Oral Thiamine (Vitamin B1) for Depression in Children and Adolescents

This will be a 28-day, open-label, Phase 2a pilot trial to evaluate the efficacy and safety of 100 mg of daily oral thiamine in the treatment of depression in children and adolescents. Subjects will include pediatric patients 8-17 years of age with elevated depressive symptoms. The investigators plan to enroll 40 subjects to account for an expected dropout rate, with the goal of retaining 30 participants for analysis. The main outcome measures will be improvement in depressive symptoms as measured by the Children Depression Rating Scale-Revised (CDRS-R). Overall clinical functioning will be assessed using the Clinical Global Impression of Severity (CGI-S) and Improvement (CGI-I) scales. The Children's Depression Inventory-2 Parent Form (CDI-2) will also be included as a secondary outcome measure. Thiamine status will be assessed by measuring thiamine diphosphate (TDP) concentrations in whole blood samples (3 mL), collected in EDTA tubes (lavender top) at two time points: at baseline and at the end of study (Day 28). In addition to measuring thiamine diphosphate (TDP) concentrations, the investigators will also assess a panel of inflammatory and metabolic biomarkers at baseline and at the end of study (Day 28). These biomarkers include C-reactive protein (CRP), tumor-necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and leptin. Biomarker testing allows exploration of potential thiamine mechanisms of action. The investigators plan to treat subjects with the following doses: Thiamine hydrochloride (HCL): 100 mg daily At each visit, measures of safety and efficacy will be obtained using rating scales.