Cortisol concentration

Method

Cortisol concentration in serum, plasma or saliva by immunoassay or LC-MS/MS, pooled as a mean difference. The matrix, the clock time of sampling, and whether the value is a single point, an awakening response, or a diurnal area under the curve are recorded on the edge - these are not interchangeable and cortisol varies several-fold across the day.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

Serum and salivary cortisol were pooled together in the source reviews despite measuring different fractions - saliva tracks free cortisol, serum tracks mostly protein-bound - which is why the matrix flag is mandatory. The near-miss is CAT:outcome/perceived-stress-scale-score and the pooled perceived-stress node: reported together under a stress heading, both falling with benefit, but the dissociation between subjective stress and cortisol is well documented, and an edge treating one as evidence for the other asserts a link the data do not support. Direction is also population-bound - in adrenal insufficiency a rise is the benefit.