In 1995, researchers Vincent Felitti and Robert Anda began a study that would fundamentally change how we understand the long-term effects of childhood adversity. The ACE Study — Adverse Childhood Experiences Study — surveyed more than 17,000 adults about their childhood experiences and tracked their health outcomes over time.

The findings were striking. Adverse experiences in childhood — abuse, neglect, household dysfunction — were far more common than most people assumed. And their effects, both psychological and physical, were profound and persistent, measurable decades later in mental health, physical illness, and social functioning.

Understanding ACEs does not mean accepting that what happened to you determines who you are. It means understanding a real connection between early experience and later wellbeing — and recognising that this connection can be changed through the right kind of support.

Key Takeaways

ACEs are stressful or traumatic events experienced before the age of 18, including abuse, neglect, and various forms of household dysfunction
The original research identified 10 categories; higher ACE scores correlate with greater risk across a wide range of health and social outcomes
ACEs affect brain development, stress response systems, and attachment — with lifelong consequences if unaddressed
Therapy — particularly trauma-informed approaches — can significantly mitigate the long-term effects of ACEs
Resilience is not merely innate; it is built through relationships, and the therapeutic relationship is one powerful context for this

What Are ACEs?

The original ACE Study measured 10 categories of childhood adversity across three domains:

Abuse:

Physical abuse
Emotional abuse
Sexual abuse

Neglect:

Physical neglect
Emotional neglect

Household dysfunction:

Witnessing domestic violence
Living with a parent who misuses substances
Living with a family member with a serious mental illness
Parental separation or divorce
Having a household member imprisoned

Each category experienced before the age of 18 scores one point. An ACE score of 4 or more was associated in the original study with markedly elevated risks of depression, anxiety, substance use, heart disease, diabetes, and premature death. An ACE score of 6 or more was associated with a 20-year reduction in life expectancy.

These findings have been replicated across different countries, cultures, and populations. The UK version of the study — conducted by Public Health Wales — found that people with 4+ ACEs were more than twice as likely to have poor health, more than three times as likely to have mental health problems, and over seven times as likely to have been involved in violence.

It is important to note that ACE scores are population-level risk indicators, not individual destiny. Many people with high ACE scores do not go on to experience serious difficulties. Protective factors — particularly the presence of at least one stable, warm, consistent caregiver — significantly modify risk. And therapeutic work can build resilience even in adulthood.

How ACEs Affect Development

Understanding why ACEs have such lasting effects requires understanding what happens to a child's developing brain and nervous system under conditions of chronic stress and adversity.

The stress response system. Children are designed to experience stress in the context of a regulated, supportive caregiver who helps co-regulate the stress response. When this fails — when the caregiver is the source of danger, is unavailable, or is themselves overwhelmed — the child's stress system becomes chronically activated. This has lasting effects on the architecture of the brain, particularly structures involved in threat detection (the amygdala), stress response regulation (the prefrontal cortex), and memory (the hippocampus).

Attachment. Early relationships with caregivers form the template for all subsequent relationships. When those early relationships involve fear, inconsistency, or neglect, children develop insecure or disorganised attachment patterns. These patterns — the implicit rules learned about whether others can be trusted and whether the self is worthy of care — persist into adult relationships, often in ways that are not consciously understood.

The developing self. Children who experience chronic adversity often internalise an understanding of themselves as bad, unlovable, or responsible for what happened to them. These core beliefs, formed before the cognitive capacity to challenge them, can persist throughout life as deeply held but unexamined assumptions.

Physiological effects. Chronic toxic stress in childhood affects not just the brain but the immune, hormonal, and cardiovascular systems. This is part of why ACEs correlate with physical health outcomes as well as psychological ones — the long-term activation of the stress response takes a measurable toll on the body.

What This Means in Adult Life

The effects of ACEs may not be visible immediately. Many people with high ACE scores appear to function well — they have careers, relationships, and outwardly successful lives. The effects often surface more subtly: in chronic low-level anxiety, in relationship patterns that repeat, in a persistent sense of unworthiness or emptiness, in difficulty trusting others, in the intensity of reactions to certain situations.

Common manifestations in adult life include:

Chronic anxiety or hypervigilance — a nervous system that never quite settles
Depression and persistent low mood
Difficulty regulating emotions — reactions that feel disproportionate or overwhelming
Relationship difficulties, including difficulties with trust, closeness, conflict, and abandonment fear
A tendency toward people-pleasing or conflict avoidance rooted in early patterns
Substance use or other self-medicating behaviours
Chronic physical symptoms — fatigue, pain, immune difficulties — that resist straightforward medical explanation
A fundamental sense of not being safe, even in objectively safe circumstances

These are not character weaknesses. They are the adaptations of a nervous system and psyche that made the best possible sense given what was experienced.

How Therapy Helps

The good news emerging from decades of research is clear: the effects of ACEs are not fixed. Relationships — with caregivers, peers, partners, and therapists — are the primary medium through which the nervous system and attachment system can be revised. The experience of being genuinely seen, safely held, and consistently responded to by a reliable other can, over time, build the foundations of security that were unavailable in early life.

Trauma-informed therapy is the umbrella term for approaches that understand symptoms as responses to adverse experience rather than as pathology in themselves. A trauma-informed therapist will not approach a client's hypervigilance as a problem to be corrected but as a reasonable adaptation to past danger — one that can gradually be updated as the present becomes distinguishable from the past.

Person-centred therapy creates the relational conditions — empathy, unconditional positive regard, congruence — that are themselves corrective for experiences of inconsistency, criticism, and emotional unavailability. The therapeutic relationship becomes a context in which new relational experiences are possible.

Psychodynamic and attachment-based approaches explore the patterns formed in early relationships and how they repeat in adult life, including in the therapeutic relationship itself. Understanding these patterns — and experiencing them being met differently — allows for genuine revision.

EMDR (Eye Movement Desensitisation and Reprocessing) has a strong evidence base for processing traumatic memories. It works by helping the nervous system reprocess memories that have become "stuck" — held in a form that keeps the past feeling present. Many people with high ACE scores find that specific memories retain a vivid, present-tense quality even decades later; EMDR is often effective for this.

Somatic approaches recognise that trauma is held in the body as well as the mind. Approaches including Somatic Experiencing, sensorimotor psychotherapy, and body-based elements within integrative therapy address the physiological dimension of ACEs — the chronic tension, the startle response, the physical shutdown — in ways that purely verbal therapy may not fully reach.

What to Expect from Therapy for ACEs

Therapy for the effects of adverse childhood experiences is rarely quick. The patterns formed over years of early experience are not dismantled in a handful of sessions. A reasonable expectation is a gradual, non-linear process — with meaningful shifts in self-understanding, relationships, and daily experience developing over months to years.

It is also important to note that the therapeutic relationship itself is part of the work. How the therapist responds when you are distressed, how they repair ruptures in the relationship, whether they are consistent and predictable — these are not just nice features of good therapy. For people whose early relational experience was harmful or absent, they are the primary medium of change.

Finding a therapist who is genuinely trauma-informed, who can work at a pace that feels manageable, and with whom you feel safe enough to explore difficult material, is essential. Do not hesitate to ask potential therapists about their experience working with developmental trauma and ACEs.

Protective Factors and Resilience

The ACE research has tended to generate a significant amount of anxiety when people encounter their own ACE score. It is important to hold this information proportionately.

The presence of one stable, warm, responsive adult in a child's life significantly modifies risk even in the context of high ACE exposure. Stable friendships, school environments, community connections, and faith communities can all serve as partial buffers.

And critically: resilience is not a fixed trait. It is something that develops in the context of relationships. Building the capacity to regulate emotions, to trust others, to understand and articulate one's inner experience, and to connect with others is work that can happen at any stage of life. Therapy is one powerful context in which this happens.

Frequently Asked Questions

Q: I had a difficult childhood but don't feel "traumatised." Do ACEs still apply to me? A: ACEs describe risk, not certainty. You may have significant protective factors that have modified the impact. You may also be experiencing effects you haven't yet recognised as related to early experience. A thoughtful therapist can help you explore what is relevant to your situation without imposing a framework that doesn't fit.

Q: Should I calculate my ACE score? A: ACE scores are useful as population-level research tools. For individuals, they are interesting as a starting point for reflection, but not a clinical tool in themselves. A high score doesn't tell you what you need, and a low score doesn't mean early experience hasn't affected you in other ways.

Q: I've been in therapy before and it didn't help much. What should I do differently? A: This is common among people working with developmental trauma, particularly if previous therapy was relatively short-term or not specifically trauma-informed. It may be worth seeking a therapist with specific experience in this area — and being clear with them about what you found difficult or unhelpful before.

At Kicks Therapy, we work with the long-term effects of difficult childhoods from a trauma-informed, humanistic perspective. Our approach is paced, collaborative, and attuned — recognising that meaningful change in early relational patterns takes time and a genuinely safe therapeutic space.

For a free 15-minute introductory call, contact us today. Sessions in-person in Fulham (SW6), online throughout the UK, and through walking therapy in South West London.

This article is for informational purposes only. For personalised therapeutic support, please consult a qualified mental health professional.

Adverse Childhood Experiences (ACEs): Understanding the Long-Term Impact and How Therapy Helps