What does the Cortisol Awakening Response test measure?

Why is Cortisol Awakening Response measured?

The CAR is a well-characterised measure in psychoneuroendocrine research, where blunted and exaggerated responses have been associated at group level with chronic stress, burnout, depression, and post-traumatic stress disorder. Its translation to individual clinical decision-making is not established: associations are demonstrated across populations rather than validated for individual diagnosis, no diagnostic thresholds are agreed, and within-person variability across days is substantial. The measure is also unusually vulnerable to protocol error, since delayed waking collection produces a spuriously blunted response that is indistinguishable from a genuine one.

Reference ranges

Standard reference

Method-specific salivary intervals across waking, +30 min, and +60 min samples # REVIEWER FLAG: CAR reference intervals are method-specific — reviewer to confirm against the Precision Analytical salivary protocol and timing.

Functional medicine optimal

A defined post-waking rise is generally regarded as expected; interpreted as a pattern # REVIEWER FLAG: CAR interpretive thresholds are not standardised clinically — reviewer to confirm framing.

Units

nmol/L, µg/dL, nmol/L·min (area under curve), nmol/L (delta), % change, nmol/L increase, % increase, ng/mL

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.