Solidifying fundamental methodological practices of hair cortisol analysis: an investigation into the influence of storage duration, scalp region and sampling method on hair cortisol results

• Applicant: Dr. Tobias Stalder
• Subject Area: Biological Psychology and Cognitive Neuroscience
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 503208201

Hair cortisol analysis is a method for the assessment of long-term cumulative hormone concentrations, which is widely used in biopsychological stress research. However, despite its popularity, there are still central aspects of methodological practices employed in hair cortisol analysis that currently lack any systematic empirical evaluation. Three critical questions that hair cortisol researchers are regularly faced with include: (i) How long can hair samples can be stored before biochemical analysis? (ii) From which area of the scalp should hair best be sampled? And, (iii) is the required amount of hair best derived from a single larger sample or by pooling material from different locations? The proposed project sets out to provide a first systematic investigation into these critical questions by means of three carefully-designed within-subject studies. Study I investigates the influence of sample storage for 0, 3, 6, 12 or 24 months using intra-individually homogenized hair material and a distributed sampling scheme. Study II compares hair sampling from the posterior vertex and the occipital region, i.e. the two most promising scalp areas, while study III contrasts data quality between the single-sample vs. the accumulation method. Each of the three studies focuses on (a) internal statistical outcomes (means and variability, internal consistency, reliability) and (b) the impact of methodological choices on strength of association with relevant external criteria (anthropometrics and life stress exposure). We believe that this project will help solidify fundamental practices of hair cortisol research, thus allowing researchers to make evidence-based methodological choices and improving the quality of future research.

• DFG Programme: Research Grants
• International Connection: USA
• Co-Investigators: Privatdozent Dr. Johannes Finke; Dr. Kristian Kleinke; Professor Dr. Tim Klucken
• Cooperation Partner: Dr. George M. Slavich