A field (researcher's) guide to cortisol: tracking HPA axis functioning in everyday life

Researchers have been incorporating ambulatory cortisol sampling into studies of everyday life for over a decade. Such work provides an important supplement to acute laboratory stress paradigms and provides a novel perspective on the interrelationships between stress, psychological resources, and health. However, the results of many field studies have been inconclusive and more studies have been undertaken than published. We describe some of the challenges facing naturalistic cortisol researchers, including lack of power, methodological and analytical problems, and patterns of confusing or conflictual results. We then summarize key findings of published naturalistic cortisol studies to date, grouped by type of cortisol outcome (morning awakening response, diurnal slope, area under the curve, and associations between momentary experiences and cortisol). We propose research questions relevant to everyday stress researchers and suggest next steps for researchers who are interested in incorporating naturalistic cortisol sampling into future studies.