This is a randomized controlled trial examining the efficacy and neural mechanisms of a standardized Mindfulness Intervention for Emotional Distress (MIED) in adults with subclinical emotional distress. One hundred and sixty participants will be randomly assigned to either an 8-week MIED program or an 8-week Progressive Muscle Relaxation (PMR) active control. The primary aim is to evaluate whether MIED reduces anxiety symptoms and reshapes multilevel emotional processing as measured by multimodal EEG (resting-state FAA/theta, Fast Periodic Visual Stimulation, and event-related potentials). Assessments occur at baseline (T1), post-intervention (T2), and 1-month follow-up.
Background. Emotional distress is a subclinical mental health condition characterized by persistent anxiety, depression, stress, and emotion dysregulation. Mindfulness interventions have shown efficacy across transdiagnostic emotional disorders, yet their neurocognitive mechanisms remain incompletely understood. Objective. This study aims to (1) verify the dynamic intervention effects of MIED on emotional distress; (2) reveal neuroplastic changes across multiple levels of emotional processing; (3) explore associations between neural changes and symptom improvement; and (4) examine whether strategy acquisition is linked to neural remodeling. Design. This is a two-arm, parallel-group, randomized controlled trial with single (outcomes assessor) blinding. Participants (N = 160) aged 18-50 with elevated psychological distress (K10 \> 21) will be randomized (1:1; block sizes 4 and 6) to: Experimental arm: MIED - 8 weeks of weekly 2.5-hour group sessions plus daily 15-minute app-based（IMIED） home practice. Active comparator arm: PMR - 8 weeks of structurally matched weekly 2.5-hour group sessions plus daily 15-minute audio home practice. Assessments. Baseline (T1), post-intervention (T2, within 2 weeks after Week 8), and 1-month follow-up (online). During the intervention, brief online tracking (GAD-7, PHQ-9) occurs at Weeks 2, 4, and 6. Neuroimaging. Multimodal EEG includes: (a) 5-minute resting-state EEG (FAA, theta power); (b) Fast Periodic Visual Stimulation (FPVS; 6 Hz base frequency, 1.2 Hz oddball for emotional faces) to index automatic emotional processing; (c) Task-based ERP ( LPP at 400-800 ms ) during emotional picture rating to index controlled emotional processing. Primary Mechanistic Outcome. LPP early-window (400-800 ms) mean amplitude under negative stimulus conditions. Statistical Analysis. Primary efficacy analyses will use linear mixed-effects models (LMM) under the intention-to-treat (ITT) principle. Missing data will be handled by restricted maximum likelihood (REML) assuming MAR, with multiple imputation as a sensitivity analysis. Hierarchical multiple comparison control: primary outcome (GAD-7) at α = 0.05 (two-sided); key secondary outcome (PHQ-9) reported with nominal and corrected p-values; remaining psychological and EEG measures corrected by Benjamini-Hochberg FDR.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
160
A standardized 8-week transdiagnostic mindfulness intervention (MIED) based on the Unified Protocol and contemporary mindfulness theory. Participants attend weekly 2.5-hour group sessions and complete daily 15-minute home practice via a mobile app (iMIED). Core practices include mindful breathing, body scan, mindful walking, and loving-kindness meditation. The program emphasizes four key strategies: engagement with life, distress tolerance, cognitive flexibility, and emotion-driven behavioral regulation. All sessions follow a structured manual to ensure fidelity.
A structured 8-week Progressive Muscle Relaxation program matched to MIED in frequency, duration, and format. Participants attend weekly 2.5-hour group sessions and complete daily 15-minute audio-guided home practice. The program progresses from systematic tension-release of major muscle groups to full-body relaxation, controlling for non-specific therapeutic factors (group support, time, expectancy). All sessions are manualized to ensure consistent delivery.
Peking University, School of Psychological and Cognitive Sciences
Beijing, Beijing Municipality, China
RECRUITINGGeneralized Anxiety Disorder-7（GAD-7）
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).
Time frame: Baseline (T1, Week 0), Week 2, Week 4, Week 6, post-intervention (T2, Week 8), and 1-month follow-up (Week 12)
Patient Health Questionnaire（PHQ-9）
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).
Time frame: Baseline (T1, Week 0), Week 2, Week 4, Week 6, post-intervention (T2, Week 8), and 1-month follow-up (Week 12)
Five Facet Mindfulness Questionnaire-20 (FFMQ-20)
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).
Time frame: Baseline (T1，week 0) and post-intervention (T2, Week 8)
Distress Tolerance Scale (DTS)
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).
Time frame: Baseline (T1，week 0) and post-intervention (T2，week 8)
Cognitive Flexibility Inventory (CFI)
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).
Time frame: Baseline (T1，week0) and post-intervention (T2，week8)
Excessive Emotional Behavior Scale (EEBS)
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.
Time frame: Baseline (T1，week 0) and post-intervention (T2，week8)
Engagement with Life Scale (ELS)
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.
Time frame: Baseline (T1，week0) and post-intervention (T2，week8)
Chinese Perceived Stress Scale (CPSS)
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).
Time frame: baseline（T1，week 0），post-intervention（T2，week8）
Late Positive Potential (LPP) early window (400-800 ms)
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.
Time frame: Baseline (T1，week 0) and post-intervention (T2，week 8)
Frontal Alpha Asymmetry (FAA)
Frontal Alpha Asymmetry (FAA; 8-13 Hz log-transformed alpha power difference) is a resting-state EEG measure of frontal hemispheric asymmetry, 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 during a 5-minute resting-state EEG recording. The primary specification is FAAln = ln(F4) - ln(F3), using absolute alpha power at F3/F4. As an exploratory specification, FAAlnrel = ln\[rel(F4)\] - ln\[rel(F3)\] will also be examined, where rel denotes alpha power divided by total (1-45 Hz) power at the same electrode. This addition does not alter the primary specification and was made prior to any analysis of post-intervention EEG data and prior to unblinding of group allocation.
Time frame: Baseline (T1，week 0) and post-intervention (T2，week 8)
Frontal theta power
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.
Time frame: Baseline (T1，week 0) and post-intervention (T2，week 8)
Fast Periodic Visual Stimulation Signal-to-Noise Ratio (FPVS-SNR)
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.
Time frame: Baseline (T1，week 0) and post-intervention (T2，week 8)
Kessler Psychological Distress Scale (K10)
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).
Time frame: Baseline (T1，week 0) and post-intervention (T2, Week 8)]
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