Adverse childhood experiences (“ACEs”): What are they, and how much harm do they cause?

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Adverse childhood experiences, also known as ACEs, are early life events that can trigger toxic stress or trauma. They are quite common, and put kids at increased risk for a variety of bad health outcomes. But not all ACEs are equally harmful, and exposure doesn’t mean that an individual is doomed.

Social scientists call them “adverse childhood experiences” (or “ACEs”), and they include some of the most intense, early life stressors: emotional, physical, or sexual abuse; neglect; witnessing domestic violence; suffering the loss (death) of a parent;  living through parental divorce or separation;  having a parent who has been imprisoned; sharing a home with someone who is a substance abuser, or who is depressed, suicidal, or mentally ill.

Is this a complete list? No. The point of labeling something as an ACE is to identify a situation that can trigger toxic stress or trauma. And — unfortunately — there are many possible ways for a child to be stressed or traumatized. So researchers have proposed additional sources of early life adversity, including family financial hardship, residential instability, and living with a household member who is seriously ill or disabled (Zhang et al 2021; Nobari and Whaley 2021; Manyema et al 2018). Other ACEs include bullying, race-based discrimination, and exposure to neighborhood violence or warfare (Bethel et al 2017; Lin et al 2021; World Health Organization 2018).

Do adverse childhood experiences predict poor health outcomes?

Yes. Ever since Vincent Felitti and his colleagues first proposed the ACE concept, researchers have documented correlations between early life adversity and worsened health outcomes.  Initially, Felliti’s team confined themselves to a list of seven major ACEs (Felitti et al 1998):

  • psychological abuse
  • physical abuse
  • sexual abuse
  • living with household domestic violence
  • living with household members who are substance abusers
  • living with household members who are mentally ill or suicidal
  • living with household members who were (at any point in life) imprisoned

But subsequent studies expanded this list of ACEs to include things like child neglect, serious family financial difficulties, and parental divorce or separation. And the general approach has been pretty consistent: Get a sample of individuals living in the real world, and find out about their early life experiences and subsequent health. Then perform statistical analyses to see if people with ACEs are more likely to suffer worse health outcomes over time.

What happens?  Again and again, researchers see the same links. Kids with ACEs are at higher risk for developing psychological problems, substance abuse problems, and physical health conditions.

For instance, in a review of 23 studies conducted in North America and Europe (Bellis et al 2019), researchers found that people who grew up with just one ACE had a 30-50% higher risk of experiencing depression. They were also 23-29% more likely to smoke, and around 50% more likely abuse alcohol or drugs. And folks with two ACEs or more?  Compared with individuals without any ACEs, they had at least double the risk of

  • depression,
  • anxiety,
  • harmful alcohol use,
  • illicit drug use, and
  • respiratory disease.

In another analysis of data collected in Europe, researchers found that individuals with two or more ACEs were about 75% more likely to experience a stroke, and they were approximately 50% more likely to suffer from cardiovascular disease, diabetes, and cancer. People with two or more ACEs were nearly four times as likely to be involved in an act of interpersonal violence (Hughes et al 2021).

So ACEs have been linked with substantially higher rates of psychological and physical health problems. There is also evidence linking ACEs with specific physiological changes, including

  • altered DNA methylation, which can turn important genes “on” or “off”;
  • shortened telomeres (a condition that puts individuals at risk for DNA damage and premature aging); and
  • modified brain development  (which is associated with cognitive and behavior problems).

For more about these physiological changes, see my article “How toxic stress affects brain development.”

Are all ACEs equally harmful?

How children respond to ACEs depends on many things, including their own prior history, genetic risk factors, and what kinds of social support they receive. And of course the ACE categories themselves are a bit fuzzy. Two people might both have a history of parental divorce, yet have experienced very different levels of adversity as a result. It depends on the details.

But, generally speaking, parental divorce isn’t as detrimental as abuse or neglect. And there’s evidence that one form of abuse — sexual abuse — is especially damaging, particularly if it co-occurs with another ACE (Briggs et al 2021).

Can ACEs shorten a person’s life span?

It looks that way. When researchers compare long-term outcomes among people who experienced different levels of early life adversity, they often find that ACEs are predictive of shorter life spans.

For example, in a British study of more than 7000 individuals born in 1958, men had a 57% higher chance of dying by age 50 if they grew up with 2 or more ACEs. Among women, individuals with a single ACE had a 66% increased risk of death. Women with two or more ACES had an 80% increased risk (Kelly-Irving et al 2013).

How can we be sure that it was childhood adversity that was responsible for higher death rates, and not adversity experienced at another time of life?

It’s tricky because some people start out with disadvantages that begin before birth. And of course it’s not unusual for folks to experience adversity during adulthood, or to engage in adult behaviors that increase their risk of disease. So when an adult dies at relatively young age, how do we tease apart causation? How much of the life span was shortened by childhood adversity, and how much by prenatal or adult adversity?

To address this question, researchers in the British study used statistical methods to control for a variety of confounding factors — including prenatal exposure to cigarette smoke, adult socioeconomic status, and several health-relevant characteristics measured at age 23 (BMI, tobacco use, alcohol use, and symptoms of depression or anxiety). The heightened mortality numbers they came up with (57% greater chance of dying for men, and 80% greater chance of dying for women) reflected the effects of childhood adversity after taking these confounding factors into account.

That’s interesting, especially given that many of those health-relevant characteristics at age 23 could themselves have been caused by ACEs. Childhood adversity had a powerful effect on adult mortality, even after researchers controlled for adult behavior problems associated with early life stress.

But how does adversity translate into bad health? What’s the physiological connection between early life stress and the development of disease or pathology?

There are a number of pathways. When adversity keeps triggering a child’s stress response system, the body gets exposed to chronically high levels of stress hormones. This can cause elevated blood pressure, high blood sugar, and inflammation — leading to a variety of diseases.

In addition, stress can effectively turn genes “on” and “off,”  which alters the levels of different proteins, hormones, and neurotransmitters in the brain.  And these changes in brain chemistry can lead to abnormal patterns of brain development — with negative consequences for mental health, social adjustment, and cognition.

So it makes sense that ACEs are linked with poor health outcomes, but we still have to be mindful of the limitations of correlational studies. ACEs might cause early mortality because they overactivate an individual’s stress response system, as we’ve just noted. But it’s also possible that something else — something that researchers aren’t measuring — is playing a role.

For instance, when researchers evaluate an individual’s ACEs, they don’t usually screen for exposure to pollution or toxins. They don’t usually find out if you suffered from any nutrient deficiencies growing up, of if you had adequate, preventative dental and medical care. What if kids with ACEs are more likely to encounter these additional risk factors?

If we want the strongest proof that toxic stress is to blame for mortality and poor health outcomes, we need experimental evidence. And we have some — from the world of nonhuman animals.

Experimental evidence that social stressors have a negative impact on health

In a carefully controlled experiment on adult male mice, researchers randomly assigned some individuals to experience daily encounters with aggressive, domineering mice. Other individuals were assigned to hang out with more laid-back companions.

The two groups were treated the same in every other respect. Same type of environment. Same food, same housing conditions. But the mice in the more “bullied” group ended up with shorter lifespans — about 12% shorter, on average. They also showed early signs of artherosclerosis, a narrowing of the arteries caused by the build-up of fats and cholesterol (Razzoli et al 2018).

Similar patterns have been documented for nonhuman primates.  For example, monkeys have been raised in captivity, and housed in small social groups. Group members experience the same basic environmental conditions, and receive the same diet and medical care. But some individuals — those who are hierarchically subordinate, and subjected to more social stress — are more likely to develop visceral obesity and coronary artery atherosclerosis (Shively et al 2009).

Moreover, in one experiment, researchers artificially tweaked the dominance hierarchies, controlling who became dominant and who became subordinate. Monkeys assigned to subordinate roles experienced stress-related changes to their immune systems — changes that put them at higher risk for developing diseases of inflammation (Snyder-Mackler et al 2016).

What do such experiments tell us about the health effects of early life adversity? The studies targeted adult animals, not juveniles, so we can’t be sure. But they have shown us that social stressors are enough — by themselves — to cause serious health problems.

And other experiments suggest that baby rodents are sensitive to at least one specific type of early life stressor: being left unattended by a caregiver for several hours at a time. When infant mice are separated from their mothers for periods of 3-4 hours each day, they tend to experience changes in the function and structure of the brain — changes that can increase an individual’s risk for developing pathological behavior patterns (Babicola et al 2021).

Does this mean we’re doomed?

Childhood adversity is very common around the world. In a recent study of more than 200,000 adults living in the United States, 57% had at least one ACE, and nearly 22% had three or more ACEs (Giano et al 2020). There is no doubt that adverse childhood experiences are costing individuals — and society — a great deal.

But we’re far from doomed. We have the power to prevent many ACEs, and we have power to help children cope with — and overcome — the effects of toxic stress.

At the societal level, we can help prevent ACEs with policies and programs that

  • provide families with the support they need to have secure, stable housing and basic needs met;
  • offer parents with affordable, reliable childcare help, and flexible and consistent work schedules;
  • discourage corporal punishment, and attitudes that contribute to domestic violence; and
  • deliver evidence-based therapies, like trauma-focused cognitive behavioral therapy, to kids who have experienced trauma or toxic stress.

We can also help kids in our homes, schools, and neighborhoods by taking a warm and positive approach to children’s needs. Positive parenting strategies and emotion coaching can teach kids to cope with conflict and stress. Secure attachment relationships — and sensitive, responsive parenting — can go a long way toward buffering kids from the effects of toxic stress. Even warm, positive student-teacher relationships can make a difference. To learn more, see my articles,

For evidence-based tips on how we can help kids deal with stress and conflict,  check out these Parenting Science articles:

And don’t forget to care for yourself. When parents are stressed out, kids are more likely to experience stress-related difficulties themselves. Learn more in my articles


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Content last modified 2/2022

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