Mitochondria play a crucial role in neuronal function, especially in energy production, generation of reactive oxygen species, and calcium signaling. Multiple lines of evidence have suggested possible involvement of mitochondrial deficits in major psychiatric disorders, such as schizophrenia and bipolar disorder. In the first half, this review will outline the current understanding of the physiological role of mitochondria and their dysfunction under pathological conditions, particularly in psychiatric disorders. Nevertheless, the current knowledge about mitochondrial deficits in these disorders is somewhat limited, due to the lack of effective methods to dissect dynamic changes in the functional deficits that are directly associated with psychiatric conditions. Human neuronal cell model systems, which have been dramatically developed in recent years through the use of stem cell technology, may be key tools for overcoming this dilemma and improving our understanding of the dynamic changes in the mitochondrial deficits in patients with psychiatric disorders. We introduce recent discoveries from new experimental models and conclude the discussion by referring to future perspectives. In the perspectives, we emphasize the significance of combining studies of human neuronal cell models with those of other experimental systems, including animal models.
