The Impact of Beta-band Transcranial Alternating Current Stimulation (tACS) on Impulse Inhibition in Adolescents With Non-suicidal 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.

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.

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.

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.

During the NSSI cue-reactivity paradigm, an SMI-RED eye-tracker records gaze while 60 pictures (tool, use, association, or neutral cues) are each displayed for 4 000 ms. The entire picture is defined as the Region of Interest (ROI). "Fixation counts" is the total number of discrete fixations that fall within this ROI. The score is averaged across all pictures (or separately for NSSI-relevant vs. neutral cues) at baseline (Day 0) and after the 7-day intervention (Day 8). A ≥ 20 % reduction in fixation counts on NSSI-relevant cues from baseline indicates improved impulse inhibition.

In the computer-based Balloon Analog Risk Task (BART), participants are shown 30 virtual balloons one at a time. They press "F" to inflate (pump) each balloon; every pump increases potential earnings by ¥0.5 but also raises the risk of explosion. Explosion points are random (1-128 pumps, mean 64). Participants can press "J" at any time to stop inflating and bank the current reward. "Total number of balloon explosions" is the count of balloons that burst across all 30 trials. Higher numbers reflect greater risk-taking and poorer impulse control. The score is obtained at baseline (Day 0) and after the 7-day intervention (Day 8); a ≥ 20 % reduction in explosions from baseline is considered a clinically relevant improvement in inhibitory control.

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.

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.

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).

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.

The ERQ is a 10-item self-report scale that measures habitual use of two emotion-regulation strategies: Cognitive Reappraisal (6 items) and Expressive Suppression (4 items). Each item is rated on a 7-point Likert scale from 1 (strongly disagree) to 7 (strongly agree). Sub-scale scores are generated by summing respective items: Reappraisal range 6-42, Suppression range 4-28. Higher scores indicate more frequent use of the strategy. The scale shows good internal consistency (α ≥ .79) and 3-month test-retest reliability (r ≈ .69) in adolescents .

14-item self-report that gauges both protective (positive) and risk-related (negative) aspects of suicide ideation in adolescents. Items are rated 1-5; higher totals on the 6-item Positive Ideation sub-scale (range 6-30) indicate greater resilience, while higher totals on the 8-item Negative Ideation sub-scale (range 8-40) signal increased suicide risk.