Is Cortisol useful for longevity?

Cortisol is an essential stress hormone that is acutely vital for survival. However, chronically elevated levels are well-documented to accelerate aging processes (e.g., telomere shortening, immune suppression, insulin resistance). Therefore, cortisol itself is not 'useful' for longevity; rather, healthy stress regulation is key. Practices like meditation, sleep hygiene, and exercise sustainably lower cortisol. Measuring cortisol (saliva, blood) can help identify chronic stress, but as a standalone biomarker for longevity it is insufficient. The evidence is moderate: strong associations exist between chronic stress and premature aging, but no randomized trials prove that lowering cortisol extends lifespan. Caution: 'cortisol blockers' or supplements may disrupt adrenal function.