estimated on the basis of responses to the 17-item PTSD Checklist that corresponded to the symptoms in the DSM-III-R. No clinical examinations were conducted for either CFS or PTSD. Compared with nondeployed veterans, Gulf War veterans had a greater risk for both PTSD (12.1% vs 4.3%) and CFS (5.6% vs 1.2%). The OR for current PTSD in deployed vs nondeployed veterans was 3.1 (95% CI 2.7-3.4) and 4.8 (95% CI 3.9-5.9) for CFS; ORs were adjusted for age, marital status, rank, and unit component and PTSD was also adjusted for sex. The authors also attempted to determine the effects of deployment stressors on the risk of PTSD and CFS in the reserve and National Guard units that were activated but not deployed and were deployed to the gulf. Although PTSD increased with intensity of stress, a risk of a CFS-like illness did not show a similar relationship and increased from 0.8% of members who were not activated to 1.7% of members who were activated and deployed but not to the gulf. The risk of having CFS was higher in members deployed to the gulf than deployed elsewhere but did not vary significantly with increasing combat stress, ranging from 5.4% to 7.3%. This study did not identify members who had comorbid PTSD and CFS, nor did it attempt to determine how soon after deployment the symptoms of each disorder were apparent. The study had the advantage of a population-based cohort with a relatively high participation rate of 70%, but it is limited by the lack of a physical examination for CFS or a psychiatric interview for PTSD.

Summary and Conclusions

Because the diagnosis of CFS depends entirely on symptoms, not on physical or laboratory findings, its prevalence varies widely from study to study. The only primary study demonstrated a higher prevalence of CFS in Gulf War-deployed veterans than in nondeployed veterans, although the absolute difference in prevalence was very small (1.6% vs 0.1%). Of the five secondary studies comparing Gulf War-deployed veterans with nondeployed veterans or veterans deployed elsewhere, three showed a higher prevalence of self-reports of CFS, CFS symptoms, or CFS-like illnesses; the other two studies did not see a difference in the prevalence of CFS between the two groups. Of the three secondary studies using the CDC definition of CFS, two had a positive association, and one no association. In addition, some of the secondary studies reviewed were not limited to CFS but included fatigue or CFS-like illnesses.

The committee concludes that there is limited but suggestive evidence of an association between deployment to a war zone and chronic fatigue syndrome.

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