Stephen Boyle of Duke University Medical Center in North Carolina says that people who are cynical, suspicious of other people and their motives, are 25% more likely to develop heart disease. Boyle postulates that distrust of others creates greater stress and hostility, which can cause spikes in an immune-system protein called C3 that has been linked with various diseases, including diabetes. The participants (more than 300 Vietnam War veterans) with higher scores on hostility showed an increase in these proteins, while the non-hostile men showed no such increase.