Author(s)： Takaaki Kubo, Tomonori Yasuda, Yoshihisa Masumitsu, Yoshihiro Iwashita, Satoshi Watanabe, Taichi Ishizawa, Mitsuo Tsunakawa, Shingo Yano, Junichi Iimaya
Frequent bathtub bathing (BB) improves the mental health of middle-aged and older Japanese in-dividuals. This study investigated the chronic mental health effects of BB, maintaining warmth using an insulating sheet and sleeping bag after bathtub bathing (BBW), and bathtub bathing with herbal extracts (BBH) in healthy young adults. The study involved healthy young adults who habitually showered, as opposed to bathing. In the first experiment, 18 participants were randomly assigned to either the BB or BBW groups for 14 consecutive nights. After a 2-week washout period, the participants were asked to switch their bathing styles (a cross-over design). In the second experiment, 20 participants were randomly assigned to the BB or BBH group. The herbal extracts for the BBH group contained angelicae radix, aurantii nobilis pericarpium, chamomile, and zingiberis rhizoma. After a 2-week washout period, these participants also switched to the other bathing style. The participants’ mental conditions pre- and post-intervention were assessed using the Profile of Mood States-Brief Form questionnaire, Japanese version, and were statistically analyzed. The participants’ Anger-Hostility score converged to an average (50 points) in the post-BBW and post-BBH participants, and there were no significant differences in BB. The Confusion change rate was significantly different in the first experiment (BB versus BBW). The Depression-Dejection and Fatigue change rates were significantly different in the second experiment (BB versus BBH). Our findings suggest that changing bathing style from showering to BBW or BBH improves the POMS Anger-Hostility scores of healthy young adults.