What stress does physically
The stress response runs along two axes: the sympathetic nervous system (adrenaline, heart rate, breathing — a reaction in seconds) and the HPA axis (cortisol — a reaction over minutes to hours). Both systems are designed as a short peak followed by recovery.2
If the trigger doesn't go away — financial pressure, conflict, poor sleep, caring for a chronically ill family member — both axes stay elevated. Cortisol, inflammatory proteins and sympathetic activation linger at a background level the body was never designed for. That's allostatic load: the cumulative wear and tear of a system that's 'on' too often, too long.1
Why it matters
Chronic stress is an independent risk factor for cardiovascular disease — comparable in magnitude to classic factors like smoking and high blood pressure.4 It raises blood pressure, shifts the lipid profile unfavourably, disturbs glucose regulation and accelerates atherosclerosis through chronic low-grade inflammation.8
It also disturbs sleep (less deep sleep and REM), suppresses immune function, affects mood and cognition, and is strongly associated with depression and burnout.[3,7] In the short term it feels like 'just busy'; over years it accumulates into concrete medical outcomes.
Acute vs. chronic
Acute stress is healthy. A competitive match, an important presentation or a startle response activates the same systems — but with a clear beginning and end, followed by recovery. That recovery is the physiology working as intended.
Chronic stress is a different animal. The damage comes from duration and missing recovery windows, not intensity. A person with a demanding job who ends every evening with a walk and good sleep is in a better physiological state than someone with less objective pressure but no recovery.[2,7]
What you can measure
The most sensitive indicator is HRV (heart-rate variability), the variation in time between consecutive heartbeats. High HRV reflects good autonomic balance (parasympathetic activity); low HRV is a reliable marker of physiological load and recovery deficit. Wearables (Oura, Whoop, Garmin, Apple Watch) track it precisely enough for week-on-week trends.5
Cortisol can be measured in blood (single moment), saliva (multiple time points to capture the curve) or hair (chronic exposure over weeks–months). A single blood cortisol says relatively little about chronic stress; the timing pattern (morning peak vs. evening pile-up) says more.
Indirect markers that sit in our Baseline and move with chronic stress: hsCRP (low-grade inflammation), HbA1c (chronic cortisol raises insulin resistance), home-measured blood pressure, and cardiovascular markers such as apoB.4
What holds up under research
Sleep is foundational: one bad night measurably shifts HRV and the cortisol curve. Morning daylight, fixed sleep times and a calm evening are the most underrated stress interventions — not because they feel relaxing, but because they keep the physiological clock stable.
For active recovery, breathing techniques (slow, with longer exhales than inhales), regular aerobic and resistance training (lowers baseline cortisol over the long run), and social connection (one of the strongest health predictors in cohort studies) all hold up well. For people wanting more: mindfulness-based stress reduction shows consistent effects on perceived stress, anxiety and depressive symptoms in meta-analyses.6
What makes less difference than people think: cortisol supplements, adaptogens and short 'detoxes'. None of those compensate for structurally poor sleep or a chronically over-stimulated schedule.
When to involve a physician
Book a GP appointment for persistent insomnia, a 'burnt-out' feeling lasting more than a few weeks, panic symptoms, low mood with loss of interest, or unexplained physical complaints (palpitations, breathlessness, stomach problems). Burnout and depression are treatable — earlier intervention shortens recovery time.
At Optimize every blood result also passes through triage. If values that move with stress (HbA1c, lipids, inflammation) fall outside the optimal range, we reach out proactively.