In April 2003, one month after the ground war began in Iraq, the US Department of Defense mandated that all service members be required to complete a brief Post-Deployment Health Assessment (PDHA) immediately upon return from any deployment using revised Department of Defense Form 2796.11 The purpose of this screening is to review each service member's current health, including mental health or psychosocial issues, possible deployment-related exposures, and to discuss deployment-related health concerns. The PDHA instrument consists of 3 pages of self-administered questions pertaining to deployment location, general health, physical symptoms, mental health concerns, and exposure concerns.11 About a half a page is devoted to questions related to mental health concerns, including posttraumatic stress disorder symptoms, depression, suicidal ideation, aggression, and interest in receiving mental health services. The forms are completed either electronically using handheld devices or on paper surveys immediately before leaving country or within 1 to 2 weeks of returning home. All service members who complete the PDHA instrument are interviewed immediately by a credentialed health care professional (physician, nurse practitioner, or physician assistant) who makes a determination about whether referral for further evaluation is required. The PDHA form presents prompts to help the professional document concerns and referral needs and discuss resources to resolve postdeployment issues.11 Mental health services are available on site to handle immediate referrals (such as for suicidal ideation); most referrals are nonurgent and are scheduled after the service member returns to his/her home base. The completed original PDHA is maintained in the individual's permanent medical record, and a copy is sent to the Army Medical Surveillance Activity for integration into the Defense Medical Surveillance System (DMSS) database. The DMSS, the source of data for this study, is an integrated public health surveillance database that includes data on all health care visits among military personnel, as well as demographic data (eg, age, sex) and service-related data (ie, date of entry into service, date of separation from service, rank, service component, occupation, and deployment history)