Investigating the Psychological and Physiological Effects of Igusa (Juncus effusus L. var. decipiens “Suzukaze”) Scent： A Pilot Study Using Igusa Water

Abstract

Background Tatami mats, an integral part of traditional Japanese architecture, are renowned for their distinctive scent primarily derived from rush (Juncus effusus L. var. decipiens) or igusa in Japanese. Although the aroma of tatami is deeply ingrained in Japanese culture, its potential psychological and physiological effects remain underexplored. Methods This study investigated the effects of igusa scent on mood, cognitive function, and behavior. The experiment was conducted in three stages to clarify its effects; 1. on brain activity when individuals inhaled a scent released from an inhaler in a small closed room, 2. on healthy subjects’ moods in a normal living environment with a scent emitted by a diffuser, and 3. on the well-being of elderly individuals in a normal living environment using scents emitted by a diffuser. EEG monitor, visual stimuli tests, POMS mood test, 100 square calculation tests, and questionnaire were used for healthy individuals. MMSE test, DBD test, and CMAI test were used for individuals with dementia. Results Subsequent experiments involving healthy individuals and elderly participants in nursing homes revealed that igusa scent enhanced cognitive function, improved mood, and reduced behavioral symptoms, especially among elderly individuals with dementia. Conclusions The scent of igusa water demonstrated its effects regardless of preference. It can also be expected to have an effect through long-term exposure, even for those who do not perceive the scent.