Schizophrenia onset in the developmental age has a strong neurodevelopmental burden and is associated with a poorer prognosis. The approach to diagnosis is still based on symptomatic description without objective validation. In this study, we aimed to compare the peripheral blood levels of hypothesized biomarker proteins: brain-derived neurotrophic factor (BDNF), proBDNF, p75 neurotrophin receptor (p75NTR) and S100B between early-onset schizophrenia-spectrum adolescents (n = 45) and healthy controls (n = 34). To read the full article, choose Open Athens “Institutional Login” and search for “Midlands Partnership”.