One-of-four Gulf War Veterans (GWV) are affected by GWI. Why are they reluctant to volunteer for ongoing clinical research and trials?

"Gulf War illness (GWI) is a serious condition that affects at least one fourth of the 697,000 U.S. veterans who served in the 1990-1991 Gulf War. This complex of multiple concurrent symptoms typically includes persistent memory and concentration problems, chronic headaches, widespread pain, gastrointestinal problems, and other chronic abnormalities not explained by well-established diagnoses. No effective treatments have been identified for Gulf War illness and studies indicate that few veterans have recovered over time. "Research Advisory Committee on Gulf War Veterans’ Illnesses U.S. Department of Veterans Affairs Washington, D.C.