摘要：Objective. We investigated relations between deployment and new-onset depression among US service members recently deployed to the wars in Iraq and Afghanistan. Methods. We included 40 219 Millennium Cohort Study participants who completed baseline and follow-up questionnaires and met inclusion criteria. Participants were identified with depression if they met the Primary Care Evaluation of Mental Disorders Patient Health Questionnaire criteria for depression at follow-up, but not at baseline. Results. Deployed men and women with combat exposures had the highest onset of depression, followed by those not deployed and those deployed without combat exposures. Combat-deployed men and women were at increased risk for new-onset depression compared with nondeployed men and women (men: adjusted odds ratio [AOR] = 1.32; 95% confidence interval [CI] = 1.13, 1.54; women: AOR = 2.13; 95% CI = 1.70, 2.65). Conversely, deployment without combat exposures led to decreased risk for new-onset depression compared with those who did not deploy (men: AOR = 0.66; 95% CI = 0.53, 0.83; women: AOR = 0.65; 95% CI = 0.47, 0.89). Conclusions. Deployment with combat exposures is a risk factor for new-onset depression among US service members. Post-deployment screening may be beneficial for US service members exposed to combat. Depression is one of the most prevalent and costly of all public health problems. 1 , 2 Estimates of the 12-month and lifetime prevalence for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition ( DSM-IV ) 3 major depressive disorders is 5.3% to 6.6% and 13.2% to 16.2%, respectively. 4 , 5 Much of the burden associated with depression results from comorbidities and reduced ability to maintain employment. Estimates predict that by 2020 depression will be second only to ischemic heart disease as a cause of disability. 6 Even those with minor depression have higher levels of impairment based on measures of functional status and social health, and incur higher rates of medical services utilization. 7 Female gender and heredity are reported risk factors for depression. 4 , 8 Women are twice as likely to be diagnosed with depression as men, which may be the result of differences in biological vulnerabilities and environmental experiences. 9 Individuals experiencing threats to personal safety, such as living in unsafe neighborhoods, and individuals living close to the World Trade Center following the events of September 11, 2001, were found to be at increased risk for depression. 10 , 11 Deployments pose unique and often stressful situations to military personnel. Although the association between deployment and posttraumatic stress disorder (PTSD) has been investigated, 12 – 20 little is known regarding the risk for depression. One cross-sectional survey that utilized previously studied UK veterans at high risk for mental disorders found depression more common than posttraumatic stress disorder. 21 Another cross-sectional study utilizing National Comorbidity Survey data found an increased risk for major depressive disorders among male participants with combat experience. 22 These findings are supported by other population-based studies that observed an increased risk for mental disorders among 1991 Gulf War veterans, 23 , 24 and 1991 Gulf War or Bosnia veterans 25 ; however, none were of longitudinal design. More recently, members of the US Army and US Marine Corps were at increased risk for depression upon return from combat duties in Afghanistan and Iraq, compared with soldiers who completed questionnaires within 1 week prior to deployment. 13 However, questionnaires were administered anonymously, making it difficult to identify new-onset depression upon return from deployment. Similarly, a cross-sectional survey of Canadian Forces identified significant associations between depression and exposure to combat or atrocities. 26 Finally, depression following deployment may be comorbid with PTSD 27 and other mental disorders. 25 Per Department of Defense policy, all members are screened for mental disorders before deployment. 28 , 29 Screening includes a review of medical records and an interview with a credentialed provider. Diagnosis or symptoms of depression and PTSD must be assessed for deployment suitability. Disqualifying mental health conditions include, among others, bipolar disorder and psychotic disorders, and disqualifying medications include, but are not limited to, lithium, antipsychotics, and anticonvulsants. Also, those with changes in mental disorder treatment with less than 3 months of stability, or other concerns regarding fitness for duty while deployed, are disqualified. The Millennium Cohort is the largest-ever population-based prospective study of a military population designed to improve the scientific knowledge of the long-term health effects associated with military service. 30 Between 2001 and 2008, 3 panels of US service members were enrolled into the study. Baseline enrollment for the 3 panels ended with 31% of those invited consenting to participate in the 21-year study. The first enrollment cycle was conducted between July 2001 and June 2003, with more than 77 000 individuals completing either a postal or Internet questionnaire. Between 2004 and 2006, approximately 71% of the first panel members completed a follow-up questionnaire. Investigations of potential reporting biases showed no differential in health care utilization in the year prior to enrollment 31 ; strong test–retest reliability 32 ; reliable reporting of vaccinations, 33 , 34 occupations, 35 and deployments 36 ; and minimal differences between participants choosing submission by Internet survey or paper submission. 37 Analyses of potential responder bias in ongoing follow-ups continue. The Millennium Cohort questionnaire includes, among other questions, mental health measures based on 2 standardized scoring instruments: the Primary Care Evaluation of Mental Disorders Patient Health Questionnaire (PHQ) 38 and the Medical Outcomes Study Short Form 36-Item Health Survey for Veterans. 39 We used Millennium Cohort Study data to investigate the association of new-onset depression and deployment in support of the wars in Iraq and Afghanistan.
