[Problem to be solved]Provision of an agent for preventing or treating a functional brain disease and/or inhibiting symptom development of the same.[Means for solving the problems]An agent for preventing or treating a functional brain disease and/or inhibiting symptom development of the same, which comprises (2R)-2-propyloctanoic acid or a salt thereof.The agent for preventing or treating a functional brain disease and/or inhibiting symptom development of the same, which comprises (2R)-2-propyloctanoic acid or a salt thereof, can be safely administered to patients of, for example, functional brain diseases such as depression, menopausal mood disorder, perimenopausal mood disorder, panic disorder, irritable bowel syndrome, social anxiety disorder, post-traumatic stress disorder or the like, and also can show excellent effects.
