We briefly summarize two original research papers and a review article. We then review the formal structure of the diagnosis of post-traumatic stress disorder (PTSD) and discuss the use of continuous measures of PTSD in comparison with diagnostic instruments. Problems with distinguishing incident from prevalent PTSD cases lead to questions of whether medical PTSD is a new important problem. By examining current studies, we demonstrate that medical PTSD is lagging in fundamental and interventional research but we discuss how medical PTSD has unique opportunities to develop causal models that could inform the greater field of stress studies. We conclude by advocating that future medical PTSD research efforts should focus on understanding how fundamental brain processes are affected during acute medical stress.