Adverse Childhood Experiences (ACE)
Definition
Adverse Childhood Experiences (ACE) are among the most significant risk factors affecting individuals’ lifelong health and well-being. This concept first entered the literature in 1998 through a comprehensive study conducted by Felitti and colleagues. Originally initiated within an obesity program, the study analyzed data from more than 17,000 individuals, including their childhood experiences, medical histories, and health examinations, and demonstrated a strong association between early-life trauma and obesity as well as other health problems. With over 25,000 citations to date, this study remains one of the most influential works highlighting the determining role of childhood in shaping an individual’s entire life.
The ACE questionnaire measures ten of the most common adverse experiences in childhood: physical, emotional, and sexual abuse (1,2,3); physical and emotional neglect (4,5); parental divorce (6); parental mental illness (7); parental substance abuse (8); incarceration of a parent (9); and domestic violence (10). Findings show that ACEs are surprisingly common. Sixty-three percent of participants reported experiencing at least one ACE, and those who experienced one were found to have a high likelihood of experiencing others as well. High ACE scores are associated not only with obesity but also with cardiovascular diseases, chronic conditions, depression, addiction, academic failure, and low economic stability. Moreover, ACEs affect not only the individual but also negatively influence children’s development through intergenerational transmission. As Prof. Dr. Medaim Yanık succinctly put it: “childhood trauma corrupts generations.”
But How?
Through which mechanisms do these effects emerge? Research shows that ACEs fundamentally disrupt the body’s stress regulation system. In particular, chronic stress continuously activates the hypothalamic-pituitary-adrenal (HPA) axis, leading to hormonal imbalance. While the HPA axis normally plays a protective role in short-term stress, prolonged and repeated adversities in childhood force this system into a state of “overwork.” As a result, stress hormones such as cortisol are released irregularly; sometimes remaining chronically elevated, and at other times failing to be released sufficiently when needed.
This hormonal imbalance affects not only psychological states but also the entire body. By causing chronic inflammation in the immune system, it makes the body more vulnerable to infections, autoimmune diseases, and long-term chronic conditions. In addition, ACEs lead to structural and functional changes in the brain. Research indicates that volume reduction and functional impairments can occur particularly in the amygdala, which is responsible for emotion regulation, and the hippocampus, which plays a critical role in learning and memory processes. The involvement of the prefrontal cortex leads to weakening in executive functions such as attention, planning, and impulse control.
When all these biological changes come together, individuals’ emotion regulation capacities weaken, their tendency toward risky behaviors increases, and they become more vulnerable to stress. In other words, adverse experiences in childhood do not remain in the past; they leave lasting traces that continue to manifest in adulthood through bodily and neuropsychological processes.
Over time, the concept of ACE has been expanded beyond family-related experiences to include environmental factors such as economic hardship, societal violence, discrimination, and bullying. The ACE-International Questionnaire (ACE-IQ), developed by the World Health Organization, is used to assess this broader framework.
1 + 1 ≠ 2
1 Trauma + 1 Trauma ≠ 2 Trauma
Different models are used to understand the effects of ACEs. The cumulative model assumes that each ACE has equal weight and treats the total score as a risk indicator. However, this approach has limitations because not all ACEs have the same impact. Multiplicative models show that certain combinations of ACEs can create “synergy,” resulting in higher risk than expected. For example, experiencing sexual abuse and poverty together in childhood increases the risk of complex psychopathology in adulthood more than the sum of these factors considered separately. Domain-specific models aim to explain in greater detail how particular types of ACEs relate to specific health outcomes.
Findings on synergy are particularly noteworthy. In women, sexual abuse becomes one of the strongest risk factors when combined with other ACEs, whereas in men, ACE combinations related to poverty are more prominent. Studies on children and adolescents also show that sexual abuse creates the strongest synergies when combined with other ACEs. These results indicate that the effects of ACEs can vary by gender and age, and therefore interventions should be adapted accordingly.
At the same time, there are protective factors that can mitigate the negative effects of ACEs. Strong social support networks, education and economic stability, safe living environments, and access to resources support healthy development despite adverse experiences. Psychological resilience—the capacity to adapt despite trauma—is one of the most critical abilities that can buffer the impact of ACEs.
Conclusion
All these findings demonstrate how important it is to integrate ACE research into clinical practice and social policy. In conclusion, ACE research provides a powerful framework for understanding the effects of childhood trauma on health, psychological well-being, and social functioning in adulthood. However, rather than relying solely on simple cumulative scores, more nuanced approaches that take into account differences between trauma types, their interactions, and individual context should be developed. Addressing risk and protective factors in children’s development in a holistic manner will yield far more effective outcomes in both prevention and intervention.
At this point, there is a resource I would strongly recommend, especially for parents—particularly for Turkish readers: Çocuk Yetiştirirken Travmatik Yanlışlar, Geliştiren Doğrular (Medaim Yanık, Erdem Publications). Written by a psychiatrist who has worked on childhood trauma for many years, this book explains in a clear and guiding manner how our knowledge of trauma can be reflected in everyday parenting, and sheds light on many points that could not be addressed in this text.
We now know how impactful trauma is on individuals’ lives; from this point on, the main task of academia should be to investigate why and how the actors responsible for these traumatic experiences—that is, the conditions and relationships that produce trauma—come into existence and are continuously reproduced.
Reference List
Briggs, E. C., Amaya-Jackson, L., Putnam, K. T., & Putnam, F. W. (2021). All adverse childhood experiences are not equal: The contribution of synergy to adverse childhood experience scores. American Psychologist, 76(2), 243–252. https://doi.org/10.1037/amp0000768
Geffner, R., White, J. W., Hamberger, L. K., Rosenbaum, A., Vaughan-Eden, V., & Vieth, V. I. (Eds.). (2021). Handbook of interpersonal violence and abuse across the lifespan: A project of the National Partnership to End Interpersonal Violence Across the Lifespan (NPEIV). Springer Cham. https://doi.org/10.1007/978-3-319-62122-7
Written By: Clinical Psychologist Ahmet Faruk ERGÜN