Contemplative mental training reduces hair glucocorticoid levels in a randomized clinical trial

Objective To investigate the effect of regular contemplative mental training on endocrine and psychological indices of long-term stress. Methods An open-label efficacy trial that comprised three distinct 3-month modules targeting attention and interoception, socio-affective or socio-cognitive abilities through dyadic exercises and secularised meditation practices was conducted with healthy adults. Participants underwent the training for three months, nine months, or were assigned to a retest control cohort. Chronic stress indices were assayed at four timepoints: pre-training and after three, six and nine months. The main outcome measures were cortisol (HC) and cortisone (HE) concentrations in hair and self-reported long-term stress. Results Of 362 initially randomized individuals, 30 dropped out before study initiation (N = 332; mean age-40. 7 ± SD = 9.2 years; 197 women). Hair-based glucocorticoid assays were available from n = 227, and questionnaire data from n = 326. Results from three separate training cohorts (TCs) revealed consistent decreases in HC and HE levels over the first three (TC3) to six months (TC1 and TC2) of training, with no further reduction at the final 9-month mark (baseline to end-of-training, HC: TC1, t(355) = 2.59, p = .010; est.:0.35[0.14]; TC2, t(363) = 4.06, p < .001; est.:0.48[0.12]; TC3: t(368) = 3.18, p = .002; est.:0.41[0.13]; HE: TC1, t(435) = 3.23, p = .001; est.:0.45[0.14]; TC2: t(442) = 2.60, p = .010; est.:0.33[0.13]; TC3: t(446) = 4.18, p < .001; est.:0.57[0.14]). Training effects on HC increased with practice frequency, and effects on both HC and HE were independent of training content and unrelated to change in self-reported chronic stress. Self-reported stress, and cortisol to dehydroepiandrosterone ratios as an exploratory endpoint, were also reduced, albeit less consistently. Conclusions Our results point to the reduction of long-term cortisol exposure as a mechanism through which contemplative mental training may exert positive effects on practitioners' health. Trial registration: ClinicalTrials.gov identifier: NCT01833104