Disease and illness are overlapping, but distinct, constructs. Whereas disease refers to diagnosable physical and psychiatric syndromes, illness refers to the subjective experience of poor health. Illness can manifest itself as bodily symptoms stemming from multiple sources--including psychological, physical, and social agents--and may or may not reflect the presence of an underlying disease. The relationship of illness to disease is complex. A person may experience ill health with no underlying disease. Conversely, individuals may suffer from an underlying disease without regarding themselves as ill.
Perceived stress sets in motion an interrelated set of physiological, behavioral, emotional, and cognitive responses aimed at adapting to environmental demands. Although these responses have adaptive short-term benefits, over time they may act in concert with other host and environmental risk factors to increase the likelihood of poor health.
War-zone deployment is associated with exposure to a spectrum of potentially stressful circumstances, ranging from events such as separation from loved ones to noncombat war-zone events such as harsh living conditions, to combat events such as traditional combat and its often gruesome aftermath. Apart from actual exposure to combat, war-zone deployment is often associated with the perception that oneself or others are at risk of serious injury or loss of life. Although the literature on noncombat exposures associated with war-zone deployment is still emerging, there is increasing recognition that any one of these perceived or actual exposures may contribute to adverse stress reactions. It is not necessary to participate in actual combat to experience stress, nor is it necessary to experience an event of high magnitude.
Although many of the hardships and dangers experienced by veterans of the Gulf War were similar to those experienced by veterans of other wars, this was the first war since WWI in which the clear threat of chemical warfare was known by the troops prior to entering the theater of operations; this was compounded by the combined threats of nuclear and biological weapons. Another difference between the Persian Gulf War and many other previous wars is that U.S. troops in the Gulf experienced low casualty rates. It is possible, albeit speculative, that the greater mortality and more severe morbidity associated with other wars may have drawn attention away from, or obscured recognition of the presence of, psychological or physical symptoms such as those experienced in the Gulf.
The available literature also suggests that stress exposure may act as a contributing risk factor for a range of physical illnesses and disease, including cardiovascular disorders, although the strength of the evidence varies depending upon the health problem in question, and associations are typically modest.
With respect to war-zone or combat exposure, a small number of studies suggest that such exposure is associated with self-reported short-term and chronic health complaints and conditions, as well as higher levels of medical help-seeking. On the other hand, little definitive evidence indicates that war zone or combat exposure as such contributes to actual physical disease. In several studies of war veterans in which a relationship between stress exposure and self-reported physical health problems were observed, these findings have not been borne out by objective medical examination.
Deriving conclusions about the possible contribution of stress solely from consideration of the range of conditions suffered by participants in the Gulf War clinical registries cannot be done with any degree of certainty. Although the general scientific literature has implicated stress exposure as a contributing factor in various well-defined conditions, including some health problems experienced by Gulf War veterans, few problems or symptoms are uniquely characteristic of stress exposure. Thus, with the possible exception of PTSD, the stress of Gulf War service cannot be conclusively determined to have played a contributing role merely from the observed presence of these disorders or symptoms.
Similarly, although some of the symptoms reported by those registry participants with ill-defined conditions seem consistent with stress exposure, these symptoms are also consistent with various other possible etiologies. In sum, the possibility that stress may have either contributed to or exacerbated the health problems of some registry participants (and, by extrapolation, some Gulf War veterans) can neither be ruled out nor proven based upon currently published descriptive registry data.
A small body of studies, however, directly examined the association between Gulf War stress exposure and subsequent health problems in veterans. In the main, available research focused on the relationship between stress exposure and PTSD symptoms, perhaps owing to the importance of this health problem in the last major war, Vietnam. A secondary focus of available research centered on detecting other psychological health consequences of stress exposure. By contrast, we found very few studies that were designed or reported in a manner that permits conclusions concerning the relationship between stress exposure and bodily symptoms. Although a few studies examined the relationship between stress exposure and self-reported bodily symptoms or functional impairment, we identified no research studies in which stress was adequately assessed that simultaneously attempted to corroborate subjective health complaints with either physical examination or laboratory test procedures.
In general, although hampered by the previously described methological limitations, the available empirical research on samples of Gulf War veterans indicates that stress exposure was associated with PTSD or PTSD-like symptoms. With respect to other psychological problems, the data were somewhat less conclusive. Still, the majority of studies tended to support an association between stress exposure and psychological distress. For both PTSD and other psychological health problems, the association between stress exposure and health problems was generally modest, but more marked in persons exposed to high-stress (combat-related) conditions. By contrast, little evidence links stress exposure to an increase in self-reported bodily symptoms, in part because of the paucity of research on this topic.
Although it is inappropriate to rely upon stress exposure as a default explanation for the myriad health problems reported by Gulf War veterans in the absence of a thorough review of research concerning all plausible causes, we think it equally inappropriate to assume that stress played no role. To do so would ignore what the scientific literature shows about the relationship between stress and health.