Mindfulness Intervention for Emotional Distress: An EEG Study

Effects and Multimodal EEG Mechanisms of an 8-week Mindfulness Intervention for Emotional Distress: A Randomized Controlled Trial

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.

Inclusion Criteria:

• Adults aged 18-50 years Kessler Psychological Distress Scale (K10) score > 21 No systematic mindfulness or progressive muscle relaxation practice in the past 6 months (frequency < 1 time per week) Normal or corrected-to-normal vision Voluntary participation with signed informed consent

Exclusion Criteria:

• Prior diagnosis of schizophrenia, bipolar disorder, or other severe mental disorders by a psychiatrist Suicidal plan, self-injury, or need for emergency psychological crisis intervention in the past month Currently receiving systematic psychotherapy or participating in other psychological intervention programs Started psychiatric medication within the past 3 months or on an unstable medication dosage History of epilepsy, severe brain injury, or other neurological disorders that may affect EEG measurement Severe vision or hearing impairment or other conditions preventing completion of study procedures