ObjectiveTo evaluate the clinical efficacy of acupuncture in the treatment of adolescent depression and to explore its potential mechanisms based on functional magnetic resonance imaging （fMRI） and serum proteomics. MethodsA randomized， double-blind， sham acupuncture-controlled trial design was conducted. A total of 100 adolescents with depression were enrolled and randomly assigned to an acupuncture group and a sham acupuncture group， with 50 participants in each group. In addition， 20 healthy subjects were recruited as healthy controls. Participants in the acupuncture group received acupuncture at Baihui （GV 20）， Yintang （GV 29）， Zhongwan （CV 12）， Qihai （CV 6）， bilateral Tianshu （ST 25）， bilateral Neiguan （PC 6）， bilateral Zusanli （ST 36）， and bilateral Taichong （LR3）. The sham acupuncture group received intervention using a blunt placebo needle without skin penetration. Both groups received 30-min treatments three times per week for 4 weeks. The primary outcome was the reduction rate of the 24-item Hamilton Depression Rating Scale （HAMD-24） score. Secondary outcomes included changes in HAMD-24 scores before and after treatment， covering nine factors （anxiety/somatization， cognitive impairment， sleep disturbance， psychomotor retardation， hopelessness， fatigue， weight change， diurnal mood variation， and suicidal ideation）， response rate and remission rate after treatment， and symptom severity before and after treatment. Subgroup analyses of total HAMD-24 scores were performed according to concomitant medication use and the number of medications taken. During the study period， all adverse events were monitored and recorded to evaluate safety. Patients who volunteered and met the eligibility criteria for imaging examinations were selected to undergo brain fMRI scanning and serum proteomic analysis to investigate changes in functional connectivity among brain regions and differential proteins. ResultsA total of 49 participants in the acupuncture group and 50 participants in the sham acupuncture group were included in the efficacy analysis. Among them， 20 participants in the acupuncture group and 21 in the sham acupuncture group completed fMRI scans， while 19 participants in the acupuncture group and 21 in the sham acupuncture group completed serum proteomic analyses. After 4 weeks of treatment， the mean reduction rate of HAMD-24 score in the acupuncture group was significantly higher than that in the sham acupuncture group ［（58±24）% vs.（26±19）%， P＜0.01］. Compared to baseline， scores for anxiety/somatization， cognitive impairment， psychomotor retardation， and hopelessness， and the total HAMD-24 score significantly decreased in both groups. In addition， the acupuncture group showed significant reductions in sleep disturbance， fatigue， and suicidal ideation scores （P＜0.01）. After treatment， the response rate and remission rate were 67.35% （33/49） and 24.48% （12/49） in the acupuncture group， respectively， significantly higher than 6.00% （3/50） and 0 in the sham acupuncture group （P＜0.01）. The proportion of participants with moderate symptoms was lower， whereas the proportion with mild symptoms was higher in the acupuncture group than the sham acupuncture group （P＜0.01）. Among those receiving acupuncture alone， acupuncture combined with medication， or fewer than three medications， the total HAMD-24 scores decreased after treatment in both the acupuncture subgroup and the sham acupuncture subgroup， with significantly lower scores in the acupuncture subgroup （P＜0.01）. During the study period， four mild adverse events were reported， including one case in the acupuncture group and three cases in the sham acupuncture group； none of these events affected the continuation of treatment. fMRI results showed that acupuncture enhanced functional connectivity between the prefrontal cortex and cerebellar-limbic system-related brain regions. Proteomic analysis identified 24 differentially expressed proteins associated with acupuncture treatment， mainly enriched in pathways related to neuroinflammation and energy metabolism. ConclusionAcupuncture can significantly improve depressive symptoms in adolescents with depression. Its therapeutic effects may be achieved by modulating emotion-related brain networks and regulating pathways associated with neuroinflammation and energy metabolism.