• Katleen Bogaerts, Li Wan, Diest Ilse Van IV, Linda Stans, Marc Decramer, and Omer Van den Bergh.
• Research Group on Health Psychology, Department of Psychology, University of Leuven, Tiensestraat 102, B-3000 Leuven, Belgium. katleen.bogaerts@ppw.kuleuven.be
• Psychosom Med. 2012 Nov 1; 74 (9): 974-81.

ObjectiveMemory for unpleasant experiences is dominated by intensity at the experience's peak and end, with a relative neglect for its duration. Therefore, unpleasant somatic experiences are expected be remembered as less aversive when they end gradually rather than abruptly, even when they last longer (i.e., the "peak-end effect"). We investigated the peak-end effect for dyspnea in healthy participants and in patients with medically unexplained dyspnea (MUD).MethodsTwo aversive dyspnea-inducing tasks were administered to a clinical MUD sample (n = 29) and a matched healthy control group (n = 29) using a rebreathing paradigm (60-second room air, 150-second rebreathing). In a short trial, the breathing system (mouthpiece) was removed immediately after peak dyspnea. In a long trial, breathing was switched to room air after peak dyspnea and continued in the breathing system for 150 seconds (order was counterbalanced across participants). Respiratory parameters were continuously measured, and dyspnea was rated every 10 seconds. Relative unpleasantness of the dyspneic episode was assessed with forced choice questions.ResultsMore than 70% of the healthy group found the short episode worse than the long one despite equal maximal dyspnea (p = .02). Patients with MUD did not show this peak-end effect (p = .58). The latter had deficient recovery of dyspnea compared with the controls (42.08 [21.86] versus 17.51 [11.18], p < .001), which could not be explained by differences in respiratory physiology.ConclusionsThe peak-end effect in dyspnea has important implications for dyspnea measurement. Its absence in patients with MUD suggests a critical role of distorted perceptual-cognitive processing of aversive somatic sensations in patients with medically unexplained symptoms.

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