Summary: Many people report that meditation reduces daily stress. A new randomized clinical trial from the Max Planck Institute provides objective physiological evidence supporting these claims: cortisol levels measured from hair samples fell by about 25% after six months of structured meditation training.
Source: Max Planck Institute
Mental training designed to strengthen skills such as mindfulness, attention, gratitude and compassion lowers long-term exposure to the stress hormone cortisol, as measured in hair. Researchers at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig and the Social Neuroscience Research Group of the Max Planck Society in Berlin report these findings from a large-scale randomized study.
Hair cortisol concentration is a validated marker of chronic stress exposure because cortisol produced during prolonged stress accumulates in hair as it grows. Previous studies often relied on self-reported stress or short-term cortisol measures; this study adds an objective, physiological indicator of sustained stress relief after contemplative mental training.
Chronic stress affects a substantial portion of the population—one study cited in Germany found roughly 23% of people report frequent stress—and contributes to a range of health problems, including cardiovascular disease, diabetes and mental disorders such as depression. Effective, scalable strategies for reducing everyday stress are therefore a public health priority.
Mindfulness and contemplative trainings aim to improve cognitive and social-emotional skills through meditation practices and dyadic exercises. While earlier eight-week interventions showed reductions in perceived stress, it was unclear whether such programs reduce sustained cortisol exposure over longer periods. Self-report questionnaires can inflate perceived benefits through expectation and social desirability bias, because participants know the intervention is intended to reduce stress.
To avoid reliance on self-report alone, the research team used hair-based glucocorticoid assays to track long-term cortisol and cortisone levels across a nine-month training period. Hair grows about one centimetre per month, so sampling the first three centimetres from the scalp captures cortisol exposure across approximately three months. Samples were collected every three months and analysed in collaboration with the laboratory of Clemens Kirschbaum at the University of Dresden.
The mental training was part of the ReSource Project, a longitudinal study led by Tania Singer. The program comprised three distinct 3-month modules, each targeting a different skill set with secularized Western and Eastern contemplative practices: attention and mindfulness (interoception), socio-affective skills (compassion and gratitude), and socio-cognitive skills (perspective-taking). Participants practiced about 30 minutes per day, six days a week, and three cohorts completed the modules in different orders to control for sequence effects.
Less stress, less cortisol
Consistent results emerged across the training cohorts: hair cortisol concentrations decreased significantly over the course of training, with the most pronounced change visible after six months. On average, participants exhibited a roughly 25% reduction in hair cortisol compared with baseline. Initial small reductions appeared during the first three months and increased through month six, while levels remained lower during the final three months.
These findings suggest that sufficiently long training—months rather than weeks—is required to achieve measurable reductions in long-term physiological stress markers. Importantly, the reduction in cortisol did not depend strongly on which training module participants completed first; different contemplative skills appeared similarly effective at lowering chronic cortisol accumulation. Training compliance mattered: participants who practiced more frequently experienced larger declines in hair cortisol.
Earlier analyses from the same ReSource sample examined acute stress responses. In that study, participants were exposed to socially evaluative stressors such as simulated job interviews and difficult mental arithmetic under observation. Those who received socio-cognitive or socio-affective training showed much smaller acute cortisol surges in saliva—up to a 51% reduction compared with untrained controls—indicating improvements in handling immediate stressors as well as chronic daily stress.
Taken together, the studies indicate that contemplative mental training can improve how people respond to acute social stress and reduce ongoing physiological stress exposure. “Different training components appear to be particularly helpful for different forms of stress,” says Veronika Engert, head of the Social Stress and Family Health group. Lara Puhlmann, the study’s first author, adds that objective physiological measures are increasingly important in mindfulness research because participants’ expectations can bias self-reported outcomes.
Long-term stress contributes to many global health burdens, including depression. By demonstrating a reduction in long-term cortisol exposure with meditation-based interventions, the study supports the preventive potential of contemplative training to protect health in otherwise healthy individuals.
About this stress research news
Author: Verena Müller
Source: Max Planck Institute
Contact: Verena Müller – Max Planck Institute
Image: The image is credited to Max Planck Institute
Original Research: Open access. “Contemplative Mental Training Reduces Hair Glucocorticoid Levels in a Randomized Clinical Trial” by Puhlmann, L.; Vrtička, P.; Linz, R.; Stalder, T.; Kirschbaum, C.; Engert, V.; Singer, T. Psychosomatic Medicine.
Abstract
Contemplative Mental Training Reduces Hair Glucocorticoid Levels in a Randomized Clinical Trial
Objective
This study assessed whether regular contemplative mental training affects endocrine and psychological indicators of long-term stress.
Methods
An open-label trial evaluated three distinct 3-month modules targeting attention/interoception, socio-affective, or socio-cognitive abilities through dyadic exercises and secular meditation practices in healthy adults. Participants trained for 3 or 9 months or were assigned to a retest control cohort. Chronic stress markers were measured pretraining and after 3, 6, and 9 months. Primary outcomes were cortisol and cortisone concentrations in hair, alongside self-reported long-term stress.
Results
Of 362 randomized individuals, 332 began the study (mean age 40.7 years, 197 women). Hair glucocorticoid assays were available for 227 participants and questionnaire data for 326. Across three training cohorts, hair cortisol and cortisone levels declined steadily during the first three to six months of training, with no further decrease by month nine. Training effects on hair cortisol correlated with individual practice frequency, were independent of the specific training content, and were not strictly mirrored by changes in self-reported stress. Exploratory endpoints, including self-reported stress and cortisol-to-dehydroepiandrosterone ratios, showed reductions that were less consistent.
Conclusions
The results indicate that meditation-based mental training reduces long-term cortisol exposure, suggesting a physiological mechanism by which contemplative practice may benefit health.
Trial Registration: ClinicalTrials.gov identifier: NCT01833104.