Open-Label Placebos Reduce Hair Cortisol Concentrations And Psychological Distress: A Randomized Controlled Trial

June 2026 in “ Scientific Reports ”

Carla Liedtke, Michael Schaefer, Sören Enge

open-label placebo hair cortisol concentrations psychological distress stress-management interventions

TLDR Open-label placebos can reduce stress and improve exam performance.

This study investigated the effects of open-label placebo (OLP) treatments on hair cortisol concentrations (HCC) and psychological distress in 134 healthy university students facing stressful oral exams. Participants were randomized into an OLP group, receiving placebo pills, or a control group without treatment. Over four weeks, the OLP group showed a decrease in HCC, indicating a long-term physiological effect of OLPs similar to other stress-management interventions. Additionally, the OLP group experienced reduced psychological distress, and improvements in exam grades were mediated by reduced pre-exam negative affect. These findings suggest that OLPs can mitigate both physiological and psychological impacts of stress.

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