Abstract
ObjectivePlacebo effects on cognitive performance and mood and their underlying mechanisms have rarely been investigated in adolescents. Therefore, the following hypotheses were investigated with an experimental paradigm: (1) placebo effects could be larger in adolescents than in adults, (2) parents’ expectations influence their adolescents’ expectations and placebo effects, and (3) a decrease in stress levels could be an underlying mechanism of placebo effects.MethodsTwenty-six healthy adolescents (13.8 ± 1.6 years, 14 girls) each with a parent (45.5 ± 4.2 years, 17 mothers) took part in an experimental within-subjects study. On two occasions, a transdermal patch was applied to their hips and they received an envelope containing either the information that it is a Ginkgo patch to improve cognitive performance and mood, or it is an inactive placebo patch, in counterbalanced order. Cognitive performance and mood were assessed with a parametric Go/No-Go task (PGNG), a modification of California Verbal Learning Test, and Profile of Mood Scales (POMS). Subjects rated their expectations about Ginkgo’s effects before patch application as well as their subjective assessment of its effects after the tests. An electrocardiogram and skin conductance levels (SCLs) were recorded and root mean square of successive differences (RMSSD), high-frequency power (HF), and the area under the curve of the SCL (AUC) were analyzed as psychophysiological stress markers.ResultsExpectations did not differ between adolescents and parents and were correlated concerning reaction times only. Overall, expectations did not influence placebo effects. There was only one significant placebo effect on the percentage of correct inhibited trials in one level of the PGNG in adolescents, but not in parents. RMSSD and HF significantly increased, and AUC decreased from pre- to post-patch application in adolescents, but not in parents.ConclusionWith this experimental paradigm, we could not induce relevant placebo effects in adolescents and parents. This could be due to aspects of the study design such as application form and substance, and that healthy subjects were employed. Nevertheless, we could show that adolescents are more sensitive to psychophysiological reactions related with interventions which could be part of the underlying mechanisms of placebo effects in adolescents.
Highlights
The term “placebo effect” can be described as a symptom improving effect of a drug without an active agent; for example in the context of placebo-controlled, randomized clinical trials (RCTs)
Expectations of Ginkgo effects did not differ between adolescents and parents in general and were significantly correlated between adolescents and their own parent concerning effects on reaction times only (Table 1)
There was only one significant correlation between the expectation of the effects on mood and the placebo effect on negative mood in parents (r = −0.523, p = 0.013, adjusted p = 0.156), whereas there was no correlation between expectations and placebo effects in adolescents
Summary
The term “placebo effect” can be described as a symptom improving effect of a drug without an active agent; for example in the context of placebo-controlled, randomized clinical trials (RCTs). A placebo response is defined as the effectiveness of a placebo on symptoms in the context of RCTs, whereas the placebo effect is part of a symptom change, which can be directly attributed to placebo mechanisms such as expectations or learning mechanisms after eliminating external unspecific factors and statistical artifacts [1, 2]. In a recent review about factors predicting placebo responses, it was concluded that placebo responses mainly appear to be moderated by expectations of how the symptom might change after treatment, or expectations of how symptom repetition can be coped with [4]. A handful of moderators—circumstances under which placebo effects occur—have been discussed, among them are age, sex, and personality traits [4, 5]
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