The Effect of Transcranial Direct Current Stimulation (tDCS) in Improving Emotion Health

Utilizing Transcranial Direct Current Stimulation (tDCS) to Alleviate Subthreshold Depression Via Distinct Positive and Negative Emotion Pathways

The goal of this clinical trial is to investigate how transcranial direct current stimulation (tDCS) affects emotion functions in young adults aged 18-35 from the local community, including both male and female participants. The main question[s] it aims to answer are:

• Does tDCS improve emotional functions, such as mood regulation and motivation, in individuals with subthreshold depression (StD)?
• Can tDCS enhance emotional regulation compared to a sham stimulation (placebo)?

Researchers will compare participants receiving tDCS on either the left dorsolateral prefrontal cortex (lDLPFC) or right ventrolateral prefrontal cortex (rVLPFC) with those receiving sham stimulation to see if tDCS has a stronger effect on emotional functions.

Participants will:

• Complete online and in-person screening to assess depressive symptoms using the Chinese version of the Beck Depression Inventory II (C-BDI-II) and be selected based on their depressive symptoms (C-BDI-II score ≥ 13).
• Be randomly assigned to one of three groups: lDLPFC tDCS, rVLPFC tDCS, or Sham control group (1:1:1 ratio).
• Receive 10 sessions of tDCS or Sham tDCS over 2 weeks, with each session lasting 20 minutes.
• Complete assessments at baseline, post-intervention, 1-month follow-up, and 3-month follow-up, with each assessment lasting 2-2.5 hours. This includes questionnaires and perform emotional and cognitive tasks.

Study Overview

• Status: Recruiting
• Conditions: Anhedonia; Subthreshold Depression; Positive Emotions; Negative Emotions
• Intervention / Treatment: Device: Transcranial Direct Current Stimulation; Device: Sham tDCS

• Study Type: Interventional
• Enrollment (Estimated): 90
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Associate Professor, Principle Investigator; Phone Number: +852-3917-8927; Email: rshao@hku.hk

Study Locations

• Hong Kong
  • Hong Kong, Hong Kong
    • Recruiting
    • The University of Hong Kong
    • Contact: Associate Professor, Principle Investigator; Phone Number: +852-3917-8927; Email: rshao@hku.hk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age 18-35 years
• Fluency in Cantonese or Mandarin
• Normal or corrected-to-normal vision and hearing
• IQ > 75% Quantile in Raven's SPM
• At least 9 years of formal education
• Right-handedness

Exclusion Criteria:

• Past or current major physical illness or psychiatric disorders
• Use of psychotropic medication in the past 6 months
• Pregnancy (for women)
• Any condition that prevents safe tDCS use (e.g., brain injury, implants)
• Previous participation in neuromodulation in the past 3 months

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: IDLPFC tDCS; This intervention is a 20 minutes per session, two-week tDCS neuromodulation of IDLPFC region (anode: F3, cathode: FP2) designed to reduce depressive symptoms via enhancing positive emotion functions, thereby reducing anhedonia.	Device: Transcranial Direct Current Stimulation; TDCS is a non-invasive, safe, inexpensive, convenient and effective method to modulate brain and emotion functions. During tDCS, a mild electric current is passed between the anodal and cathodal electrodes on the scalp, which respectively excites and inhibits local and downstream neuronal activity, as well as modulating interregional connectivity strength. Compared to other neurostimulation methods such as Transcranial Magnetic Stimulation, tDCS side effects tend to be milder and transient, even if being administered for multiple sessions, making it suitable to be widely applied on clinical and subclinical populations.; Other Names: tDCS
Experimental: rVLPFC tDCS; This intervention is a 20 minutes per session, two-week tDCS neuromodulation of rVLPFC region (anode: F6, cathode: FP1) designed to reduce depressive symptoms via regulating negative emotion functions, thereby reducing depressed mood.	Device: Transcranial Direct Current Stimulation; TDCS is a non-invasive, safe, inexpensive, convenient and effective method to modulate brain and emotion functions. During tDCS, a mild electric current is passed between the anodal and cathodal electrodes on the scalp, which respectively excites and inhibits local and downstream neuronal activity, as well as modulating interregional connectivity strength. Compared to other neurostimulation methods such as Transcranial Magnetic Stimulation, tDCS side effects tend to be milder and transient, even if being administered for multiple sessions, making it suitable to be widely applied on clinical and subclinical populations.; Other Names: tDCS
Sham Comparator: Sham tDCS; This is a 20 minutes per session, two-week Sham comparator of IDLPFC/rVLPFC region, participants will receive tDCS for 30 seconds at either IDLPFC/rVLPFC at the beginning of each session to stimulate real neuromodulation.	Device: Sham tDCS; The sham tDCS delivers actual stimulation for 30 seconds only, while providing similar psychological perceptions to participants as the real intervention. Thus, the sham tDCS serves as an active control condition to the tDCS interventions.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Depressive symptoms	The Beck Depression Inventory-II Chinese Version measures change in depressive symptoms. The total score range is 0-63, higher score indicates more severe depressive symptoms.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Affective trait	The Chinese Affect Scale measures changes in positive and negative affective traits. Both the positive affect and the negative affect subscales have a score range of 0-40, with higher scores indicating higher levels of positive affect trait and negative affect trait respectively.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Anhedonia severity	The dimensional anhedonia rating scale measures change in anhedonia severity on distinct physical/social domain. The scale comprises four subscales: Hobbies (4 items; score range 0-16), Food/Drink (4 items; score range 0-16), Social Activities (4 items; score range 0-16), and Sensory Experience (5 items; score range 0-20), with higher scores on each subscale indicating less anhedonia severity within the corresponding domain.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Anhedonia symptoms	The Chapman Physical/Social Anhedonia scales assess change in anhedonia symptoms in physical and social domains. The Chapman Physical Anhedonia Scale consists of 61 true-false items with a total score range of 0-61, and the Chapman Social Anhedonia Scale consists of 40 true-false items with a total score range of 0-40. For both scales, higher scores indicate higher levels of anhedonia.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Behavioural motivation trait	The Behavioural Activation and Inhibition Scale measures change in reward-driven approaching and punishment-driven avoidance tendencies. The Behavioural Inhibition System scale consists of 7 items with a score range of 7-28, with higher scores indicating higher behavioural inhibition. The Behavioural Activation System scale comprises three subscales: Drive (4 items; score range 4-16), Fun Seeking (4 items; score range 4-16), and Reward Responsiveness (5 items; score range 5-20). Higher scores on each BAS subscale indicate higher levels of behavioural activation within the corresponding domain.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Emotion regulation function	The Cognitive Emotion Regulation Questionnaire measures change in emotion regulation functions. The scale comprises nine subscales, Self-Blame, Acceptance, Rumination, Positive Refocusing, Refocus on Planning, Positive Reappraisal, Putting into Perspective, Catastrophising, and Other-Blame. Each consisting of 2 items with a score range of 2-10. Higher scores on each subscale indicate greater habitual use of emotion regulation strategy.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Coping to adversity	The Brief Coping Orientation to Problems Experienced inventory measures change in people's coping strategies to hardships. The problem-focused subscale consist of 8 items (score range 4-32). The emotion-focused subscale consists of 12 items (score range 4-46). The avoidant/dysfunctional coping subscale consists of 8 items (score range 4-32). In each subscale, higher scores indicate greater use of the corresponding coping strategy.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Reward sensitivity	The Temporal Experience of Pleasure Scale assesses change in sensitivity towards both anticipatory and consummatory pleasurable experience. The scale comprises four subscales: Abstract Anticipatory Pleasure (4 items; score range 4-24), Contextual Anticipatory Pleasure (5 items; score range 5-30), Abstract Consummatory Pleasure (6 items; score range 6-36), and Contextual Consummatory Pleasure (4 items; score range 4-24), with higher scores on each subscale indicating greater capacity to experience pleasure from reward.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Apathy symptom	The Apathy Evaluation Scale-Self measures change in emotional indifference and apathy (lack of motivation). The scale consists of 18 items, yielding a total score range of 0-54, with higher scores indicating greater emotional indifference and higher levels of apathy.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Perceived loneliness	The brief UCLA Loneliness Scale measures change in the participants' subjective loneliness. The scale consists of 6 items yielding a total score range of 6-24, with higher scores indicating higher levels of perceived loneliness.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Stress level	The 10-item Perceived Stress Scale measures change in perceived stressful experiences. The scale consists of 10 items yielding a total score range of 0-40, with higher scores indicating higher levels of perceived stress.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Emotion ratings of words	The Emotion Rating Task measures changes in participants' feeling and motivation to positive social, positive non-social, negative social and negative non-social word stimuli.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Instrumental behavioural motivation	The Monetary Incentive Delay task measures change in behavioural motivations to obtain rewards or to avoid punishment.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Emotional inhibition control	The Emotion Stroop task measures change in participants' inhibition control of emotional processing.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Cognitive control function	The colour stroop measures change in cognitive control and inhibition functions.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)
Working memory	The N-back task measures change in the participants' working memory capacity.	Baseline (Day 1), Post-Intervention (Day 15), 1-Month Follow-up (Day 45), 3-Month Follow-up (Day 105)

Collaborators and Investigators

• Sponsor: The University of Hong Kong
• Collaborators: Research Grants Council, Hong Kong

Study record dates

Study Major Dates

• Study Start (Actual): January 8, 2026
• Primary Completion (Estimated): September 1, 2027
• Study Completion (Estimated): September 1, 2027

Study Registration Dates

• First Submitted: December 6, 2025
• First Submitted That Met QC Criteria: December 19, 2025
• First Posted (Actual): January 6, 2026

Study Record Updates

• Last Update Posted (Actual): May 4, 2026
• Last Update Submitted That Met QC Criteria: April 28, 2026
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: Neuromodulation; Transcranial Direct Current Stimulation; Emotion; Subthreshold Depression
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Neurobehavioral Manifestations; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Anhedonia; Therapeutics; Behavioral Disciplines and Activities; Electric Stimulation Therapy; Convulsive Therapy; Psychiatric Somatic Therapies; Electroshock; Psychological Techniques; Transcranial Direct Current Stimulation
• Other Study ID Numbers: EA240670; 17600425 (Other Grant/Funding Number: Research Grants Council)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No