title: Stress-related and basic determinants of hair cortisol in humans: A meta-analysis.
abstract: The analysis of hair cortisol concentrations (HCC) is a relatively new strategy to measure long-term cumulative cortisol levels, which is increasingly used in psychoneuroendocrinological research. Here, we conduct a first comprehensive meta-analysis of HCC research based on aggregated data from a total of 124 (sub)samples (66 independent studies; total N=10,289). We seek to answer two central questions: (i) Which covariates and basic features of HCC need to be considered in future research? (ii) What are the main determinants of HCC in terms of chronic stress exposure and mental health? Concerning basic characteristics, our findings identify several covariates to be considered (age, sex, hair washing frequency, hair treatment, oral contraceptive use), confirm a decline of HCC from the first to the second proximal 3cm hair segment, and show positive associations between HCC and short-term salivary cortisol measures. Regarding chronic stress, we show that stress-exposed groups on a whole exhibit 22% increased HCC. This long-term cortisol hypersecretion emerges particularly when stress is still ongoing at the time of study (+43% HCC) but is not present in conditions of past/absent stress (-9% HCC, n.s.). We also report evidence for 17%-reduced HCC in anxiety disorders, such as PTSD. Interestingly, no consistent associations with mood disorders and self-reports of perceived stress, depressiveness or social support are found. However, our findings reveal positive associations of HCC with stress-related anthropometric (body mass index, waist-to-hip ratio) and hemodynamic measures (systolic blood pressure). These meta-analytic results are discussed in the light of their practical implications and important areas for future inquiry are outlined.
authors.affiliation: Biological Psychology, TU Dresden, Dresden, Germany; Clinical Psychology, University of Siegen, Siegen, Germany. Electronic address: tobias.stalder@psychologie.uni-siegen.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Stalder
authors.affiliation: Biological Psychology, TU Dresden, Dresden, Germany.
authors.forename: Susann
authors.initials: S
authors.lastname: Steudte-Schmiedgen
authors.affiliation: Biological Psychology, TU Dresden, Dresden, Germany; Differential and Personality Psychology, Medical School Hamburg, Hamburg, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Alexander
authors.affiliation: Clinical Psychology, University of Siegen, Siegen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Klucken
authors.affiliation: Biological Psychology, TU Dresden, Dresden, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Vater
authors.affiliation: Biological Psychology, TU Dresden, Dresden, Germany.
authors.forename: Susann
authors.initials: S
authors.lastname: Wichmann
authors.affiliation: Biological Psychology, TU Dresden, Dresden, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Kirschbaum
authors.affiliation: Biological Psychology, TU Dresden, Dresden, Germany; Faculty of Natural Sciences, Medical School Berlin, Berlin, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Miller
mesh_terms: D006197:Hair / Q000737:chemistry*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D013315:Stress, Psychological / Q000503:physiopathology*
chemical_list: D006854:Hydrocortisone
keywords: Confounder; Hair cortisol; Meta-analysis; Stress; Validity