1. Ekman, P.: Basic Emotions. In: Dalgleish, T., Power, M. (eds.) Handbook of Cognition and Emotion, pp. 45–60. New York, Wiley (1999)
2. May, R.: The Meaning of Anxiety. Ronald Press Co, New York (1950)
3. Kaiya, H., Tsuchida, H., Suyama, H., Kaneko, Y.: Recent advances in the studies of anxiety disorders—an overview. Anxiety Disord. Res. 4(1), 20–36 (2013)
4. Ministry of Health: Labour and Welfare, Summary of 2014 Patient Surveys.
http://www.mhlw.go.jp/toukei/saikin/hw/kanja/14/index.html
. Accessed 10 Feb 2016 (in Japanese)
5. Cabinet Office: National Opinion on People’s Life.
http://survey.gov-online.go.jp/h26/h26-life/index.html
. Accessed 14 July 2016 (in Japanese)