The purpose of this study was to explore the contribution of psychological state to both the ventilatory response and the intensity of dyspnea experienced after the addition of small inspiratory loads to breathing. We hypothesized that patients with either a specific psychiatric diagnosis or a specific psychological trait will associate a greater degree of dyspnea with a loaded breathing task than will control subjects. To insure the inclusion of persons with relevant psychological profiles, we recruited both subjects enrolled in the Chronic Fatigue Center and normal control subjects. In all, 52 subjects inspired first through a small (1.34 cm H(2)O/L/s) and second through a moderate (3.54 cm H(2)O/L/s) inspiratory resistive load (IRL). Ventilation was monitored throughout the 5-min sessions. Dyspnea was quantified with the Borg scale at specified times during the protocol. Standard psychological tests were administered. We found that subjects could be divided into two groups. One, the "responders," reported Borg scores higher than those of the second, or "nonresponder" group, at all times during the protocol. By contrast, there was no difference between groups with respect to ventilation. Responders had higher scores on tests of depression (the Center for Epidemiological Study depression scale) than did nonresponders. We conclude that the variability observed in subjective responses to IRL is explained, in part, by differences in psychological state.