An object of the present invention is to provide a novel composition that is, for example, effective in suppression of deterioration of mental function. The present invention provides a composition for use in suppressing deterioration of mental function, comprising a hop oxidation-reaction product. Conditions of deterioration of mental function include conditions selected from the group consisting of depression-related conditions and anxiety-related conditions. The composition of the present invention can be provided in the form of a food composition, and be ingested by subjects with deterioration of mental function or with a risk of deterioration of mental function. The S-fraction can be used as the hop oxidation-reaction product.