摘要：Objective. We investigated the association of the length of time spent at home between deployments, or dwell time, with posttraumatic stress disorder (PTSD) and other mental health disorders. Methods. We included US Marine Corps personnel identified from military deployment records who deployed to Operation Iraqi Freedom once (n = 49 328) or twice (n = 16 376). New-onset mental health diagnoses from military medical databases were included. We calculated the ratio of dwell-to-deployment time (DDR) as the length of time between deployments divided by the length of the first deployment. Results. Marines with 2 deployments had higher rates of PTSD than did those with 1 deployment (2.1% versus 1.2%; P < .001). A DDR representing longer dwell times at home relative to first deployment length was associated with reduced odds of PTSD (odds ratio [OR] = 0.47; 95% confidence interval [CI] = 0.32, 0.70), PTSD with other mental health disorder (OR = 0.56; 95% CI = 0.33, 0.94), and other mental health disorders (OR = 0.62; 95% CI = 0.51, 0.75). Conclusions. Longer dwell times may reduce postdeployment risk of PTSD and other mental health disorders. Future research should focus on the role of dwell time in adverse health outcomes. Military deployment has long been recognized as a stressor because it removes individuals from the comfort of home and can strain relationships with spouses and other family members. 1,2 The number of combat deployments increases during times of military conflict, as was the case in the years following the events of September 11, 2001. With the initiation of Operation Enduring Freedom (OEF) in October 2001 and Operation Iraqi Freedom (OIF) in March 2003, the pace of military operations increased markedly and many service members experienced multiple deployments to the combat zone. 3 The cumulative health-related effects of multiple combat deployments are not well understood and are an emerging public health problem. Multiple studies have identified an increase in mental health morbidity following a single deployment. 4–7 Research on the mental health effects of multiple deployments, however, is limited. In 2007, the Mental Health Advisory Team (MHAT) found that soldiers on their third or fourth deployment in support of OIF had a significantly higher risk of mental health and work-related problems than did soldiers on their first or second deployment. 8 Other studies have also identified increases in mental health symptoms, particularly symptoms of posttraumatic stress disorder (PTSD), among personnel preparing for and after their second OIF deployment. 9,10 One study of British military personnel found that a higher prevalence of mental health symptoms was associated with deployment length but not with frequency of deployments. 11 The most recent MHAT report was the first to provide evidence suggesting a protective effect of dwell time (or the period of time at home between deployments) on self-reported adverse mental health symptoms, though actual medical utilization was not examined. 12 Dwell time and multiple deployments have also been the subject of recent media reports. Secretary of Defense Robert Gates and Senator Jim Webb recently called for establishing minimum requirements for time at home between deployments. 13,14 A variety of factors can influence the determination of a service member’s dwell time, including current operational needs and unit rotation schedule. In our study, we aimed to identify new-onset mental health diagnoses among US Marines with 1 and 2 OIF deployments. Among those with 2 OIF deployments, we examined the association of dwell time with PTSD and other mental health disorders. We hypothesized that increased dwell time relative to first deployment length would be associated with lower rates of adverse mental health outcomes.
