A Direct Comparison of Placebo and Nocebo Effects on Visuospatial Attention: An Eye-Tracking Experiment

• Published in: Frontiers in psychiatry Vol. 10; p. 446
• Main Authors: Höfler, Carina, Potthoff, Jonas, Schienle, Anne
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 21-06-2019
• Subjects: eye-tracking; nocebo; placebo; Psychiatry; sham transcranial magnetic stimulation; visuospatial attention; sham transcranial magnetic stimulation; eye-tracking; visuospatial attention; placebo; nocebo
• ISSN: 1664-0640; 1664-0640
• DOI: 10.3389/fpsyt.2019.00446

Placebo and nocebo effects on visual attention are still poorly understood. This eye-tracking study directly compared effects of sham transcranial magnetic stimulation (sTMS) that was administered along with the verbal suggestion that the treatment would either increase (placebo) or decrease (nocebo) left-sided visual attention.
Twenty women who had reported decreased attention (nocebo responders) and 20 women who had reported increased attention (placebo responders) following sTMS completed a visual search task with three visual load levels. The task was conducted once with and once without the placebo or the nocebo (sTMS). Left-sided fixations and reaction times for left-sided targets (in comparison with right-sided targets) were analyzed.
Contrary to the verbal suggestion, the nocebo responders showed more left-sided fixations in the nocebo condition (compared with the control condition) and responded faster to left-sided targets in the high-load condition. The placebo had no effect on fixations and reaction times.
These results indicate a more beneficial effect of a nocebo compared with a placebo for the first time. Limits and possibilities of placebo and nocebo interventions are discussed.