Participants in the acupuncture group will receive real acupuncture treatment. Acupoints will be selected according to the Chinese national standard "Nomenclature and Location of Meridian Points" (GB/T 12346-2006), including Baihui (GV20), Sishencong (EX-HN1), Shenting (GV24), Touwei (ST8), Fengchi (GB20), Anmian (EX-HN22), Neiguan (PC6), Shenmen (HT7), and Sanyinjiao (SP6). Electrical stimulation will be applied using sparse-dense waves at frequencies of 2 Hz and 100 Hz, with an intensity ranging from 0.1 to 1 mA. Treatment will be performed by licensed acupuncturists following a standardized operation manual. Each acupuncture session lasts 30 minutes, and participants will receive one session of acupuncture treatment. Participants will remain blinded to group allocation.

Participants in the sham acupuncture group will receive sham acupuncture using non-insertive placebo needles. The same acupoints and treatment protocol will be applied as in the acupuncture group (sham acupuncture session lasting 30 minutes, single session). The procedure mimics real acupuncture without skin penetration or active stimulation, and appears visually indistinguishable from real acupuncture. The electroacupuncture device will not deliver electrical output. Participants will remain blinded to group allocation.

Participants will receive standardized acupuncture treatment for mild to moderate depression according to the study protocol. Acupuncture will be administered by qualified practitioners at predefined acupoints during the treatment period.

Change in short-term depressive symptom severity measured by the Montgomery-Åsberg Depression Rating Scale (MADRS), a 10-item scale with a total score ranging from 0 to 60. Higher scores indicate worse depression outcomes.

Change in short-term depressive symptom severity measured by the 17-item Hamilton Depression Rating Scale (HAMD-17). The total score ranges from 0 to 52, with higher scores indicating more severe depression.