Effects of taVNS Combined With tACS on 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. Higher frequencies indicate more severe NSSI behavior.

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. Total score: 32. Higher scores indicate greater impulsivity.

A free-viewing paradigm consisting of 60 images was employed, with eye movements recorded using an SMI-RED eye-tracking system. Each trial comprised a four-image array: three neutral stimuli and one NSSI-related stimulus, presented for 4000 ms. A dot-probe paradigm consisting of 204 trials was employed, with eye movements recorded using an SMI-RED eye-tracking system. Each trial comprised a pair of images: one neutral stimulus and one NSSI-related stimulus, presented for either 200 ms or 500 ms.The region of interest (ROI) was defined as the area containing the NSSI-related cue. 'Dwell time' was operationalized as the total duration (in milliseconds) that the eyes remained fixated within the ROI during image presentation. Values were averaged across all NSSI-related cue images at baseline (Day 0) and post-intervention (Day 8). A clinically relevant improvement in inhibitory control was defined as a ≥20% reduction in total dwell time on NSSI-related cues relative to baseline.

The experiment consisted of 192 trials (64 × 3), preceded by a 20-trial practice phase. Each trial began with a 1.5-second fixation cross, followed by a left- or right-pointing arrow (maximum duration: 2 seconds), to which participants responded as quickly and accurately as possible. In approximately 25% of trials, an auditory stop signal was presented after a variable delay, requiring participants to inhibit their response. The stop-signal delay (SSD) was dynamically adjusted using a staircase procedure (initial delay: 250 ms; ±50 ms based on performance) to index inhibitory control. The inter-trial interval was fixed at 30 seconds.

The study employed a Delay Discounting Task (DDT) to assess individuals' preference for immediate versus delayed rewards. The task included 80 trials, generated by fully crossing four delayed reward amounts (¥25, ¥50, ¥100, ¥500), five delay durations (7, 14, 30, 90, and 180 days), and four discount rates (70%, 85%, 90%, and 95%). Each trial began with a 1.5-second fixation cross, followed by a simultaneous presentation of two options: a smaller immediate reward and a larger delayed reward, with their positions randomized across trials. Participants selected their preferred option using the left or right arrow keys, and no feedback was provided.、

The Hamilton Depression Rating Scale (HAMD) is a clinician-administered questionnaire widely used to assess the severity of depressive symptoms. The 17-item version (HAMD-17) is the most commonly used, with total scores ranging from 0 to 52. Higher scores indicate greater severity of depression

The Hamilton Anxiety Rating Scale (HAMA-14) is a clinician-administered scale assessing the severity of anxiety symptoms. It comprises 14 items, with total scores ranging from 0 to 56. Higher scores indicate greater anxiety severity.

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.

The Ruminative Responses Scale (RRS) is a self-report measure assessing rumination, defined as repetitive and passive thinking about negative emotions and their causes. The 22-item version yields total scores from 22 to 88, with higher scores indicating more frequent rumination.

The Difficulties in Emotion Regulation Scale-Short Form (DERS-16) is a 16-item self-report measure assessing emotion dysregulation across multiple dimensions. It assesses five dimensions: non-acceptance of emotional responses, difficulties engaging in goal-directed behavior, impulse control difficulties, limited access to emotion regulation strategies, and lack of emotional clarity.Total scores range from 16 to 80, with higher scores indicating greater difficulties in emotion.

The Patient Health Questionnaire-9 (PHQ-9) is a 9-item self-report scale assessing depression severity based on DSM-5 criteria. Total scores range from 0 to 27, with higher scores indicating more severe depressive symptoms. Scores ≥10 suggest moderate depression.

The Generalized Anxiety Disorder-7 (GAD-7) is a 7-item self-report screening tool for anxiety symptoms. Total scores range from 0 to 21, with higher scores indicating greater anxiety severity. Scores ≥10 indicate moderate anxiety.