Traditional mental health studies rely on information
primarily collected through personal contact with a
health care professional. Recent work has shown the
utility of social media data for studying depression,
but there have been limited evaluations of other men-
tal health conditions. We consider post traumatic stress
disorder (PTSD), a serious condition that affects mil-
lions worldwide, with especially high rates in military
veterans. We also present a novel method to obtain a
PTSD classifier for social media using simple searches
of available Twitter data, a significant reduction in train-
ing data cost compared to previous work. We demon-
strate its utility by examining differences in language
use between PTSD and random individuals, building
classifiers to separate these two groups and by detect-
ing elevated rates of PTSD at and around U.S. military
bases using our classifiers.