An object of the present invention is to develop a method of enhancing the cognitive ability of a brain to fundamentally cure a disease. It has been found out that, by using a medicament for treating or preventing a disease including a combination of a major tranquilizer, and vitamin C or a salt thereof and, if necessary, drip infusion, an antidepressant and an iron agent, the cognitive ability of a brain is enhanced, thus, an arbitrary disease including various cancers can be treated. The present invention also provides a method for treating or preventing a disease including a step of administering a major tranquilizer, and vitamin C or a salt thereof to a subject suffering from the disease.
