Clinical Research Directory

Inclusion Criteria: * Aged 12-18 years; * Diagnosed with major depressive disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), using the K-SADS-PL diagnostic tool; * A score of ≥28 on the Children's Depression Rating Scale-Revised (CDRS-R); * Adequate visual and auditory abilities to complete the study; * Willingness to participate in the study with informed consent signed by both the participant and a legal guardian. Exclusion Criteria: * Patients with severe psychiatric disorders such as bipolar disorder, schizophrenia, bulimia nervosa, anorexia nervosa, or primary obsessive-compulsive disorder; * Those with severe physical illnesses or other life-threatening conditions; patients in a current depressive episode with a clear suicidal plan or history of suicide attempt; * Individuals with a history of substance or drug abuse; * Those requiring immediate hospitalization for psychiatric disorders; * Patients currently taking medications contraindicated with the investigational drug or that may interfere with its efficacy; * Those who have received modified electroconvulsive therapy (MECT) within the past 12 months; * Individuals allergic to selenium yeast protein, including those with allergic rhinitis, gastrointestinal sensitivity, allergic constitution, or autoimmune diseases such as Graves' disease or Hashimoto's thyroiditis; * Patients with contraindications to magnetic resonance imaging (MRI); * Aand left-handed individuals.