The association between psychological resilience and hair cortisol concentration in adults: A systematic review and meta-analysis

Background Available resilience measurement is based on subjective self-assessment, which is prone to bias. Objective biological/physiological measures of resilience are therefore needed. Hair cortisol concentration is a promising candidate as a biomarker for resilience. Methods We conducted a meta-analytic review from inception to April 2023 in PubMed, EMBASE, Cochrane Library, and Psych Info. All data were analyzed using a random-effects model. Results Eight studies were identified that included a total of 1064 adults. The random-effects model showed that resilience and hair cortisol concentration was inversely correlated (r = -0.18, 95% confidence interval [CI] = -0.27 to -0.09) with substantial heterogeneity (I- 2 = 54.2%, p = 0.03). The inverse association was stronger in those who were 40 years or younger compared to those who were over 40 years. The correlation coefficients between psychological resilience and hair cortisol concentration among adults assessed by different resilience measures were r = -0.29 (95% CI = -0.49 to -0.08) for the CD-RISC-10; r = -0.21 (95% CI = -0.31 to -0.11) for the CD-RISC-25, and r = -0.08 (95% CI = -0.22 to 0.06) for the BRS. Six of eight studies explored the connection between resilience and perceived stress, where the weighted mean correlation coefficient was r = -0.45 (95% CI = -0.56 to -0.33), with considerable heterogeneity (I- 2 = 76.2%, p = 0.001). Conclusions There is a negative association between psychological resilience and hair cortisol concentration, based on these eight studies. Additional research, particularly prospective studies, is needed to determine whether hair cortisol concentration can be used as a biomarker for psychological resilience.