Mitochondrial dysfunction has been linked to many psychiatric disorders. Ketogenic diets have been shown to reduce mitochondrial dysfunction and thus may be helpful to patients who suffer from these disorders. In this article, we review the effects of a ketogenic diet in patients with psychiatric disorders such as autism, depression, anxiety, and schizophrenia. Mitochondrial dysfunction, and its reversal by a ketogenic diet resulting in the relief of mental disorders, would be an excellent teaching topic on the consequences of altered cellular biology and a discussion of mitochondrial injury as one of the causes of cellular necrosis. Similarly, this information will be important in a discussion of how diet might be beneficial in the treatment of certain mental disorders.