Research suggests a correlation between those that suffer from PTSD and chronic pain. You mean it can all be related? Below is the abstract and link to the article. It is somewhat of a dry read but in a nutshell suggests a strong correlation between the two.
Cho SK, Heiby EM, McCracken LM, Moon DE, Lee JH. Daily Functioning in Chronic Pain: Study of Structural Relations with Posttraumatic Stress Disorder Symptoms, Pain Intensity, and Pain Avoidance. Korean J Pain. 2011 Mar;24(1):13-21. doi: 10.3344/kjp.2011.24.1.13