resilience
resilience
The email arrived on a Monday morning, three weeks into a new financial year. Rachel, a Managing Director at a professional services firm, had not taken a sick day in eleven years. She told me this with something that was not quite pride — more like a statement of fact she had stopped questioning. She was fifty-two years old, and she had come to me because she was struggling to concentrate.
Not in meetings. Not on complex problems. She was struggling to concentrate on things she had been doing for twenty years. She described it as "losing the thread" — starting a sentence and finding, somewhere in the middle of it, that she had forgotten where it was going.
Her GP had run every test. Everything was normal. Her coach had suggested she needed better boundaries. Her HR director had recommended a mindfulness app.
None of them had asked her what the last eleven years had actually cost.
The concept of allostatic load was developed by neuroscientist Bruce McEwen and his colleague Eliot Stellar in the early 1990s. It describes the cumulative physiological cost of chronic stress — the wear and tear on the body's regulatory systems that accumulates over time when those systems are repeatedly activated without adequate recovery.
The term builds on the earlier concept of allostasis, which refers to the body's ability to maintain stability through change. When you face a threat — a difficult conversation, a high-stakes presentation, a hostile colleague — your body mobilises resources: cortisol rises, heart rate increases, inflammatory markers activate. This is adaptive.
It is the stress response doing exactly what it is designed to do.
The problem is not the activation. The problem is what happens when the activation never fully resolves.
McEwen's research, conducted over three decades at Rockefeller University, showed that when the stress response is chronically engaged — when the body never returns to baseline — the same systems that protect you in the short term begin to damage you in the long term. The hippocampus, which is central to memory and learning, is particularly vulnerable.
Chronic cortisol exposure causes hippocampal neurons to retract their dendrites, reducing the density of synaptic connections. The prefrontal cortex, which governs executive function, decision-making, and emotional regulation, shows similar degradation under sustained stress load.
Rachel was not experiencing a concentration problem. She was experiencing the neurological consequences of eleven years of unresolved allostatic load.
The research on allostatic load is not gender-neutral.
A series of studies using the MacArthur Research Network's allostatic load index — which measures biological markers including cortisol, blood pressure, waist-to-hip ratio, and inflammatory markers — has consistently found that women in high-demand, low-control occupational environments accumulate allostatic load at higher rates than men in equivalent roles.
There are several mechanisms at work here, and they are worth understanding precisely because they are structural, not personal.
The first is the double-demand burden. Research by Arlie Hochschild at the University of California, Berkeley, established the concept of the "second shift" — the domestic and emotional labour that women continue to perform at disproportionate rates regardless of their professional seniority.
A 2019 study published in the Journal of Marriage and Family found that even in dual-income households where women out-earned their partners, women still performed an average of 65% more domestic labour. This is not a lifestyle choice. It is a structural tax on recovery time.
The second mechanism is the chronic activation of the social threat response. Research by Naomi Eisenberger at UCLA has shown that social exclusion and social threat activate the same neural circuits as physical pain — specifically the dorsal anterior cingulate cortex and the anterior insula.
For women in male-dominated environments, the experience of being evaluated more harshly, interrupted more frequently, and credited less reliably for their contributions is not merely frustrating. It is neurologically costly. Each instance of social threat activates the stress response. When those instances are daily, the activation becomes chronic.
The third mechanism is the suppression of stress expression. Research by James Gross at Stanford on emotion regulation has shown that expressive suppression — the practice of experiencing an emotion but not displaying it — is physiologically more costly than cognitive reappraisal.
Women in senior leadership roles are frequently required to suppress emotional expression in ways that their male counterparts are not. The professional penalty for displaying frustration, anxiety, or distress is higher for women. The result is that the physiological cost of the stress response is incurred, but the behavioural expression that would signal the need for recovery is suppressed.
What makes allostatic load particularly insidious is that it accumulates silently. There is no single event that tips the system over. There is no moment where you can point and say: that is where it happened. Instead, the load builds incrementally — each year of chronic activation adding to the previous one, each period of inadequate recovery compounding the deficit.
McEwen's research identified four distinct patterns of allostatic overload. The first is repeated hits — multiple stressors that prevent the system from returning to baseline. The second is lack of adaptation — the failure to habituate to a repeated stressor, so the response remains as strong on the hundredth exposure as it was on the first.
The third is prolonged response — the inability to shut off the stress response after the stressor has passed. The fourth is inadequate response — a blunted stress response that fails to mobilise sufficient resources, leading to compensatory activation of other systems.
Senior women leaders frequently present with patterns two and three. The social threat environment does not habituate — being interrupted in a meeting on the hundredth occasion still activates the same neural circuits as the first. And the professional context rarely permits the kind of recovery that would allow the stress response to fully resolve.
Rachel's eleven years without a sick day was not evidence of resilience. It was evidence of a system that had never been given the conditions for recovery.
The physiological consequences of chronic allostatic load are measurable. McEwen's index includes markers across four systems: the hypothalamic-pituitary-adrenal axis (cortisol, DHEA-S), the sympathetic nervous system (adrenaline, noradrenaline), the metabolic system (waist-to-hip ratio, blood glucose, cholesterol), and the immune system (C-reactive protein, interleukin-6).
A 2016 study by Theresa Seeman and colleagues at UCLA, following a cohort of high-achieving professional women over a twelve-year period, found that those in high-demand leadership roles showed significantly elevated allostatic load scores compared to matched controls — and that the elevation was not explained by lifestyle factors such as diet, exercise, or sleep alone.
The occupational environment was an independent predictor.
The specific cognitive consequences are well-documented. Elevated cortisol impairs working memory — the ability to hold and manipulate information in real time. It reduces cognitive flexibility — the ability to shift between mental sets and consider alternative perspectives.
It narrows attentional focus, which is adaptive in acute threat situations but counterproductive in the complex, ambiguous environments that senior leadership requires.
This is why Rachel was losing the thread. Her working memory was compromised. Her attentional control was degraded. Her ability to sustain cognitive effort over time had been eroded by years of chronic stress load that had never been adequately resolved.
The research on allostatic load recovery is both more hopeful and more demanding than most people expect.
The hopeful part: the brain is genuinely plastic. McEwen's own research demonstrated that hippocampal dendritic retraction caused by chronic stress is reversible. When the stress load is reduced and recovery conditions are created, the hippocampus begins to rebuild its synaptic architecture. The prefrontal cortex shows similar plasticity.
The brain is not permanently damaged by chronic stress — but it does require specific conditions to recover.
The demanding part: those conditions are not achieved through mindfulness apps or better time management. They require a genuine reduction in allostatic load, which means addressing the structural sources of chronic activation, not just managing the symptoms.
Research by Elissa Epel at the University of California, San Francisco, on telomere length — a biological marker of cellular ageing that is sensitive to chronic stress — has shown that the most effective interventions are those that reduce the objective demands of the environment, not just the subjective experience of stress.
Reframing how you think about a hostile colleague does not reduce the physiological cost of interacting with them daily. Changing the frequency of those interactions does.
This is an uncomfortable finding for an industry that has built a significant business model around teaching people to manage their stress responses better. The evidence suggests that the more important intervention is reducing the load itself.
The practical implications of allostatic load research are specific and actionable, but they require a different framing than the conventional resilience conversation.
The first implication is that recovery is not a luxury — it is a biological requirement. The research on sleep, in particular, is unambiguous.
Matthew Walker's work at the University of California, Berkeley, has shown that sleep is the primary mechanism through which the brain clears the metabolic waste products of cognitive activity, including the cortisol metabolites that accumulate under chronic stress. Reducing sleep to create more productive time is not a trade-off.
It is a direct attack on the cognitive systems that make the productive time valuable.
The second implication is that the sources of allostatic load need to be mapped, not just managed. This means identifying which specific aspects of the occupational environment are generating chronic activation — and being honest about which of those can be changed and which cannot.
The ones that cannot be changed require a different calculation: the cost of remaining in that environment versus the cost of leaving it.
The third implication is that the conventional markers of resilience — the absence of sick days, the ability to sustain high output under pressure, the appearance of coping — are not reliable indicators of biological health. Rachel's eleven years without a sick day was not a sign of resilience. It was a sign that the system had been running without adequate maintenance for a very long time.
The fourth implication is that self-assessment is unreliable under high allostatic load. The same cognitive systems that are degraded by chronic stress — working memory, attentional control, cognitive flexibility — are the systems required to accurately assess one's own cognitive state. This is why the executives who most need to reduce their load are often the least able to recognise it.
One of the most significant problems in this field is the absence of objective measurement. Allostatic load is a biological phenomenon, but most organisations assess it — when they assess it at all — through self-report questionnaires that are subject to exactly the cognitive biases described above.
The Female Leadership Performance Assessment maps eight dimensions of cognitive and neurological functioning that are sensitive to allostatic load: threat reactivity, working memory capacity, attentional control, cognitive flexibility, emotional regulation, recovery capacity, social processing, and executive function. It does not ask how you feel.
It measures how you are actually performing on tasks that require the cognitive systems most vulnerable to chronic stress.
This matters because the gap between subjective experience and objective performance is often largest in the people who most need to know about it. Rachel had no idea how compromised her working memory had become because her reference point for normal had shifted gradually over eleven years. She had adapted to a degraded baseline and called it fine.
She was not fine. She was carrying eleven years of unresolved allostatic load, and the cognitive consequences were finally becoming impossible to ignore.
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