Diurnal cortisol slopes and mental and physical health outcomes: A systematic review and meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational studies
PubMed 28578301 · doi:10.1016/j.psyneuen.2017.05.018
What was done
The authors conducted a systematic review and meta-analysis of literature published up to January 31, 2015, evaluating associations between diurnal cortisol slopes (changes from morning to evening cortisol levels) and mental and physical health outcomes. Analyses combined 179 effect size associations from 80 included studies and evaluated potential moderators such as slope measurement method and study quality metrics.
What was found
Across all included studies, flatter diurnal cortisol slopes were significantly associated with poorer overall health, yielding an average effect size of r = 0.147. Flatter slopes correlated with worse health in 10 out of 12 evaluated subtypes of emotional and physical health outcomes, with the largest effect size observed for immune and inflammation outcomes (r = 0.288).
Why it matters
This review provides quantitative synthesis across 80 studies linking blunted circadian cortisol rhythms to adverse physical and psychological health, highlighting an especially prominent link with immune and inflammatory dysregulation.
Limits
The underlying studies are observational, limiting causal determination of whether flattened slopes are an etiological mechanism or a consequence of disease. Total participant count, exact confidence intervals, and longitudinal versus cross-sectional breakdowns are not provided in the abstract.
Cited by
- supports A flattened diurnal cortisol curve predisposes individuals to insomnia and anxiety.