Gallbladder meridian(GB) acupoints may play an important role in the treatment of major depressive disorder (MDD). Therefore, this study is designed to focus on the traditional Chinese medicine (TCM) theory of " gallbladder dominating decision ", take the GB as the entry point, and use functional Near-Infrared Spectroscopy(fNIRS) technology to observe the effect of intradermal acupuncture on the cerebral hemodynamic indexes of the prefrontal cortex and bilateral temporal cortex of patients with MDD.

This study will include 20 patients with MDD (observation group) and 20 healthy control participants without MDD (control group). fNIRS will be adopted to assess regional oxygen saturation of the blood in the MDD-related cerebral cortex: the prefrontal and bilateral temporal cortex. Based on the results of the fNIRS, to explore cerebral hemodynamic changes in the prefrontal and bilateral temporal cortex in patients with MDD. By observing the changes of hemodynamic characteristics of the prefrontal cortex and bilateral temporal cortex of the observation group and the control group during the course of intradermal acupuncture, explore the immediate response of the hemodynamic characteristics of the prefrontal cortex and bilateral temporal cortex of the observation group to the intervention of the GB acupoints.

Inclusion Criteria:

Inclusion criteria for control group:

1. Healthy control participants who could provide a recent depression screening report, and confirm they have not any cardiovascular, respiratory, digestive, urinary, hematological, endocrine, or neurological disease;
2. 15 ≤ age ≤22 years, male or female;
3. Participants have clear consciousness and could communicate with others normally;
4. Participants could understand the full study protocol and have high adherence. Written informed consent is signed by adult participants themselves，and the minor participants is signed by a guardian;
5. Participants should be right-handed;

Inclusion criteria for observation group:

1. MDD patients should meet the diagnostic criteria of the International Classification of Diseases 11th Edition (ICD-11) diagnostic criteria for MDD;
2. 15≤ age ≤22, male or female;
3. Participants have clear consciousness and could communicate with others normally;
4. Participants could understand the full study protocol and have high adherence. Written informed consent is signed by adult participants themselves，and the minor participants is signed by a guardian;
5. Not taking antidepressants or antipsychotic drugs for at least 4 weeks before enrollment;
6. Participants should be right-handed;

Exclusion Criteria:

Exclusion criteria for control group:

1. Participants with serious primary diseases of cardiovascular diseases, liver diseases, kidney diseases, urinary diseases, and hematological diseases;
2. Participants have an illness, alcohol dependence, or a history of drug abuse;
3. Pregnant or lactating participants;
4. Participants with intellectual disabilities who can't cooperate with the questionnaire survey;
5. Participants with bleeding tendency, skin disease, allergic constitution, and allergic to adhesive tape;
6. The test site of participants has scars, hyperpigmentation, red and swollen;
7. Participants are participating in other trials;

Exclusion criteria for observation group:

1. Participants with serious primary diseases of cardiovascular, respiratory, digestive, urinary, hematological, endocrine, neurological disease, and other serious primary diseases, and the disease cannot be effectively controlled clinically;
2. MDD caused by organic mental disorders, schizophrenia, bipolar disorder, psychoactive substances, and non-addictive substances;
3. Participants with suicidal tendencies;
4. Pregnant or lactating participants;
5. Participants with intellectual disabilities who cannot cooperate with the questionnaire survey;
6. Participants with bleeding tendency, skin disease, allergic constitution, and allergic to adhesive tape;
7. The skin at the test site of participants has scars, hyperpigmentation, red and swollen;
8. Participants are participating in other trials;