How sharply your cortisol falls through the day tracks your health
Cortisol normally peaks soon after waking and falls away. Across a large pooled body of research, the people whose fall is shallowest had worse mental and physical health.
What the study found
The shape of the daily curve tracks health, not the amount
Cortisol normally peaks soon after waking and falls away through the day. Across a large pooled body of research, the people whose fall is shallowest have worse mental and physical health, with depression, cardiovascular risk and death among the outcomes measured.
The caveat · Illness may flatten the curve first
Every study pooled here watched people rather than assigning anything, so a flat curve may mark illness already underway rather than cause it. The slope was measured differently from study to study, from two saliva samples a day to six or more, which blurs the pooled figure.