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 12-18 years, meet DSM-5 criteria for a current depressive episode, and have a CDRS-R score ≥40 confirmed by trained psychiatrists. A total of 172 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-II (BDI-II). 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 (RRS). 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.