This trial is a single-center, single-blind, randomized, sham-stimulation controlled clinical trial. The primary objective of the trial is to detect the targeted effect of tTIS on the nucleus accumbens of adolescent depression patients using functional magnetic resonance imaging (MRI). The secondary objective is to evaluate the potential therapeutic efficacy of TIS treatment for adolescent MDD by assessing changes in clinical characteristics of participants, electrophysiological outcomes, and providing feasibility and tolerance estimates for large-scale efficacy trials. Thirty adolescent MDD participants aged 13 to 17 will be recruited and randomly assigned to receive 10 TIS treatments or sham stimulation treatments (15 participants per group). The trial includes pre-treatment and post-treatment MRI brain scans, clinical assessments, and resting-state EEG, fNIRS acquisition. Follow-ups will be conducted at baseline, after the 10th day of treatment, at the 4th week, and the 8th week. The Montgomery-Åsberg Depression Rating Scale (MADRS), the 17-item Hamilton Depression Rating Scale (HAMD-17), and the Self-Rating Depression Scale (SDS) will be used to assess changes in depressive symptoms of the subjects. The Hamilton Anxiety Rating Scale (HAMA) and the Self-Rating Anxiety Scale (SAS) will be used to assess anxiety symptoms of the subjects. The Wechsler Adult Intelligence Scale-Revised China (WAIS-RC) will be used to assess cognitive function of the subjects.

Inclusion Criteria:

• 1) Age 13 - 17 years old; 2)Meet the DSM-5 criteria for MDD with a current MDE without psychotic features, as confirmed by the MINI 3) HAMD-17 total score of ≥20 4) No change in treatment regimen in the 4 weeks prior to screening 5) No severe mental disorders or intellectual disabilities; 6)Can cooperate actively with the experimental process and subsequent follow-up.

Exclusion Criteria:

• 1) serious diseases such as heart, liver, kidney and hematopoietic system disorders; 2) abuse drugs or are addicted to alcohol or suffer from uncontrollable mental illnesses; 3) Active suicidal intent, confirmed by the MINI Module B (Suicidality) or HAMD-17 item #3 score ≥3; 4) Pregnant or lactating; 5) Those who have identified definite organic lesions such as infarction foci, softening foci, hemorrhage foci, and space-occupying lesions through plain scan of cranial MRI; 6) Those with implanted objects in the brain (such as aneurysm clips, shunt devices, stimulators, cochlear implants or electrodes) or any other metal objects in or near the head, and cannot be safely removed; 7) Change in medication or psychotherapy treatment regimen before screening 8) Could not cooperate with fMRI examination or tTIS treatment; 9)Have received other forms of brain stimulation treatment in the past 3 months.