ارتباط غیرمستقیم مبارزه با علائم فیزیکی پس از استقرار در سربازان ایالات متحده: نقش اختلال استرس پس از ضربه، افسردگی و بی خوابی

Objective To characterize the indirect associations of combat exposure with post-deployment physical symptoms through shared associations with post-traumatic stress disorder (PTSD), depression and insomnia symptoms. Methods Surveys were administered to a sample of U.S. soldiers (N = 587) three months after a 15-month deployment to Iraq. A multiple indirect effects model was used to characterize direct and indirect associations between combat exposure and physical symptoms. Results Despite a zero-order correlation between combat exposure and physical symptoms, the multiple indirect effects analysis did not provide evidence of a direct association between these variables. Evidence for a significant indirect association of combat exposure and physical symptoms was observed through PTSD, depression, and insomnia symptoms. In fact, 92% of the total effect of combat exposure on physical symptoms scores was indirect. These findings were evident even after adjusting for the physical injury and relevant demographics. Conclusion This is the first empirical study to suggest that PTSD, depression and insomnia collectively and independently contribute to the association between combat exposure and post-deployment physical symptoms. Limitations, future research directions, and potential policy implications are discussed.

Post-deployment physical symptoms are commonly reported by war veterans [1], [2], [3] and [4]. The prevalence of physical symptoms following combat deployment was intensively studied in the context of reports of ‘Gulf War Syndrome.’ Although no empirical confirmation of a specific syndrome has been identified, studies have consistently revealed associations between Gulf War deployment and physical symptoms spanning multiple health domains. Studies of the most recent conflicts in Iraq and Afghanistan also provide evidence of high rates of mental and physical health problems, with rates of generalized physical health problems considerably higher in service members who have deployed compared with those who have not [1] and [4]. Determining mechanisms by which combat deployment contributes to physical symptoms (independent of physical injury) has proven challenging. The most recent wars have focused attention primarily on concussion/mild traumatic brain injury (mTBI), to which many post-deployment physical symptoms have been attributed. Most studies have failed to support this association, and instead suggest that PTSD and depression are more robust correlates of persistent physical symptoms in service members and veterans with a history of mTBI [5], [6] and [7]. Although there are notable differences in the combat experiences, environmental exposures, operational tempo, and mission characteristics across wars throughout history, it is perhaps telling that each, up to and including the most recent wars in Iraq and Afghanistan, has been associated with similar generalized post-deployment health concerns [2], [3], [4] and [8]. These data collectively suggest that a common set of deployment-related factors contribute to post-combat generalized physical health problems. However, debate has existed after every war as to the relative contribution of physical, psychological, or environmental causes of these post-war health concerns. We hypothesize that mental health conditions are essential considerations for fully explicating the association between combat exposure and physical symptoms. Collectively, PTSD, depression and insomnia are associated with endocrine [9], [10] and [11], inflammatory [12], [13], [14], [15] and [16] and autonomic nervous system [9] and [17] dysregulation, each of which could contribute to general physical health symptoms. The purpose of the present study is to elucidate the relationships among these variables with the aim of determining their role in the development of post-deployment physical symptoms — an important step toward development of optimal treatment strategies. Previous studies suggest that the degree of combat exposure is predictive of post-deployment physical symptomology [2], [4], [18], [19], [20] and [21]. Additional research is needed to more fully characterize the nature of this association. Studies have rarely systematically examined indirect associations of combat exposure and physical symptoms through highly prevalent mental health consequences of combat deployment, and studies that have done so have typically included one mental health indicator, such as PTSD, in the analysis [21]. It is estimated that 6–13% of soldiers who have returned from Iraq or Afghanistan meet criteria for post-traumatic stress disorder (PTSD), and a high rate of major depression disorder has also been documented [22]. Both of these conditions have been strongly correlated with post-deployment physical symptoms (e.g., [3]). Therefore, we hypothesize that the association between combat exposure and physical symptoms is at least in part attributable to variance shared in common with PTSD and/or depression symptoms. Indeed, it has been hypothesized elsewhere that PTSD can account for the effect of prior combat experience on physical health outcomes [21] and [23], and numerous studies have shown that PTSD accounts for greater variance in persistent post-concussive symptoms than mTBI itself (e.g., [7]). Additional research is needed to determine the unique and combined contributions of these factors to the association between combat exposure and post-deployment physical symptoms. Sleep disturbance and insomnia are prevalent in combat theater and in garrison [24], [25] and [26], and have been recognized and highlighted as one of three critical areas of focus for improved soldier health and fitness, as outlined in the Army Surgeon General's ‘Soldier Performance Triad’. To date, sleep has received little consideration as a risk factor for post-deployment physical symptoms. Prior studies examining post-deployment correlates of physical health have characterized and operationally defined sleep disturbance as but one component of the physical symptom milieu [1], [3], [7] and [27]. However, there exists compelling evidence from studies of civilian populations that sleep disturbance might play an important role in the development, maintenance and exacerbation of physical health problems. Sleep disturbance can be triggered and/or exacerbated by stress, and has been linked to physical symptom complaints in a number of field and laboratory studies [28]. Sleep disturbance has also been shown to enhance sensitivity to noxious stimuli in otherwise healthy individuals [29] and [30], and objective polysomnography indicators of sleep disturbance are common among those with chronic pain [31] and [32] and other physical health problems [33], [34] and [35]. In the present study, we hypothesized that PTSD, depression and insomnia symptoms would emerge as important contributory factors to the link between combat exposure and post-deployment physical symptoms. Because insomnia is a phenomenological correlate of PTSD and depression, and may even share some common biological substrates with PTSD and depression [36], [37] and [38], we carefully modeled the relative, or unique, contribution of each of these factors on the combat–physical symptom link. To do so, we utilized a multiple indirect effects model [39] that allowed us to systematically evaluate the direct association of combat exposure with physical symptoms, as well as whether this association was indirect and attributable to variance shared in common with PTSD, depression, and insomnia symptoms (i.e., indirect effects). We examined these associations using an extant dataset from a large cohort of U.S. soldiers following a 15-month deployment to Iraq.

The majority of the soldiers assessed were men (82.4%). Most soldiers (63.8%) were between 18 and 29 years of age, with 29.6% being 30–39 years and 6.6% 40 years or older; 56.1% of the sample was Caucasian; 41.2% had received high school diploma/GED or at least attended some high school, 44% attended some college or possessed an Associate's degree, and 14% had a Bachelor's or graduate degree. The majority of the sample was E1–E4 (53%), with 36% E5–E9 and 10% commissioned officers. These data, and other data derived from LCS surveys, are demographically representative of the infantry population for the Army at-large [22] and [56]. Mean combat exposure was 10.86 combat events (SD = 6.93). The mean PHQ-15 score was 5.34 (SD = 4.36); mean PCL score was 26.19 (SD = 12.53); mean PHQ-9 score was 4.73 (SD = 5.01); and mean ISI score was 7.47 (SD = 6.38). Approximately 10% (n = 66) of the sample reported being wounded or injured during combat. Soldiers who were injured had higher PCL and PHQ-9 scores (p-values < .05). Injury was unrelated to ISI and PHQ-Physical Symptom scores (p-values > .10). Approximately 11% of the sample met self-reported criteria for PTSD; 9.7% for depression; and 15.5% for insomnia.