evidence of association between deployment to the Gulf War and chronic multisymptom illness” (p. 210), that “the excess of unexplained medical symptoms reported by deployed Gulf War veterans cannot be reliably ascribed to any known psychiatric disorder” (p. 109), and that the unexplained symptoms might “result from interplay between … biological and psychological factors” (p. 260).

A number of IOM reports have examined associations between health outcomes and exposures that military personnel may have been subject to during their service in the 1991 Gulf War—chemical exposures (for example, to combustion products, pesticides, pyridostigmine bromide, sarin, and solvents), biologic exposures (for example, to infectious agents and vaccines), and physical exposures (for example, to depleted uranium) (IOM, 2000, 2003, 2004, 2005, 2006a,b, 2007, 2008, 2010a). In sum, those reports did not find evidence that would support a confident attribution of the array of unexplained symptoms reported by veterans of the 1991 Gulf War to any specific chemical, biologic, or physical exposure.

There is a lack of consensus among expert groups regarding the cause of CMI in 1991 Gulf War veterans. Most experts who have studied the issue have not identified what they consider to be a likely cause of CMI. However, the Department of Veterans Affairs (VA) Research Advisory Committee on Gulf War Veterans’ Illness (RAC) conducted a review of the evidence and concluded that Gulf War illness was causally associated with use of pyridostigmine bromide pills and exposure to pesticides used during deployment (RAC, 2008). IOM reviewed the epidemiologic and experimental studies cited in the RAC report and concluded that the evidence was not robust enough to establish a causal relationship between pyridostigmine bromide or pesticides and CMI (IOM, 2010a).

Despite many years of research, there is no consensus among physicians, researchers, and others as to the cause of CMI in 1991 Gulf War veterans, and there is a growing belief that a causal factor or agent may not be identified (IOM, 2010a; Mahoney, 2001). It is also possible that an underlying physiologic abnormality may not be identified. The 2010 IOM committee recommended “a renewed research effort with substantial commitment to well-organized efforts to better identify and treat multisymptom illness in Gulf War veterans” (IOM, 2010a).


The present study was mandated by Congress in the Veterans Benefits Act of 2010 (Public Law 111-275, October 13, 2010). The law directs the secretary of veterans affairs “to enter into an agreement with the Institute of Medicine of the National Academies to carry out a comprehensive review of the best treatments for CMI in Persian Gulf War veterans and an evaluation

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