Doctoral student Johannes Eichstaedt of the School of Arts & Sciences says, “We now think of chronic stress as a chronic upregulation of the sympathetic nervous system.”

http://www.washingtonpost.com/local/why-do-nasty-online-comments-get-us-so-riled-up-its-literally-in-our-dna/2015/01/25/49a6bea2-a258-11e4-b146-577832eafcb4_story.html January 25, 2015 The Washington Post