crowding in base camps, long duty days, being fired on by the enemy, and noise from guns and artillery.

Kulka et al. (1990) asked Vietnam veterans about both war-zone stressors and traumatic events for the National Vietnam Veterans Readjustment Study (NVVRS). They distinguished between the two with the understanding that exposure to war-zone stress, such as being on frequent long-range patrols in hostile enemy territory, could increase the risk of exposure to a traumatic event, such as being in an ambush in which their colleagues were killed or wounded. Male veterans were asked 94 questions about war-zone stress exposures: 48 items about exposure to combat, 24 items about exposure to abusive violence and related conflicts, 12 items about deprivation, 9 items about loss of meaning and control, and 1 item about ever having been a prisoner of war in Vietnam. They found that 75% of veterans with high levels of war-zone stress also had exposure to at least one traumatic event during the war, and one-third of theater veterans with low war-zone stress described at least one traumatic experience. When war-zone combat exposure based on military records was compared with self-reports of combat exposure, Dohrenwend et al. (2006) found that 96.5% of Vietnam veterans who were classified as having low combat exposure on the basis of their military records reported having low or moderate exposure, and 72.1% of those classified as having very high combat exposure reported high exposure.

Fontana and Rosenheck (1999) used NVVRS data to identify important war-zone stressors. Primary stressors are killing or injuring others and insufficiency (inadequate food, inadequate water, inadequate weapons or munitions, inadequate equipment or supplies, loss of freedom of movement, and lack of privacy)—part of what King et al. (1995) called a malevolent environment. Other studies of Vietnam veterans indicate that participating in or witnessing atrocities against the enemy or civilians, both dead and alive, can be an important stressor (Fontana and Rosenheck 1999; King et al. 1995).

Schlenger et al. (1992) sought to develop a comprehensive exposure measure that would capture the array of war-zone stressors. They used principal-component analysis of the 100 interview items on the National Survey of the Vietnam Generation (part of the NVVRS) to develop a list of major stressors for men and women. For men, the stressors were exposure to combat (such as frequency of receiving enemy small-arms fire), abusive violence and related conflict (such as involvement in mutilation of bodies), deprivation (such as lack of shelter from weather), and loss of meaning and control (such as a sense of purposelessness). For women, the stressors were exposure to dead and wounded (such as frequency of giving care to people who later died), exposure to enemy fire (such as frequency of being under enemy fire), direct combat involvement (such as frequency of firing a weapon in a combat situation), exposure to abusive violence (such as seeing or hearing of Americans who had been tortured), deprivation (such as frequency of fatigue or exhaustion), and loss of meaning and control (such as feeling out of touch with the world).

In Operation Enduring Freedom (OEF) and OIF, many of the stressors are more reminiscent of the Vietnam War than of the 1991 Gulf War or World War II. With the defeat of the Iraqi Army and later sectarian violence, U.S. troops have been subjected to guerilla warfare and terrorist actions from civilian insurgents and militias; soldiers must be constantly on guard against snipers, improvised explosive devices (IEDs), and suicide bombers; and all civilians must be viewed with caution.

In 2003, Hoge et al. (2004) surveyed 2856 Army and 815 Marine combat infantry troops before and several months after their deployment to Iraq and Afghanistan for the Army units and



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