By any measure, the results are one of the most important public health findings of the last century. The relationship between ACE score and adult health outcomes was dose-dependent, powerful, and remarkably consistent across conditions: the more adverse childhood experiences reported, the higher the risk of heart disease, diabetes, stroke, cancer, chronic lung disease, liver disease, depression, anxiety, attempted suicide, alcoholism, drug abuse, early death. A person with four or more ACEs was twice as likely to have heart disease, twelve times more likely to attempt suicide, seven times more likely to struggle with alcoholism. Not a subtle gradient. Massive.
Nadine Burke Harris is a pediatrician who ran into the ACEs research as a young clinician at a San Francisco community health clinic, recognized what it meant for her patients, and built a career translating it out of the research literature and into clinical practice. The Deepest Well, published in 2018, is her accessible account of what the ACEs research means, how adversity gets biologically embedded in developing bodies, and what medicine and society should be doing about it. Burke Harris became California’s first Surgeon General in 2019 partly on the strength of this work. The book earns the attention.
The ACEs Research: The Core Findings
Worth stating the ACEs findings precisely, because they get misread constantly, in both directions — overdramatized, or waved off. The ACE score is not destiny. A high ACE score doesn’t mean heart disease or addiction or an early death is coming. It means the statistical risk of those outcomes is substantially elevated. Risk isn’t fate. Understanding risk is where you start addressing it — not a sentence being handed down.
What makes the findings compelling isn’t just the magnitude. It’s the consistency and the biological plausibility. The relationship holds across income levels, racial groups, regions. It holds for physical health outcomes — not only the mental health and behavioral outcomes one might expect from childhood adversity — in a way that demands a biological explanation. Childhood stress doesn’t just leave psychological trauma behind. It changes physiology.
Burke Harris explains the mechanism through what she calls “toxic stress” — activation of the stress response systems (HPA axis, sympathetic nervous system, immune function) in a way that’s severe, prolonged, or repetitive, without enough adult buffering to soften it. Normal stress — what researchers call “positive” or “tolerable” stress — is part of healthy development. The HPA axis activates, cortisol rises, the body mobilizes resources, the stressor resolves, the system returns to baseline. That’s a healthy stress response, calibrated correctly.
Toxic stress is what happens when the stressor overwhelms, or won’t stop, or keeps repeating, and the child doesn’t have adequate adult support to buffer the physiological hit. Under those conditions the stress system activates over and over, severely, without returning to baseline in between. Over time that produces an altered calibration — the HPA axis stays activated even without a present threat, or gets dysregulated toward either hyperreactivity or hyporesponsiveness. That altered calibration is the mechanism through which childhood adversity gets embedded in biology, not just psychology, and produces the long-term health consequences the ACEs research documents.
Biological Embedding: How Stress Gets Under the Skin
One of the most important and most complicated sections of The Deepest Well covers exactly how adversity gets biologically embedded in developing bodies. Burke Harris walks through three mechanisms: HPA axis dysregulation, immune system alterations, and epigenetic changes.
The HPA axis — hypothalamic-pituitary-adrenal — is the body’s primary hormonal stress response system. Under toxic stress in childhood, its calibration can get altered in ways that persist into adulthood: set point too high (chronic cortisol elevation, hyperarousal, anxiety), or burned out and set too low (blunted cortisol response, chronic fatigue, depression). These alterations touch nearly every system cortisol regulates — which is most of them — cardiovascular function, immune response, metabolic function, brain development.
The immune system alterations matter enormously for understanding the physical health outcomes. Chronic activation of inflammatory pathways, which happens under sustained stress, produces the low-grade chronic inflammation now understood to sit underneath heart disease, diabetes, certain cancers, and other leading causes of premature death. The pathway from childhood adversity to adult heart disease runs, at least partly, through chronic immune activation that produces atherosclerosis and other inflammatory conditions. Not a metaphor. A measurable biological mechanism.
The epigenetic changes are the most scientifically contested of the three, and potentially the most significant. Epigenetics concerns changes in gene expression — which genes get switched on or off — rather than changes to the underlying DNA sequence itself. Emerging evidence suggests sustained toxic stress can produce lasting epigenetic modifications that alter the expression of stress response genes, and in some cases those modifications appear to pass to the next generation. This is the biological mechanism behind what’s been called intergenerational trauma — the observation that the physiological consequences of adversity can travel to children and grandchildren.
The epigenetic transmission evidence is real, but it’s considerably more complex and preliminary than the popular presentations usually let on. The mechanisms are mostly established in animal models, and the human evidence is mostly correlational. What can be said with confidence: the physiological effects of adversity are biological, heritable in some sense through the behavioral and parenting effects on the next generation’s stress calibration, and potentially — in at least some cases and species — transmissible through epigenetic mechanisms that don’t require any learning or behavioral transmission at all.
The Dose-Response Relationship: Understanding Your ACE Score
The dose-response relationship — health risk climbing with ACE score in a roughly graded way — is one of the study’s most important features from a clinical and practical standpoint. ACEs aren’t all-or-nothing in what they mean for health. Each increment of adversity is an increment of risk that can be assessed, addressed, and, to a degree, mitigated.
Burke Harris is careful to note that the ACE score is a research tool, not a clinical diagnostic. The ten items in the original study aren’t the only relevant adversities out there — they’re the ones that specific study measured in that specific population. Community violence, racism, poverty, natural disasters, medical trauma, and plenty of other adversities never made it into the original ACE score. A person scoring low on the original scale may well have taken on significant adversity in domains the scale simply doesn’t touch.
What the ACE score usefully communicates — to individuals and to clinicians — is the concept of cumulative adversity burden. Each adverse experience isn’t just an independent risk factor sitting on its own. They interact. They compound. A child living through physical abuse and household substance abuse and parental divorce hasn’t experienced three independent risks. They’ve experienced an environment of chronic toxic stress in which multiple adversity sources keep the stress response system persistently activated. It’s the cumulative activation pattern, not any single event, driving the biological embedding.
“Toxic stress is like living with the smoke alarm constantly going off. There’s always a reaction, always a heightened state of alert, always preparation for fight, flight, or freeze — even when there’s no emergency.” Burke Harris on the physiological experience of the chronically activated stress response. The alarm that can’t turn off doesn’t just produce psychological distress. It wears out the systems it was meant to protect.
The Clinical Response: What Doctors Should Do
The screening argument is compelling on its face: if childhood adversity is a risk factor for adult disease on the order of smoking or obesity, medicine should be assessing it with the same systematic attention it gives smoking and obesity. The current practice of simply not asking about childhood adversity in clinical settings means a major determinant of health outcomes is being systematically ignored. Burke Harris’s own clinic in San Francisco started systematically screening for ACEs and found that most patients had at least one, and a significant share had four or more — the level the research ties to dramatically elevated risk.
The treatment framework she built — “healthy outcomes from positive experiences” (HOPE), alongside attention to sleep, exercise, nutrition, mindfulness, mental health support, and healthy relationships — is essentially an attempt to counteract the biological mechanisms of toxic stress using interventions already known to support HPA axis regulation, immune function, nervous system health. Not magic. The application of known biological mechanisms to a known biological problem.
The broader public health argument — that society should invest in preventing adverse childhood experiences through family support systems, economic stability, quality childcare, and treatment for parental mental health and substance use — is straightforward from a cost-benefit standpoint. The health and social costs of treating the adult consequences of childhood adversity are enormous. The cost of preventing that adversity through early intervention is a fraction of that. Not a liberal argument or a conservative one. Arithmetic. Whether society acts on the arithmetic is political. The arithmetic itself isn’t.
The Protective Factor Research: What Mitigates ACEs
One of the most practically important sections of The Deepest Well — and the most underemphasized in popular coverage of the ACEs research — is about protective factors: the things that buffer the biological impact of adversity and keep ACEs from fully converting into the health outcomes the research predicts.
The most consistently identified protective factor is the presence of at least one stable, caring adult relationship. This finding holds up across the entire adversity literature: children with even one adult offering consistent, warm, responsive care — a parent, a grandparent, a teacher, a coach, a neighbor — show substantially better outcomes across every domain than children facing comparable adversity without that relationship. It doesn’t need to be perfect. It needs to be present, warm, responsive, consistent. Co-regulation — an adult’s regulated nervous system helping stabilize a child’s dysregulated one — is the primary mechanism at work.
Other protective factors: community connectedness (support networks beyond the immediate family), physical health behaviors (exercise, sleep, nutrition), a sense of control and agency over one’s circumstances, and access to mental health support. None of these erase the biological effects of adversity — the stress systems still fire, the epigenetic effects still happen — but they provide regulatory resources that support the return to baseline after activation, and build the resilience capacity that lets the system recover from adversity without settling into permanent dysregulation.
This matters for anyone with a high ACE score who might read the research as a biological death sentence. It isn’t one. Biology isn’t destiny. The protective factors are real and reachable. Building the regulatory infrastructure — exercise, sleep, social connection, mindfulness, and often professional mental health support — is the response the research actually supports for elevated ACE scores. The biological embedding is real. The biological responsiveness to protective interventions is equally real.
The Proprietary Framework: The ACE-Response Protocol
For readers wanting to act on their own ACE scores, or the ones they recognize somewhere in their history, here’s a framework built on the evidence around biological impact and protective factors:
- Assess and acknowledge without catastrophizing. Calculate the ACE score using the original scale (publicly available). Know the number. Acknowledge what it represents — not a sentence, a risk profile that warrants attention. A high ACE score means more watchfulness around the specific outcomes the research ties to it, and more investment in the protective factors that mitigate them. It does not mean broken or doomed.
- Prioritize sleep as a biological imperative. Sleep is the single most powerful intervention available for HPA axis regulation and immune function, and it doesn’t require a prescription. Chronic sleep deprivation worsens stress system dysregulation and speeds up the health consequences of toxic stress. Treating sleep as non-negotiable — not the first thing sacrificed under pressure — is among the highest-use health behaviors for anyone with an adversity history.
- Exercise as stress system regulation. Aerobic exercise has documented effects on HPA axis function, inflammatory markers, and stress resilience. For people with high ACE scores it isn’t adjunctive. It’s primary. Burke Harris recommends it explicitly as a biological counterweight to the dysregulation adversity produces.
- Build and maintain stable adult relationships deliberately. The protective effect of stable, caring adult relationships doesn’t expire at eighteen. Adults with adversity histories benefit from the same co-regulatory function of close relationships — the stabilizing pull of someone else’s regulated nervous system on their own. Building and maintaining these is a health behavior. Not a luxury.
- Address sleep, exercise, nutrition, substance use, and mental health as one integrated system. Burke Harris’s HOPE framework treats these as interconnected — improve one, the others tend to follow; neglect one, the others suffer. The goal isn’t perfection in any single domain. It’s adequate function across all of them at once.
The Verdict on The Deepest Well
The Deepest Well is an accessible, well-written account of one of the most important bodies of public health research from the past thirty years. Burke Harris is a gifted communicator who makes the ACEs science comprehensible without dumbing it down, and her clinical experience grounds it all in actual patient reality. The book matters both as a personal framework for adults with adversity histories and as a public health argument for changing policy in healthcare, education, and family support systems.
The limitations are contained. This is advocacy as much as pure science communication, which means the uncertainty in some areas — epigenetic transmission particularly — gets somewhat underplayed relative to what the research actually supports right now. The policy prescriptions are sensible but run into real implementation barriers the book doesn’t fully wrestle with. Minor qualifications on a genuinely important contribution.
Read it with a high ACE score, wanting to understand what it means biologically and what’s actually doable about it. Read it working with children or families. Read it as a healthcare provider who hasn’t yet built adversity screening into practice. The arithmetic is clear. The health consequences of childhood adversity are real, biological, and addressable. The open question is whether the research gets taken seriously enough to act on.
Deepest Well Summary: Your Questions Answered
- What are ACEs? Adverse Childhood Experiences — ten categories of childhood adversity assessed in the landmark CDC-Kaiser study: physical abuse, sexual abuse, emotional abuse, physical neglect, emotional neglect, witnessing domestic violence, household substance abuse, household mental illness, parental separation or divorce, and having a family member imprisoned. The ACE score is the number of these categories a person reports experiencing before age 18.
- What does a high ACE score mean for my health? Statistical risk elevation, not certainty. A score of 4 or more is associated with roughly double the risk of heart disease, 12 times the risk of suicide attempt, 7 times the risk of alcoholism, and elevated risk of numerous other physical and mental health conditions. These are population-level risk elevations, not individual destinies. Many people with high ACE scores live long, healthy lives; many with low scores develop serious illness. The score identifies elevated risk warranting attention and the deployment of protective factors.
- What is toxic stress? Burke Harris’s term for the stress response activation that occurs when adversity is severe, prolonged, or repetitive without adequate adult buffering — producing chronic or repeated activation of the HPA axis and stress response systems without adequate return to baseline. Distinguished from positive stress (normal development-supporting stress) and tolerable stress (significant but time-limited stress with adequate support). Toxic stress produces biological alterations that underlie the long-term health consequences documented in ACEs research.
- How does childhood adversity affect the brain? Multiple mechanisms: altered HPA axis calibration (the stress hormone system), changes to the architecture of the hippocampus (memory and context processing), amygdala hypersensitivity (threat detection), reduced prefrontal cortex development and connectivity (executive function, emotional regulation), and altered dopamine and reward system function. These changes affect learning, emotional regulation, attention, impulse control, and threat sensitivity in ways that are measurable and that partially underlie both mental health and behavioral outcomes associated with high ACE scores.
- Can the biological effects of ACEs be reversed? Partially and progressively. Biology is not destiny. The stress system changes produced by adversity are responsive to the protective factors that the research identifies: stable caring relationships, adequate sleep, regular exercise, good nutrition, mindfulness practices, and mental health support. These don’t erase the biological history but they do alter the ongoing calibration of stress systems in meaningful ways. The brain and body retain significant plasticity throughout the lifespan — change is possible, though slower for some dimensions than others.
- Should doctors screen for ACEs? Burke Harris argues yes, systematically and routinely, and this position has been gaining clinical traction. California mandated ACE screening in Medicaid-enrolled patients in 2020 following Burke Harris’s work as Surgeon General. The argument is straightforward: if ACE score is a major determinant of health outcomes, medicine should assess it with the same systematic attention given to other major risk factors. Screening without adequate treatment protocols is insufficient, but it’s the necessary first step toward appropriate clinical response.
- Is the epigenetic transmission of ACEs real? The evidence for epigenetic transmission of adversity effects — the idea that the biological consequences of your grandparents’ adversity are partly transmitted to you through changes in gene expression rather than through behavioral or psychological mechanisms — is real but more preliminary in humans than popular accounts often suggest. Animal models show clear epigenetic transmission. Human evidence is correlational and the mechanisms are less well-established. What can be said: behavioral and parenting mechanisms of intergenerational transmission are well-established. Epigenetic mechanisms in humans are plausible but not yet definitively proven.
- What is the most important protective factor against ACE effects? Consistently, across the adversity literature: the presence of at least one stable, caring adult relationship. This relationship doesn’t need to be a parent — a grandparent, teacher, coach, or community adult can provide the co-regulatory function that buffers stress system activation in children with adversity. In adults, the equivalent is sustained, warm, reliable close relationships that provide co-regulation and social support. The protective factor doesn’t disappear at age 18; it remains relevant throughout the lifespan.
- How does this research relate to mental health treatment? Significantly. Burke Harris argues that mental health treatment for people with high ACE scores should be informed by the biological embedding of adversity — not just addressing symptoms but addressing the underlying stress system dysregulation. This means treatment that incorporates sleep, exercise, and other biological protective factors alongside standard psychotherapy, and that uses trauma-informed approaches that understand why ACE-related symptoms present the way they do. The mental health resources at Resilient Wisdom provide accessible frameworks for building the regulatory capacity that adversity histories often require. For understanding the broader resilience landscape and the specific tools for developing the growth mindset that transforms adversity into forward movement, the Resilient Wisdom toolkit provides complementary practical pathways.
- What policy changes would most reduce ACEs? Burke Harris advocates for: economic stability for families with young children (poverty is strongly correlated with ACE exposure), universal high-quality early childhood education and childcare, treatment of parental mental health and substance use (many ACEs are downstream effects of untreated parental struggles), and family support programs that reduce family stress during the early childhood period. The cost-benefit analysis strongly favors early investment — the costs of treating adult consequences of childhood adversity substantially exceed the costs of preventing that adversity through early support systems.
The Deepest Well makes the case that childhood adversity is a public health problem of the first order — not a social work concern, not a mental health specialty, but a core driver of the leading causes of premature death and disability that medicine has substantially failed to address. Burke Harris’s career has been the attempt to change that. The research is there. The mechanisms are understood. The protective factors are known and deployable. For readers with adversity histories, the Resilient Wisdom resilience framework, the emotional regulation tools, and the mental health resources offer practical pathways toward the protective factors the research identifies as meaningful.
The Intergenerational Transmission: Beyond Epigenetics
The most powerful intergenerational mechanism is the well-documented effect of adversity on parenting. Adults with high ACE scores have, on average, more trouble with emotional regulation, higher rates of substance use and mental health problems, greater economic instability, and rougher relationship patterns. Each of these shapes the parenting environment in ways that raise the odds a child gets exposed to the same adversity categories the parent lived through. The child of a parent whose own childhood involved household substance use is more likely to grow up in a household with substance use — not primarily through genetics or epigenetics, but through the behavioral fallout of untreated parental trauma.
This mechanism is both sobering and actionable. Sobering, because it explains why poverty and adversity get transmitted across generations so reliably even without any genetic or epigenetic mechanism at all — the environmental conditions producing adversity tend to persist, and to reproduce themselves. Actionable, because it names the intervention point: treating parental mental health and substance use, giving families with young children real economic stability, offering parenting support that rebuilds capacities adversity may have compromised — all effective ways to break the cycle.
Burke Harris is direct about this: healing your own adversity history is itself an ACE-prevention intervention for your children. When adults with high ACE scores build regulatory capacity, address mental health needs, maintain sobriety, and develop stable relationship patterns, they change the environment their children grow up in. The intergenerational transmission is real and powerful. So is the intergenerational healing. The work done on your own nervous system, your own attachment patterns, your own stress calibration — that work isn’t only for you. It is, in a very literal sense, a gift to whoever comes after.
The emotional resilience work at Resilient Wisdom is relevant here not just as individual wellbeing practice but as a multigenerational project. A parent who builds genuine regulatory capacity and models shame resilience, stress tolerance, and effective relationship repair is handing their children protective factors the research names among the most powerful available. The deepest well of the title is the source of adversity that gets passed down. But wells can be capped. New ones can be dug. The work is worth doing for everyone downstream of you, not just for yourself.
Community-Level Adversity: Beyond Individual Scores
One important limitation of the original ACE score — which The Deepest Well acknowledges and partly addresses — is its individual focus. The score measures adversity inside the immediate family. It doesn’t directly capture community-level adversity: neighborhood violence, community poverty, school quality, environmental toxins, systemic discrimination, and the accumulated stress of living somewhere under chronic economic and social distress.
Research since the original Felitti and Anda study has widened the adversity concept to include these community-level factors, and the findings line up: community adversity produces the same biological embedding as family adversity. Kids growing up in neighborhoods with high rates of violence, concentrated poverty, and community distress show elevated stress biomarkers comparable to kids facing family-level adversity. The stress response system doesn’t distinguish between a threat at home and a threat out on the street.
Real implications here, for both public health policy and individual self-understanding. For policy: reducing community adversity — economic investment in high-poverty communities, violence reduction, environmental cleanup, educational equity — is ACE prevention at scale. For individuals: growing up in a community under sustained stress means the original scale’s ACE score is likely undercounting the real adversity burden. The biological consequences probably track the total adversity experienced, not just the family-level slice the standard scale captures.
Burke Harris’s public health work as California’s Surgeon General took this on directly, pushing ACE screening and response across healthcare, education, and social service systems in ways that recognize community-level adversity alongside family-level adversity. The goal is a comprehensive public health response to the full adversity burden children carry, not just the slice that fits neatly on a ten-item checklist. Anyone thinking through their own history in these terms should be asking not just “what happened in my household” but “what was the total adversity environment my stress response system actually developed inside of?” That’s the honest question worth sitting with.
Hope as Science: The Recovery Research
Despite the sobering weight of most of the ACEs research, The Deepest Well ends up an optimistic book — grounded in the evidence for recovery and protective factors rather than resting on the documentation of damage. Burke Harris chose the acronym HOPE (Healthy Outcomes from Positive Experiences) for her clinical framework on purpose: the research on protective factors and recovery is every bit as strong as the research on adversity’s effects, and it deserves equal weight in any honest account of what the science actually shows.
The positive experience research — developed mainly by Robert Sege, Jack Shonkoff, and colleagues at Harvard’s Center on the Developing Child — identifies four categories of experience that build resilience against adversity effects: safe, stable, nurturing relationships; opportunities to develop social and emotional competencies; economic stability; and community belonging. Not soft aspirations. The behavioral and environmental mirror image of the adversity factors in the ACE score, identified through the same epidemiological methods, with measurable protective effects on the same biological outcomes adversity elevates.
The science of hope, in short: the developing brain — and, to a lesser but still meaningful degree, the adult brain — responds to positive experience in ways that can partially counteract and continue to mitigate adversity’s biological effects. Not a claim that positive thinking cures trauma. A claim that the same neural plasticity letting adversity alter biological development also lets protective experience alter it back the other way. The body that kept the score of harm can also keep the score of care. Both accounts get written in the same biological ink, and the ledger stays open.
For readers with high ACE scores, the HOPE research offers a practical program: deliberately build the positive experience categories into daily life. Invest in stable, nurturing relationships — with partners, friends, community, mental health professionals. Develop emotional competencies through deliberate practice. Build economic stability as a health intervention, not merely a financial goal. Connect to community in ways that provide genuine belonging. None of this is adjunctive nicety. By the evidence, these are the most powerful interventions available to people whose early biological setpoints were calibrated by adversity. The resilience toolkit and the emotional regulation resources at Resilient Wisdom provide practical frameworks for building the competencies the HOPE research identifies as protective.
The Medical System Response: Still Catching Up
One of the more frustrating realities The Deepest Well documents is the gap between what the ACEs research shows and what the medical system actually does about it. The findings have been available since the late 1990s and rank among the most replicated in epidemiology, and yet routine ACE screening in medical settings remains uncommon more than two decades later. Primary care physicians still rarely ask about childhood adversity. The biological embedding mechanisms aren’t taught in most medical training. The treatment protocols that would address toxic stress as a clinical finding are not standard of care.
Burke Harris’s work as California’s Surgeon General is one of the most systematic attempts to change this — building screening into the Medicaid system, training providers, developing treatment protocols. Real progress. Also slow, relative to the scale of the problem. The gap between evidence and practice isn’t unusual in medicine — adoption lag for major clinical innovations often runs decades — but it’s particularly frustrating given the size of the health burden the ACEs research documents.
For anyone navigating this gap, the practical implication is plain: the current healthcare system cannot be relied on to routinely address an adversity history. Bringing the research to your own providers, advocating for adversity-informed care, being proactive about the protective interventions the research supports — that may all fall on you. An unfair burden to hand someone who’s already carried significant adversity. Also, given where medical practice currently stands, the realistic situation. The science is ahead of the system. Until the system catches up, people with high ACE scores who understand the research are better positioned to advocate for themselves and get to the resources that genuinely help than people who don’t. That’s the practical value of the book: it hands over the information to be an informed advocate for your own health inside a system still learning to ask the right questions.
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