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All Adverse Childhood Experiences Are Not Equal: The Contribution of
Synergy to Adverse Childhood Experience Scores
Ernestine C. Briggs
1
, Lisa Amaya-Jackson
1
, Karen T. Putnam
2
, and Frank W. Putnam
2
1
UCLA/Duke University National Center for Child Traumatic Stress, Department of Psychiatry and Behavioral Sciences, Duke
University School of Medicine
2
Department of Psychiatry, University of North Carolina at Chapel Hill
The operationalization of childhood trauma and adversity into checklists commonly known as
adverse childhood experiences, or ACEs, has become the most widely adopted methodology
linking traumatic childhoods to adult outcomes. As the number of self-reported ACEs
increase from 0 to 4 or more (4⫹), most studies find a roughly stepwise progression in risk
for a wide range of negative medical and mental health outcomes. A score of 4⫹ACEs, has
become a de facto cutpoint, increasingly used clinically to define “high risk” status for a
myriad of outcomes. Comparisons across studies using a 4⫹cutpoint, however, find con-
siderable heterogeneity in the degree of risk for the same outcomes. In addition to sample and
methodological differences, certain pairs of ACEs comprising the cumulative ACE score
interact synergistically to significantly increase the overall risk beyond the sum (or product)
of the contributions of each ACE to the outcome. This article reviews the empirical literature
on synergistic ACEs including results from a general population adult and a mixed trauma,
youth sample both sufficiently powered to examine over 20 different ACE pairings for
possible synergy. Synergistic pairs of ACEs vary by gender and age group. About 30 – 40%
of the variance in outcomes is accounted for by additive synergistic interactions between certain
pairs of ACEs. Across studies, sexual abuse is the most synergistically reactive ACE. The article
concludes with a discussion of the implications of synergistic ACE pairings for psychologists and
other allied professionals across clinical practice, prevention, research, and policy.
Public Significance Statement
This study reviews evidence that an empiric interaction (synergy) between pairs of adverse childhood
experiences (ACEs) makes larger than expected contributions to outcomes. Sexual abuse, physical
abuse, and neglect are the most synergistic ACEs. The clinical, research, and public policy impli-
cations of synergy are discussed.
Keywords: trauma, adverse childhood experiences, ACEs, synergy, children and adolescents
Vincent Felitti, Robert Anda, and colleagues coined the
term “ACE,” an acronym for adverse childhood experi-
ences, in their seminal article (Felitti et al., 1998). The
original 10 ACEs on their questionnaire involved poten-
Editor’s note. This article is part of a special issue, “Adverse Child-
hood Experiences: Translating Research to Action,” published in the
February–March 2021 issue of American Psychologist. Sharon G. Port-
wood, Michael J. Lawler, and Michael C. Roberts served as editors of the
special issue.
Ernestine C. Briggs Xhttps://orcid.org/0000-0003-4446-4715
Lisa Amaya-Jackson Xhttps://orcid.org/0000-0003-3060-9020
Karen T. Putnam Xhttps://orcid.org/0000-0002-7817-476X
Frank W. Putnam Xhttps://orcid.org/0000-0003-3594-2113
Authors’ Note. This project was developed in part under Grant
2U79SM054284 from the Center for Mental Health Services (CMHS),
Substance Abuse and Mental Health Services Administration (SAM-
HSA), U.S. Department of Health and Human Services (HHS). The
views, policies, and opinions expressed are those of the authors and do
not necessarily reflect those of the funding sources listed above. We
would also like to thank Courtney Smith and Jessica Choi for assisting
with manuscript preparation.
Correspondence concerning this article should be addressed to Ernestine
C. Briggs, UCLA/Duke University National Center for Child Traumatic
Stress, Department of Psychiatry and Behavioral Sciences, Duke Uni-
versity School of Medicine, 1121 West Chapel Hill Street, Suite 201,
Durham, NC 27710, United States. Email: ernestine.briggs@duke
.edu
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American Psychologist
© 2021 American Psychological Association 2021, Vol. 76, No. 2, 243–252
ISSN: 0003-066X https://doi.org/10.1037/amp0000768
243