Imaginary pills and open-label placebos can reduce test anxiety by means of placebo mechanisms

Abstract

Placebos have been shown to be beneficial for various conditions even if administered with full transparency. Hence, so-called open-label placebos (OLPs) offer a new way to harness placebo effects ethically. To take this concept one step further, this study aimed at evaluating placebo effects without the use of a physical placebo, i.e., by imagining taking a pill. Healthy students (N = 173) with self-reported test anxiety were either randomized to an imaginary pill (IP; n = 55), an OLP (n = 59) or a control group (CG; n = 59). Both intervention groups were instructed to take two pills daily for three weeks. Primary outcome was test anxiety, secondary outcomes were sleep quality, general well-being and test performance. Groups test anxiety differed at study-endpoint, F(2,169) = 11.50, p < .001. Test anxiety was lower in the intervention groups compared to the CG, t(169) = - 4.44, p < .001, d = - 0.71. The interventions did not differ significantly, i.e., both were similarly efficacious, t(169) = 0.61, p = .540, d = 0.11. The interaction between group and time in explaining test anxiety was significant, F(5,407.93) = 6.13, p < .001. OLPs and IPs reduced test anxiety in healthy participants compared to the CG. This finding opens the door for a novel and ethical method to harness placebo effects.

Figure 1

CONSORT diagram. Flow of the study, including reasons for exclusions.

Figure 2

Mean improvement in test anxiety (PAF: test anxiety questionnaire) from baseline (T1) to endpoint (T4) per group. Results indicate a significant improvement for the OLP and IP group compared to the CG. Note. CG control group, IP  imaginary pill, ns = not significant, OLP open-label placebo, ***p < .001. Error bars represent standard error of the mean.

Figure 3

Boxplot showing continuous grades of the participants per group. Every dot represents a participants’ grade with higher grades being better (ranging from 1.0 to 6.0). Note. Median is represented by the bold line within the box and upper/lower quartiles mark the end of the box. CG control group, IP imaginary pill, OLP open-label placebo.

Figure 4

Course of test anxiety over time. Mean test anxiety per group from baseline (T1) through midpoints (T2, T3) to study endpoint (T4). Note. Error bars represent standard error of the mean. CG control group, IP imaginary pill, OLP  open-label placebo.

Figure 5

Procedure of the study. Note: ASS-SYM Änderungssensitive Symptomliste (general well-being), EoR expectancy of test anxiety relief, PAF Prüfungsangstfragebogen (test anxiety questionnaire), PSQI pittsburgh sleep quality index, SEs side-effects, SDD sociodemographic data.