To investigate the intervention effect of high-definition transcranial alternating current stimulation (HD-tACS) on patients with Non-suicidal Self-injury (NSSI) and its underlying neural mechanism by magnetic resonance imaging (MRI).

Forty patients with Non-suicidal Self-injury (NSSI) diagnosed by DSM-5 were recruited from the Second Affiliated Hospital of Anhui Medical University. All participants underwent a structured interview and routine laboratory examination before and after receiving high-definition transcranial alternating current stimulation (HD-tACS) treatment after meeting the inclusion criteria and obtaining informed consent. Each participant will complete the clinical evaluation, magnetic resonance imaging (MRI), and HD-tACS treatment conducted by trained researchers at the Second Affiliated Hospital of Anhui Medical University. All the participants were randomized (1:1) to receive an "active HD-tACS" or "sham HD-tACS" treatment protocol. tACS: the central electrode was placed over F3 with return electrodes placed at Fp1, Fz, F7 and C3. Fourteen 2-mA sessions (ramp-up and ramp-down periods of 15 and 15 seconds, respectively) were applied for 20 minutes per session, twice daily over 7 consecutive days, and the stimulus frequency was set as individual alpha frequency (IAF). Sham HD-tACS was delivered using the same protocol and current intensity, but the period of active stimulation was only during the ramp-up and ramp-down periods of 15 and 15 seconds.

Before and after the treatments, the patients received a battery measure of neuropsychological tests, and MRI scans in multimodalities. The neuropsychological assessment included the Ottawa Self-injury Inventory (OSI), the Adolescent Non-suicidal Self-injury Assessment Questionnaire (ANSAQ), the Hamilton Depression Rating Scale (HAMD), the Hamilton Anxiety Rating Scale (HAMA), and Patient Health Questionnaire-15 (PHQ-15) etc.Multimodal MRI includes 3D-T1, rs-fMRI, and DTI. The symptoms of the patients were followed up one and two months after the end of treatments.

Inclusion Criteria:

The patients were diagnosed by 2 or more senior clinical psychiatrists, meeting DSM-V criteria, and having 1 or more non-suicidal self-injurious behaviors in the last 6 months.

12-18 years of age.

The medicine has not changed in the 4 weeks prior to or after this study, and if it has to be changed, the treatment medication is required to be at a subtherapeutic dosage level.

Exclusion Criteria:

The patient has suicidal ideation or has committed suicidal behavior

T1 or T2 weighted phase magnetic resonance images show focal brain lesions

patients had neurological disorders such as epilepsy, or serious physical illnesses

patients had a history of substance abuse and drug dependence in the last 6 months or use of anticonvulsant drugs in the last 3 months

patients had received radial cranial electrical stimulation or magnetic stimulation treatment in the last 3 months or received electroconvulsive therapy in the last 6 months

patients had previous significant head trauma or EEG abnormality in the last 1 month

body-mounted devices unsuitable for treatment, such as pacemakers, artificial valves, and other metal implants.