In this edition of Psychological Medicine, research findings are reported from two studies of British Gulf War veterans (David et al. 2002; Everitt et al. 2002). Both studies were carried out at King's College ‘Gulf War Illness Research Unit’, which was established in 1996. The two studies were conducted to examine the causes of unexplained symptoms among Gulf War veterans. The results presented in these papers are important because they were derived from well-designed studies that employed a randomized sample of Gulf War veterans and two control populations of non-deployed ‘era’ veterans who served in the early 1990s and troops who participated in another hazardous deployment to Bosnia.

In one study, cognitive function and mood disturbances were evaluated using a comprehensive battery of neuropsychological tests and rating scales (David et al. 2002). A significant proportion of Gulf War veterans reporting ill health were found to have both lower cognitive function scores and depressed mood compared to well Gulf War veterans, era veterans and Bosnia troops. Importantly, a strong association was found between depressed mood and poor performance on cognitive function tests. It is noteworthy that among ill Gulf War veterans, most cognitive function measures were within the normal range, although they were significantly lower than those of controls.

Based on these and related research findings, the study investigators concluded that lower performance on cognitive function tests could be explained primarily by mood disturbances. However, they could not rule out the possibility that cognitive difficulties had led to depressed mood or that a neurotoxic environmental exposure had caused both health problems.