This cohort study involves the dynamic collection of clinical information from adolescent patients with major depressive episodes (including both major depressive disorder and bipolar disorder), encompassing serum parameters, physiological-behavioral signals, neuroimaging data, and neuropsychological scales. The study aims to summarize the comprehensive clinical characteristics of this population, identify new risk factors, and establish multivariate predictive models for treatment response, cognitive and emotional impairments. Furthermore, this research will thoroughly investigate the underlying neural mechanisms linking clinical manifestations and neuroimaging features in major depressive episodes.