Corresponding Author

International Institute for Integrative Sleep Medicine, University of Tsukuba, Ibaraki, Japan

Ibaraki Prefectural Medical Center of Psychiatry, Ibaraki, Japan

Correspondence: T. Kanbayashi, International Institute for Integrative Sleep Medicine, University of Tsukuba, 1–1-1-Tennodai, Tsukuba, Ibaraki, 305–8575, Japan Tel.: +81–29–853–5857; Email: kanbayashi.ta.fn@u.tsukuba.ac.jp