as a candidate mechanistic outcome to assess changes in visual emotional processing following the intervention.

The Kessler Psychological Distress Scale (K10) is a 10-item self-report measure assessing non-specific psychological distress during the past four weeks. Total scores range from 10 to 50, with higher scores indicating greater psychological distress (worse outcome).

The MRAES-MBP is a self-report measure assessing meditation-related adverse events experienced during participation in mindfulness-based programs, including their occurrence and severity.

A simplified safety monitoring questionnaire administered biweekly to the PMR group to assess somatic discomfort and emotional reactions related to muscle relaxation practice.

A 6-item measure of intervention credibility and improvement expectancy, administered to assess and control for non-specific expectancy effects as a covariate in primary efficacy analyses.