Selenium Supplementation for Improving Depression in Children and Adolescents: Efficacy and Mechanistic Study

This randomized, double-blind, placebo-controlled trial will evaluate the efficacy and safety of selenium supplementation (selenium yeast) combined with fluoxetine in children and adolescents with major depressive disorder (MDD). Eligible participants are aged [specific age range if applicable], meet DSM-5 criteria for a current depressive episode, and have a CDRS-R score ≥40 confirmed by trained psychiatrists. A total of [planned sample size] participants will be randomized 1:1 to receive either fluoxetine plus selenium yeast or fluoxetine plus placebo. Selenium yeast will be administered at 60-200 μg/day. Fluoxetine will begin at 10 mg/day and may be adjusted by the treating psychiatrist within a range of 20-60 mg/day. The placebo consists of commercially available yeast tablets identical in appearance, taste, and size to selenium yeast, administered at 60-200 μg/day. Biological samples (blood, urine, stool) will be collected for routine laboratory tests, thyroid, liver, and kidney function, and serum will be analyzed for selenium and ferroptosis-related biomarkers. Brain MRI will also be performed. These assessments will be repeated at weeks 4 and 8 of treatment, together with rating scale evaluations and biospecimen collection. The primary outcome is the change in depressive symptoms, measured by the CDRS-R and Beck Depression Inventory (BDI). Secondary outcomes include anxiety symptoms (SCARED, HAMA), overall clinical improvement (CGI-S, CGI-I), manic symptoms (YMRS), suicide risk (C-SSRS), quality of life (PedsQL 4.0), sleep quality (PSQI), and rumination (RSS). Safety will be monitored through adverse events, vital signs, laboratory tests, and tolerability assessments. This study will provide preliminary evidence on the adjunctive role of selenium supplementation in fluoxetine treatment for adolescent depression and inform future large-scale trials.

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.