Issue Navigator

Volume 15 No. 08
Earn CME
Accepted Papers

Scientific Investigations

Effect of Yokukansan for the Treatment of Idiopathic Rapid Eye Movement Sleep Behavior Disorder: A Retrospective Analysis of Consecutive Patients

Kentaro Matsui, MD1,3; Taeko Sasai-Sakuma, PhD2,4,5; Jun Ishigooka, MD, PhD6; Katsuji Nishimura, MD, PhD1; Yuichi Inoue, MD, PhD2,3
1Department of Psychiatry, Tokyo Women’s Medical University, Tokyo, Japan;; 2Department of Somnology, Tokyo Medical University, Tokyo, Japan;; 3Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan;; 4Department of Life Sciences and Bio-informatics, Division of Biomedical Laboratory Sciences, Graduate School of Health Sciences, Tokyo Medical and Dental University, Tokyo, Japan;; 5Department of Clinical Laboratory Science, Faculty of Medical Technology, Teikyo University;; 6Institute of CNS Pharmacology, Kanagawa, Japan

Study Objectives:

The herbal medicine Yokukansan (YKS; Yi-Gan San in Chinese) is reported to be effective for treating rapid eye movement sleep behavior disorder (RBD). However, the effectiveness and safety of YKS treatment have not been confirmed in a large sample. Thus, we retrospectively analyzed the outcomes of YKS treatment on patients with RBD using clinical records.


Treatment outcomes were evaluated using the Clinical Global Impression of Illness Severity (CGI-S) and Improvement (CGI-I) scales. Patients with scores of 1 (very much improved) and 2 (much improved) on the CGI-I were classified as responders. After excluding patients with very mild RBD symptoms and those without detailed clinical information, 36 patients with idiopathic RBD including 17 receiving YKS monotherapy and 19 receiving YKS add-on therapy in addition to other medication were analyzed.


The patients’ mean age [standard deviation, SD] was 69.3 [6.8] years, and the mean duration of RBD morbidity [SD] was 5.7 [3.5] years at the start of YKS treatment. Importantly, 12 of 17 patients (70.6%) receiving YKS monotherapy were responders. However, among patients receiving YKS add-on therapy, the proportion of responders was substantially lower (4 of 19 patients; 21.1%). No adverse events were reported, other than mild gastric distress in one case.


Considering the effectiveness of YKS and the low likelihood of adverse events, YKS should be considered as a potential treatment for patients with RBD.


Matsui K, Sasai-Sakuma T, Ishigooka J, Nishimura K, Inoue Y. Effect of yokukansan for the treatment of idiopathic rapid eye movement sleep behavior disorder: a retrospective analysis of consecutive patients. J Clin Sleep Med. 2019;15(8):1173–1178.

Please login to continue reading the full article

Subscribers to JCSM get full access to current and past issues of the JCSM.

Login to JCSM

Not a subscriber?

Join the American Academy of Sleep Medicine and receive a subscription to JCSM with your membership

Subscribe to JCSM:  $125/volume year for individuals or $225/volume year for institutions to access all current articles and archives published in JCSM.

Download this article*:   $20 to access a PDF version of a specific article from the current issue of JCSM.

*Purchase of an article provides permission to access and print the article for personal scholarly, research and educational use. Please note: access to the article is from the computer on which the article is purchased ONLY. Purchase of the article does not permit distribution, electronic or otherwise, of the article without the written permission of the AASM. Further, purchase does not permit the posting of article text on an online forum or website.