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 mental
health conditions. We consider post traumatic stress
disorder (PTSD), a serious condition that affects millions
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 training
data cost compared to previous work. We demonstrate
its utility by examining differences in language
use between PTSD and random individuals, building
classifiers to separate these two groups and by detecting
elevated rates of PTSD at and around U.S. military
bases using our classifiers.