Adverse Childhood Experiences: How Childhood Adversity Shapes Addiction and Chronic Disease Risk

In the 1990s, physician Vincent Felitti was running an obesity program at Kaiser Permanente in San Diego when he noticed that many of his patients who dropped out after losing weight had histories of childhood abuse. That observation led to one of the most influential public health studies ever conducted: the Adverse Childhood Experiences (ACE) Study, a collaboration between Kaiser Permanente and the Centers for Disease Control and Prevention. It found that difficult experiences in childhood, such as abuse, neglect, and household dysfunction, were strongly linked to addiction, mental illness, and many of the leading causes of death in adulthood.

Decades of research since have confirmed and expanded those findings, while also showing that positive experiences and supportive relationships can buffer the effects of adversity. This article explains what adverse childhood experiences are, what research shows about their links to addiction and chronic disease, how adversity may affect the body, and what can be done to prevent ACEs and support healing.

What Are Adverse Childhood Experiences?

Adverse childhood experiences are potentially traumatic events that occur before age 18. The original study measured categories of abuse (emotional, physical, and sexual), neglect (emotional and physical, added in later analyses), and household dysfunction, including witnessing violence against a mother, living with someone who misused substances, living with someone with mental illness or who attempted suicide, parental separation or divorce, and having a household member incarcerated. Each category experienced counts as one point toward an ACE score from 0 to 10. Researchers have since expanded definitions to include experiences such as community violence, discrimination, bullying, and poverty, which can also affect health.

The Original ACE Study

The landmark 1998 paper in the American Journal of Preventive Medicine by Vincent Felitti, Robert Anda, and colleagues surveyed 9,508 adults who had completed medical evaluations at Kaiser Permanente. Most were middle-class, insured, and well educated, which surprised many who assumed childhood adversity was rare in such populations. More than half reported at least one category of adverse experience, and one-quarter reported two or more. The researchers found a graded relationship between the number of categories and every adult health risk behavior and disease they studied. Compared with people with no ACEs, those with four or more had 4 to 12 times higher risks of alcoholism, drug abuse, depression, and suicide attempts; 2 to 4 times higher risks of smoking, poor self-rated health, and sexually transmitted disease; and higher rates of severe obesity and physical inactivity. They also had more heart disease, cancer, chronic lung disease, liver disease, and skeletal fractures.

The Strong Link to Addiction

A 2003 analysis in Pediatrics by Shanta Dube and colleagues examined 8,613 ACE Study participants and found that each adverse experience increased the likelihood of early drug use initiation two- to four-fold. People with five or more ACEs were 7 to 10 times more likely to report illicit drug use problems, addiction to illicit drugs, and injection drug use than those with none. The researchers estimated that 56 to 67 percent of these drug problems could be attributed to adverse childhood experiences. The relationship held across birth cohorts dating back to 1900, suggesting it was not explained by changes in drug availability over time. Many researchers view substance use among people with high ACE scores partly as an attempt to cope with the emotional effects of trauma.

Evidence From Around the World

Studies in many countries have replicated the ACE findings. A 2017 systematic review and meta-analysis in The Lancet Public Health by Karen Hughes, Mark Bellis, and colleagues pooled 37 studies with 253,719 participants. People with four or more ACEs had higher risks of every health outcome examined. Associations were weak to modest for physical inactivity, overweight, and diabetes; moderate for smoking, heavy drinking, poor self-rated health, cancer, heart disease, and respiratory disease; strong for sexual risk-taking, mental illness, and problematic alcohol use; and strongest, with odds more than seven times higher, for problematic drug use and interpersonal and self-directed violence. The authors noted that the outcomes most strongly linked to ACEs, such as violence, mental illness, and substance use, are themselves risk factors for ACEs in the next generation.

How Common Are ACEs Today?

A 2019 CDC Vital Signs report in Morbidity and Mortality Weekly Report by Melissa Merrick and colleagues analyzed survey data from 25 states between 2015 and 2017. Nearly one in six adults, 15.6 percent, reported four or more types of adverse childhood experiences. ACEs were significantly associated with poorer health, risky health behaviors, and socioeconomic challenges such as not completing high school and unemployment. The researchers estimated that preventing ACEs could potentially reduce cases of depression by up to 44 percent, chronic obstructive pulmonary disease by 27 percent, and heavy drinking by 24 percent, along with reductions in heart disease, diabetes, and other conditions.

How Childhood Adversity Affects the Body

Why would childhood experiences affect heart disease or cancer decades later? A 2006 review in European Archives of Psychiatry and Clinical Neuroscience by Robert Anda, Vincent Felitti, J. Douglas Bremner, and colleagues described how evidence from neurobiology and epidemiology converges. Chronic, severe stress in childhood, sometimes called toxic stress, can alter the development of brain regions involved in emotion, memory, and decision-making, such as the amygdala, hippocampus, and prefrontal cortex, and can disrupt stress hormone systems. In the ACE Study, ACE scores showed dose-response relationships with 18 outcomes spanning mental health, substance use, sexual behavior, memory, and physical health. These biological changes may increase vulnerability to mental illness and addiction, and chronic activation of stress systems may contribute to inflammation and cardiovascular and metabolic disease. Health behaviors such as smoking, drinking, and overeating, often used to cope with distress, add further risk.

The Power of Positive Childhood Experiences

ACE research can feel deterministic, but newer studies emphasize resilience. A 2019 study in JAMA Pediatrics by Christina Bethell and colleagues, using a representative survey of 6,188 Wisconsin adults, measured seven positive childhood experiences, such as being able to talk with family about feelings, feeling that family stood by them in difficult times, enjoying community traditions, feeling a sense of belonging in high school, feeling supported by friends, having at least two non-parent adults who took genuine interest, and feeling safe and protected by an adult at home. Adults who reported six or seven positive experiences had 72 percent lower odds of depression or poor mental health than those reporting zero to two, and the associations held regardless of how many ACEs they had experienced. They were also more than three times as likely to report always having the social and emotional support they needed.

Preventing ACEs

Implications for Addiction Treatment

The strong link between ACEs and addiction has reshaped how many clinicians approach substance use disorders. Rather than viewing addiction solely as a moral failing or simple pleasure-seeking, trauma-informed approaches recognize that many people with substance use disorders have histories of significant adversity and may be using substances to manage pain, anxiety, or emotional distress. Treatment that addresses trauma alongside substance use, offers safety and choice, and avoids retraumatizing practices may improve engagement and outcomes. Integrated programs that combine medication for opioid or alcohol use disorder with trauma-focused therapy are increasingly common.

Healing From Childhood Adversity

Adults with high ACE scores can and do heal. Evidence-based therapies for trauma include trauma-focused cognitive behavioral therapy, cognitive processing therapy, prolonged exposure therapy, and eye movement desensitization and reprocessing. Supportive relationships, whether with partners, friends, mentors, or community groups, are among the strongest protective factors. Regular physical activity, adequate sleep, mindfulness practices, and avoiding substances used to cope can help regulate stress systems. For children who have experienced adversity, a stable, nurturing relationship with at least one caring adult can substantially buffer the effects. If you are struggling with the effects of childhood trauma, a licensed mental health professional can help, and if you are in crisis, contact local emergency services or a crisis line in your country.

Should Doctors Screen for ACEs?

Some health systems have begun screening patients for ACEs. California launched a statewide initiative in 2020 encouraging and reimbursing ACE screening in primary care for children and adults. Supporters argue that screening helps clinicians understand patients’ risks, provide trauma-informed care, and connect families to support. Critics caution that ACE scores were designed for population research, not individual prediction, and that screening without adequate resources for follow-up could cause distress or stigma. Most experts agree that if screening is used, it should be paired with supportive responses and access to services, and that ACE scores should never be used to label or predict an individual’s future.

What Parents and Caregivers Can Do

Parents and caregivers can reduce ACE risk and build resilience by creating safe, stable, and nurturing relationships; responding warmly to children’s needs; talking openly about feelings; seeking help for their own mental health or substance use problems; and building support networks. Even when adversity occurs, such as divorce or a family member’s illness, children fare better when they have caring adults who help them understand and cope with what is happening. Community resources, including parenting programs, home visiting services, and family support centers, can help parents under stress.

Limitations of ACE Research

ACE research has important limitations. Most studies rely on adults recalling childhood experiences, which can be affected by memory and current mood. The ACE score counts categories equally, though the severity, frequency, timing, and duration of adversity vary greatly. Many studies are cross-sectional and cannot prove that ACEs cause later problems, though the consistent dose-response relationships and biological evidence strengthen the case. The original ACE categories also omitted experiences such as poverty, racism, community violence, and bullying, which newer research includes. Importantly, ACE scores describe population risks and are poor predictors of any individual’s outcomes; many people with high scores live healthy lives.

ACEs Across Generations

ACEs can be passed between generations. Parents who experienced childhood adversity may face higher risks of mental illness, substance use, and relationship difficulties, which can in turn create adverse environments for their own children. This intergenerational cycle is not inevitable. Support for parents, treatment for mental health and substance use problems, and programs that strengthen families can interrupt it. The Hughes meta-analysis emphasized that preventing ACEs and building resilience are essential to improving the health of future generations.

Schools and Communities

Schools can play a major role in buffering the effects of adversity. Trauma-informed schools train staff to recognize signs of trauma, respond with support rather than punishment, and create environments where students feel safe and connected. A sense of belonging at school was one of the positive childhood experiences associated with better adult mental health. Communities can support children and families through safe parks, youth programs, mentoring, accessible mental health services, and economic opportunities. Policies that reduce poverty and housing instability also reduce stress on families.

ACEs and Heart Disease

Among physical health outcomes, the link between ACEs and cardiovascular disease has received particular attention. In the original ACE Study, people with four or more ACEs had higher rates of ischemic heart disease, and later studies have linked childhood adversity to high blood pressure, inflammation, and heart attacks. Part of this link runs through behaviors such as smoking, heavy drinking, and physical inactivity, which are more common among people with high ACE scores. But research suggests that chronic stress itself may contribute by keeping the body’s stress response activated, raising blood pressure and promoting inflammation over many years. Addressing both behaviors and stress is important for heart health in people with childhood adversity.

ACEs and Cancer

The original study and later meta-analyses found moderately higher cancer risks among people with multiple ACEs. Much of this association likely reflects higher rates of smoking, heavy drinking, obesity, and sexually transmitted infections that can cause cancer, such as human papillomavirus. Lower use of preventive health care, including cancer screening, may also contribute. These findings suggest that supporting people with histories of adversity to quit smoking, reduce drinking, and access screening could help reduce cancer burden.

Why Some People Are More Resilient

Not everyone exposed to adversity develops health problems. Researchers have identified factors that promote resilience, including secure attachment to at least one caregiver, supportive relationships outside the family, a sense of competence and control, cultural and spiritual connections, and access to resources such as education and health care. Genetic differences may also influence how people respond to stress. Resilience is not a fixed trait but can be built through relationships and experiences at any age, which is why positive childhood experiences and later supportive environments matter so much.

Understanding Your Own ACE Score

Some people find it helpful to understand their own ACE history, while others find it distressing. ACE questionnaires are widely available, but it is wise to reflect on them with a supportive person or professional, especially if they bring up painful memories. Knowing your history can help explain patterns in health or relationships and motivate healthy changes, but a score is not a diagnosis or a prediction. Many people find that understanding the impact of their experiences is an important step toward healing.

The Economic Cost of ACEs

The health consequences of ACEs carry large economic costs through medical care, lost productivity, criminal justice involvement, and reduced educational attainment. Researchers have estimated that the annual costs of health consequences associated with ACEs in North America and Europe reach into the trillions of dollars. The CDC’s 2019 report found that ACEs were associated with not completing high school and unemployment as well as disease. Because prevention programs such as home visiting and parenting support cost far less than treating the consequences, many economists and public health experts argue that investing in ACE prevention offers substantial returns.

Looking Ahead

Research on ACEs continues to evolve, with growing attention to community-level adversity, racism, and economic hardship, as well as to the biological pathways linking early stress to disease. Programs that promote positive childhood experiences and support families are expanding, and trauma-informed approaches are increasingly common in health care, schools, and social services. The central lesson of ACE research is hopeful: because so much adult disease has roots in childhood, protecting children and supporting families is one of the most effective ways to improve lifelong health.

A Balanced View

Research consistently shows that adverse childhood experiences are common and strongly associated with addiction, mental illness, and chronic disease in adulthood, with the strongest links to problematic drug use and violence. These findings have transformed how health professionals think about the roots of addiction and illness. At the same time, ACE scores describe population risk, not individual destiny, and positive childhood experiences, supportive relationships, and effective treatment can substantially reduce harm. Prevention, early support, and trauma-informed care offer powerful opportunities to improve health across generations.

Practical Takeaways

If you experienced childhood adversity, know that healing is possible and that effective therapies and supportive relationships help. Tell your health care provider if you think childhood experiences affect your health. If you are a parent, focus on safe, stable, nurturing relationships and seek help for your own stress, mental health, or substance use. Support community programs and policies that strengthen families and connect children with caring adults.

Common Myths

“Childhood adversity only happens in poor families.” The original study found ACEs common among middle-class, insured adults.

“A high ACE score means you will be unhealthy.” ACEs raise risk but do not determine outcomes; many people with high scores thrive.

“Addiction is just a lack of willpower.” Research links addiction strongly to childhood trauma and its effects on the brain and stress systems.

“Kids forget early experiences.” Early adversity can affect brain development and health even without conscious memories.

“Nothing can be done once ACEs occur.” Supportive relationships, therapy, and healthy coping can reduce their effects.

Key Terms

Adverse childhood experiences (ACEs): Potentially traumatic events in childhood, including abuse, neglect, and household dysfunction.

ACE score: The number of ACE categories a person experienced.

Toxic stress: Prolonged activation of stress response systems without adequate adult support.

Positive childhood experiences (PCEs): Supportive relationships and experiences that promote resilience.

Trauma-informed care: Care that recognizes the effects of trauma and emphasizes safety, trust, and choice.

The Bottom Line

The Adverse Childhood Experiences Study and the research that followed show that childhood abuse, neglect, and household dysfunction are common and strongly linked to adult addiction, mental illness, and chronic disease. People with five or more ACEs were 7 to 10 times more likely to develop drug addiction, and a meta-analysis of more than 250,000 people found four or more ACEs associated with higher risks of every outcome studied. Nearly one in six U.S. adults reports four or more ACEs, and preventing them could substantially reduce depression, lung disease, and heavy drinking. Yet positive childhood experiences, such as supportive family, friends, and caring adults, were associated with 72 percent lower odds of adult depression regardless of ACE levels. Preventing adversity, building resilience, and providing trauma-informed care offer powerful paths to better health.

Frequently Asked Questions

What are adverse childhood experiences?

Potentially traumatic childhood events such as abuse, neglect, and household problems like substance misuse, mental illness, violence, or incarceration.

How are ACEs linked to addiction?

Each ACE raised the risk of early drug use, and people with five or more ACEs were 7 to 10 times more likely to develop addiction.

Do ACEs affect physical health?

Yes. Multiple ACEs are associated with higher risks of heart disease, cancer, lung disease, and other chronic conditions.

Can the effects of ACEs be reversed?

Supportive relationships, positive experiences, therapy, and healthy coping can substantially reduce their effects.

How can ACEs be prevented?

By supporting families economically and socially, teaching parenting and relationship skills, connecting children with caring adults, and providing early help.

This article discusses childhood trauma. If you are affected, a licensed mental health professional can help. If you or someone you know is in danger or crisis, contact local emergency services or a crisis line in your country.

References

1. Felitti VJ, Anda RF, Nordenberg D, et al. Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. The Adverse Childhood Experiences (ACE) Study. American Journal of Preventive Medicine. 1998;14(4):245–258. PMID 9635069
2. Dube SR, Felitti VJ, Dong M, et al. Childhood abuse, neglect, and household dysfunction and the risk of illicit drug use: the adverse childhood experiences study. Pediatrics. 2003;111(3):564–572. PMID 12612237
3. Hughes K, Bellis MA, Hardcastle KA, et al. The effect of multiple adverse childhood experiences on health: a systematic review and meta-analysis. Lancet Public Health. 2017;2(8):e356–e366. PMID 29253477
4. Merrick MT, Ford DC, Ports KA, et al. Vital Signs: Estimated Proportion of Adult Health Problems Attributable to Adverse Childhood Experiences and Implications for Prevention – 25 States, 2015–2017. MMWR Morbidity and Mortality Weekly Report. 2019;68(44):999–1005. PMID 31697656
5. Anda RF, Felitti VJ, Bremner JD, et al. The enduring effects of abuse and related adverse experiences in childhood. A convergence of evidence from neurobiology and epidemiology. European Archives of Psychiatry and Clinical Neuroscience. 2006;256(3):174–186. PMID 16311898
6. Bethell C, Jones J, Gombojav N, et al. Positive Childhood Experiences and Adult Mental and Relational Health in a Statewide Sample: Associations Across Adverse Childhood Experiences Levels. JAMA Pediatrics. 2019;173(11):e193007. PMID 31498386

Last updated: October 6, 2026