Placebo responses: An experimental study of psychophysiological processes in asthmatic volunteers

Abstract

This study evaluated the effects of placebo medication on pulmonary responses in asthmatics, and investigated the roles of expectancy and anxiety. Twelve adult asthmatics were recruited for a laboratory experiment described as a study of the effectiveness of a new bronchodilator. Distilled nebulized water was inhaled in each session. The solution was described as water in session 1 (control), while in sessions 2 and 3 subjects were told that the nebulizer contained a chemical likely to cause chest tightness and wheezing (bronchoconstrictive suggestion). Prior to the inhalation sequence in sessions 2 and 3, subjects inhaled from an aerosol that they were told contained either a powerful new drug (placebo) or a non-active substance (neutral). Pulmonary function was measured with the forced oscillation technique and spirometry, while autonomic parameters, anxiety and expectancies were also monitored. Pulmonary function deteriorated following the inhalations accompanied by bronchoconstrictive suggestion, and this effect was abolished by pre-treatment with placebo. Neither subject expectations nor changes in anxiety were associated with the experimental manipulations. The implications of these results for theories of placebo action are considered.