Dwell time and psychological screening outcomes among military service members with multiple combat deployments.

Recent studies have found that longer dwell times, or the period of time between deployments, may be protective against combat-related psychological outcomes. The purpose of this study was to examine the association between dwell time and psychological morbidity, while accounting for combat exposure. U.S. Marines with two combat deployments between 2005 and 2008 were identified from electronic deployment records. Those who screened positive for post-traumatic stress disorder and depression, and who were referred for mental health services were identified from the Post-Deployment Health Assessment. For the final study sample of 3,512 Marines, dwell time was calculated as time between deployments, and was analyzed as a ratio over length of first deployment. After adjustment for all covariates, there was an interaction (p = 0.01) between dwell time and combat exposure on mental health referral outcome. For personnel with maximum reported combat exposure, longer dwell times were associated with a 49% to 92% reduced odds of mental health referral. Longer dwell times may be protective against combat-related psychological outcomes. Because multiple deployments are likely to be the norm in future military operations, regulating dwell time, particularly for those with greater risk of combat exposure, should continue to be explored.