Bipolar disorder is a major mental disorder characterized by recurring episodes of mania and depression. The cause is unknown, and there are no objective diagnostic tests. Previous studies have suggested that a decrease or hyperexcitability of excitatory neurons of the paraventricular thalamic nucleus may be involved in the pathogenesis of bipolar disorder. In this study, we aim to analyze the pathophysiology of the paraventricular thalamic nucleus using patient-derived iPS cells and mouse models, with the goal of developing diagnostic methods and treatment strategies.