reported chronic conditions and symptoms of a variety of derived clinical outcomes¹¹ (chronic fatigue, cognitive dysfunction, multiple chemical sensitivities, major depression, PTSD, chronic dysphoria, anxiety, fibromyalgia, and respiratory diseases). The greatest differences between deployed and nondeployed forces were in the first three outcomes. The symptom grouping with the highest overall prevalence was cognitive dysfunction, which occurred in 34–40 percent of Gulf War veterans compared with 10–15 percent of control veterans. Gulf War veterans also reported significantly more visits to health care practitioners, greater dissatisfaction with health, and greater reductions in recent activity because of health than control veterans.

Symptom clustering. The Canadian study did not search for potentially new syndromes.

Exposure–symptom relationships. In Canadian Gulf War veterans, the greatest number of symptom groupings were associated with self-reported exposures to psychological stressors and physical trauma. Several symptom groupings also were associated with exposure to chemical warfare agents, nonroutine immunizations, sources of infectious diseases, and ionizing or nonionizing radiation. Nevertheless, a subset of Canadian veterans who could not have been exposed to many of the agents, because they were based at sea, reported symptoms as frequently as did land-based veterans in this study.