This clinical trial aims to determine whether beta-band transcranial alternating current stimulation (tACS) can improve impulse inhibition in adolescents with non-suicidal self-injury (NSSI) and to evaluate its safety. The primary questions it seeks to answer are:
* Can beta-band tACS significantly reduce the frequency of self-injury and scores on impulsivity scales in adolescents with NSSI? * What discomfort or medical issues may participants experience during tACS intervention?
Researchers will compare beta-band tACS with sham stimulation (a procedure that mimics the real stimulation without delivering effective current) to verify its efficacy.
Participants will:
* Receive two sessions of either tACS or sham stimulation daily, spaced 4 hours apart, for 7 consecutive days (14 sessions in total). * Undergo scale assessments, behavioral tasks, and eye-tracking tests before and after the intervention. * Record any self-injury episodes and adverse reactions, with continuous monitoring and psychological support provided by a professional team.
1) Meet the proposed diagnostic criteria for non-suicidal self-injury (NSSI) in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), with ≥5 documented self-injury episodes and at least one incident within the past month as assessed by the Adolescent Non-Suicidal Self-Injury Assessment Questionnaire (ANSAQ); 2) Aged 12-18 years; 3) Right-handed; 4) Possess formal education experience sufficient to comprehend experimental protocols; 5) Normal or corrected-to-normal binocular visual acuity; 6) Voluntarily participate with legal guardians providing written informed consent.
1) Montreal Cognitive Assessment (MoCA) score < 26; 2) History of suicide attempt(s); 3) Medical history of epilepsy, brain surgery, intracranial tumors, metal implants in the skull, or clinically significant head trauma; 4) History of substance use disorder, brain injury, severe somatic diseases, psychiatric disorders, or comorbid DSM-5 psychiatric conditions; 5) Prior receipt of transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), or repetitive transcranial magnetic stimulation (rTMS) within the past 3 months
Parallel
Beta-frequency transcranial alternating current stimulation
DeviceActive beta-frequency transcranial alternating current stimulation: 20 Hz tACS delivered through a 4×1-ring high-definition electrode montage centered on left DLPFC (F3), 2 mA peak-to-peak, 100 % intensity, gradually ramped up over 30 s, maintained for 20 min, then ramped down over 30 s; two sessions per day with at least 4 h between sessions, repeated for 7 consecutive days (14 total sessions).
sham beta-frequency transcranial alternating current stimulation
DeviceSham transcranial alternating current stimulation: identical 4×1-ring high-definition electrode montage centered on left DLPFC (F3), 2 mA peak-to-peak current ramped up over 30 s and immediately ramped down to 0 mA, followed by 19.5 min of no stimulation to match the 20-min session duration of active tACS; delivered twice daily (≥4 h apart) for 7 consecutive days (14 total sessions).
Adolescent Non-suicidal Self-injury Assessment Questionnaire (ANSAQ) reduction in the frequency of self-injury
The ANSAQ is a brief, self-report tool specifically designed for adolescents aged 12-18 to quantify non-suicidal self-injury (NSSI) over the past year. It is used both to screen for clinically relevant self-harm and to track changes in self-injury frequency after an intervention.
UPPS-P Impulsive Behavior Scale (UPPS-P)
The UPPS-P is a 59-item self-report questionnaire that measures five distinct facets of impulsivity: Negative Urgency, (lack of) Premeditation, (lack of) Perseverance, Sensation Seeking, and Positive Urgency. Each item is rated on a 4-point Likert scale from 1 (agree strongly) to 4 (disagree strongly); items are reverse-scored so that higher scores indicate greater impulsivity.
Brief Barratt Impulsiveness Scale (BBIS)
The BBIS is an 8-item, self-report subset of the well-known Barratt Impulsiveness Scale. Each item (e.g., "I act on the spur of the moment") is answered on a 4-point scale: 1 = rarely/never, 2 = occasionally, 3 = often, 4 = almost always/always. Total scores range 8-32; higher scores indicate greater impulsivity.
Eye movement index-fixation time
Recorded with an SMI-RED eye-tracker while participants freely view 60 pictures in the NSSI-cue reactivity paradigm. Each picture (tool cue, use cue, association cue, or neutral cue) is presented for 4 000 ms. The Region of Interest (ROI) is the entire picture area. "Fixation time" is the total duration (ms) that gaze remains within this ROI during picture presentation. Values are averaged across all cue types (or separately for NSSI-relevant vs. neutral cues) at baseline (Day 0) and post-intervention (Day 8). A ≥ 20 % reduction in total fixation time on NSSI-relevant cues relative to baseline is defined as a clinically relevant improvement in inhibitory control.
Hamilton Depression Scale (HAMD-17) score
The HAMD-17 is a clinician-rated scale of depressive symptoms. Seventeen items (mood, sleep, guilt, etc.) are scored 0-2 or 0-4; total ranges 0-52. Higher scores indicate more severe depression.
Hamilton Anxiety Scale (HAMA-14) score
The HAMA-14 is a clinician-rated scale that assesses the severity of anxiety symptoms. It contains 14 items covering psychic and somatic anxiety; each item is scored 0 (not present) to 4 (very severe), giving a total range of 0-56, with higher scores indicating greater anxiety.
the score of Moca
A 30-point clinician-administered screen covering eight cognitive domains: visuospatial/executive, naming, memory, attention, language, abstraction, delayed recall, and orientation. Each correct response earns 1 point; scores 0-30 with ≥ 26 considered normal. Used in this study to exclude participants with cognitive impairment (\< 26).
the score of TAS-20
Self-report measure of alexithymia with 20 items rated 1-5, yielding three subscales: Difficulty Identifying Feelings, Difficulty Describing Feelings, and Externally Oriented Thinking. Total score 20-100; ≥ 61 indicates clinically significant alexithymia.
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