to the prevalence among disabled veterans of other wars. Reports on somatization disorder in Gulf War veterans also do not support such an attribution. Somatization disorder, which is rare, requires eight symptoms that are not caused by a medical illness. Fiedler et al. (2006) and Toomey et al. (2007) found almost no cases of somatization disorder among Gulf War veterans, nor was there a significant elevation in somatization disorder among deployed versus nondeployed veterans. Therefore, somatization disorder cannot account for the high prevalence of medically unexplained disability in Gulf War veterans.
Finally, studies of somatoform disorder in Gulf War veterans also do not support the hypothesis that their medically explained symptoms results from this disorder. Somatoform disorder includes many specific diagnoses, of which the most relevant for this report is undifferentiated somatoform disorder. This disorder requires only one symptom without known medical causes, and is therefore a relatively common and nonspecific diagnosis. In the study by Ismail et al. (2002), somatoform disorder was more common in deployed versus nondeployed Gulf War veterans (16% vs 6%) and also more common in disabled Gulf War veterans than in disabled veterans from other wars (16% vs 7%). It was, however, present in only a small minority of disabled Gulf War veterans (after exclusion of those with known diseases, see above). Furthermore, the medical investigations in this study were not sufficiently comprehensive to rule out medical explanations for the symptoms in those who did have somatoform disorder.
Therefore, the committee concludes there is sufficient evidence of a causal relationship between traumatic war exposures experienced during deployment to the Gulf War and PTSD. The committee also concludes that there is sufficient evidence of an association between deployment to the Gulf War and other psychiatric disorders, including generalized anxiety disorder and substance abuse, particularly alcohol abuse. Furthermore, these disorders persist for at least 10 years after deployment. Finally, the excess of unexplained medical symptoms reported by deployed Gulf war veterans cannot be reliably ascribed to any known psychiatric disorder.