When I talk about trauma, mental health, or long-term health problems, I often refer back to something called the Adverse Childhood Experience (ACE) study. This post is here so I can link to it as a simple, go-to explanation of what that actually means.
A Plain-English Guide to the 1998 Felitti Study
In short, the ACE study showed that what happens to us as children, especially painful or chaotic experiences, can have a powerful and measurable impact on our bodies and minds decades later.
What is the ACE study?
Back in 1998, a doctor called Vincent Felitti and a team of researchers looked at the lives of over 9,000 adults in a large health insurance programme in the US.
They wanted to answer a deceptively simple question:
Do difficult or traumatic experiences in childhood increase the chances of health and mental health problems in adulthood?
They weren’t just guessing or asking a few people. They used proper medical records, detailed questionnaires, and statistical analysis on a large group of patients to look for patterns.
The short answer was: yes, and the link is bloody strong.
What counts as an “Adverse Childhood Experience”?
In the study, an Adverse Childhood Experience (ACE) was something significantly harmful or unsettling that happened before the age of 18. They focused on 10 types of experience, grouped into three broad areas:
Abuse
- Physical abuse (being hit, beaten, or harmed).
- Emotional abuse (being constantly insulted, humiliated, or threatened).
- Sexual abuse.
Neglect
- Physical neglect (not having basic physical needs reliably met, like food, hygiene, or medical care).
- Emotional neglect (not feeling loved, supported, or emotionally cared for).
Household difficulties
- Living with a parent or carer who misused alcohol or drugs.
- Living with someone with serious mental illness.
- Witnessing domestic violence, especially towards a mother or female caregiver.
- Having a parent in prison.
- Parents separating or divorcing in a way that caused significant disruption and distress.
Each category counted as one ACE. So if someone experienced emotional abuse, parental alcohol misuse, and domestic violence at home, they’d have an ACE score of 3.
The total score could range from 0 (no ACEs reported) to 10 (all categories present).
How the study worked (without the jargon)
Here’s the basic setup in plain terms:
Thousands of adults taking part in a standard health check were asked confidential questions about their childhood experiences, current health, and habits.
Researchers also had access to their medical records, so they could see real diagnoses, not just what people remembered.
They then compared people’s ACE scores with their adult health outcomes.
They weren’t looking at one single disease. They looked at a wide range of things: depression, addiction, heart disease, lung disease, liver problems, obesity, smoking, risky sexual behaviour, and more.
This matters, because the results weren’t just about “emotional problems” or “being a bit unhappy“. They were seeing clear patterns in serious, sometimes life-threatening conditions.
The big message: ACEs stack up
One of the most important findings was that ACEs behave a bit like cigarettes: the more you have, the greater the risk.
A few key points in normal language:
Many people had at least one ACE. Painful childhood experiences were common, not rare.
The more ACEs someone had, the more likely they were to:
- Struggle with depression, anxiety, or suicidal thoughts.
- Use alcohol or drugs heavily.
- Smoke.
- Become severely overweight.
- Have lots of physical health problems, such as heart disease, chronic lung disease, liver issues, and more.
It wasn’t just a small bump in risk. People with high ACE scores (for example 4 or more) were several times more likely to have serious mental health issues, addiction, or major health conditions compared to people with zero ACEs.
In other words, these weren’t “tiny correlations”. Childhood adversity was showing up as a big, measurable factor in adult health.
Why this matters for how we see people
The ACE study helped shift the way many professionals think. Instead of asking:
“What’s wrong with you?”
we’re encouraged to start asking:
“What happened to you?”
That change in question sounds small, but it’s huge.
It reminds us that:
A lot of “bad habits” in adulthood (smoking, drinking, overeating, risky sex) can be coping strategies learned after early trauma.
Chronic illnesses aren’t always random or purely genetic. Long-term stress and trauma can wear down the body over time.
Shame and self-blame often sit on top of experiences that weren’t someone’s fault in the first place.
The study doesn’t say that everyone with ACEs is doomed, or that childhood explains everything. It simply shows that these early experiences matter far more than people used to think, and that ignoring them is a bit like ignoring a broken leg and only giving someone painkillers.
Common misunderstandings
A few things are worth clearing up, because the ACE idea has become quite popular and sometimes gets oversimplified.
An ACE score is not a diagnosis. It’s a rough risk indicator, not a label. A high score doesn’t mean you will get ill, and a low score doesn’t mean you’re fine.
Not all adversity is captured by the original 10 questions. Things like bullying, poverty, racism, medical trauma, and school pressure can also have deep effects, even if they’re not in the classic ACE checklist.
Resilience matters. Supportive adults, safe relationships, therapy, community, and stability can all buffer or reduce the impact of ACEs. Human beings are not machines; context and support make a huge difference.
It’s about patterns, not destiny. The study talks in terms of probabilities at a population level. It doesn’t predict any one person’s future.
So what do we do with this information?
If you recognise yourself in any of this, a few gentle takeaways:
Your struggles might make more sense than you realise. If you grew up in chaos or fear, and you’re living with mental health issues, addiction, chronic pain, or health conditions, you’re not “weak” or “broken”. Your body and brain may be responding to long-term stress you never chose.
Support is not a luxury. Therapy, safe relationships, boundaries, rest, and medical care are not indulgences. They are part of repairing long-term wear and tear.
It’s never “too late” to understand. Many people discover the ACE framework later in life and feel a mix of relief, anger, and sadness. All of that is valid. Making sense of the past can be a powerful step towards change in the present.
What does an ACE score actually mean?
If you’ve just taken an online ACE test and got a high number staring back at you, take a breath. Here’s what it means, and what it doesn’t.
A score of 4 or more suggests you lived through a high level of childhood adversity. Research links this to increased risks for mental and physical health problems in adulthood, on average, but it doesn’t decide your future. It’s a sign your history deserves to be taken seriously, not a life sentence.
A score of 6 or more usually reflects very significant adversity growing up. Statistically, people in this group show higher rates of chronic illness, depression, addiction, and earlier death. That’s why trauma-informed support and genuine care matter so much.
But here’s where most online ACE tests fall short.
They jump from “You scored 6” straight to “you’re at risk of X per cent more whatever”, without holding the emotional weight of what that number actually represents. Six different types of bad things happened to you before you were 18. Of course your system is on high alert. Of course you developed coping strategies. That’s not a character flaw. That’s survival.
The useful bit of an ACE score is not to scare you. It’s to:
Validate what you already feel. No wonder it’s been hard, given what you went through. Your reactions aren’t irrational. They make sense.
Inform your care. GPs, therapists, or psychiatrists can take stress-related illness, chronic pain, or coping behaviours more seriously when they understand your history. A number on a screen isn’t a diagnosis, but it can open a conversation that actually helps.
If you’ve just taken one of these tests and you’re sitting with a big number and a knot in your stomach, don’t let a website turn your childhood into a risk percentage. Talk to someone. A GP (and if they don’t seem familiar with ACEs, ask for a referral to someone who is), a counsellor, a trusted friend.
The score tells you where you’ve been. It doesn’t get to tell you where you’re going.
How I use the ACE study in my writing
When I mention ACEs or the Felitti study in other posts, I’m usually doing one of a few things:
- Pointing out that early experiences can echo through adulthood in ways we don’t always notice.
- Challenging the idea that people’s problems are just about “willpower” or “bad choices”.
- Encouraging kinder, more trauma-aware views of ourselves and others.
If you see a link to this page in another article, it’s here so you can explore the background in one place, in plain language, without needing a medical journal or a psychology degree.
ACE Tests – Your Questions Answered
What is the ACE study in simple terms?
The ACE study was a large-scale research project from 1998 that looked at how difficult childhood experiences affect adult health. It found that the more adverse experiences someone had before the age of 18, the higher their risk of serious physical and mental health problems later in life.
What does ACE stand for?
ACE stands for Adverse Childhood Experience. It refers to specific types of abuse, neglect, and household difficulties that happen before the age of 18. The original study identified 10 categories, and each one counts as one point on the ACE score.
What is an ACE score and what does it mean?
An ACE score is a number from 0 to 10 based on how many types of adverse childhood experience someone reports. It’s a rough risk indicator, not a diagnosis. A higher score is linked to greater risk of health and mental health problems, but it doesn’t predict any individual’s future.
Can you recover from a high ACE score?
Yes. A high ACE score increases risk, but it doesn’t determine your outcome. Supportive relationships, therapy, community, and stable environments can all reduce the long-term impact of childhood adversity. Resilience is real, and it’s never too late to seek support.
Does the ACE study only apply to mental health?
No. One of the study’s most striking findings was that childhood adversity is linked to serious physical health conditions too, including heart disease, chronic lung disease, liver problems, and obesity. The effects go well beyond emotional wellbeing.