Cover Page

The Encyclopedia of Psychological Trauma

Gilbert Reyes

Jon D. Elhai

Julian D. Ford



April Howell Reyes

Adrienne Fricker-Elhai

Judith Gay Ford


Psychological trauma is among the most discussed, debated, and researched topics in the history of psychology and psychiatry. More than most topics in the mental health disciplines, psychological trauma and its emotional effects have captured the attention and interest of the mainstream culture and worked their way into daily conversations, the arts, and the news and entertainment media. Psychological trauma has also become an important component of the forensic and legal disciplines and regularly influences criminal and civil court decisions. The emotional toll of psychological trauma is a particularly distressing aspect of the suffering caused by global terrorism, genocide, and war. Psychological trauma also affects millions of people who have survived mass disasters such as hurricanes, cyclones, tsunamis, tornadoes, floods, industrial explosions, and epidemic illnesses, and perhaps tens of millions more people who suffer “private disasters” due to deaths, devastating injuries, or threats to them and their loved ones’ lives and safety as a result of life-threatening accidents or illnesses, childhood or elder abuse and neglect, or violence in their families or communities.

From its historical beginnings in psychoanalysis to its adoption by the popular culture, and most recently the production of scientific findings illuminating the genetic and neurobiological aspects of the psychological response to traumatic stress, the investigation of psychological trauma has spawned a plethora of related concepts, terminology, and findings that often are poorly understood even by scientists and professionals working with psychological trauma survivors. Many excellent articles and books have been published that capture important aspects of this topic, but no definitive reference work covering the entire field has ever been published. Thus, an encyclopedic reference on psychological trauma and posttraumatic stress disorder (PTSD) is needed and now is available. The need for such a volume is demonstrated by the rapid growth in the past decade of citations in electronic bibliographic databases (e.g., Medline and PsycInfo), research and clinical journals, and books on psychological trauma and PTSD. Every major health-care, social and behavioral science, medical and neuroscience, education, and human and social service discipline and subspecialty now includes psychological trauma and PTSD as key topics for researchers, educators and trainees, and clinical practitioners.

Public interest among ordinary people from all walks of life, as well as in government and politics, and the media, business, and even the entertainment industries, also has increased dramatically in the past decade, particularly in the wake of the September 11, 2001, terrorist attacks, the Iraq War, and Hurricane Katrina in the United States, the earthquake in China, and natural cataclysms, human-made disasters, terrorism, and political violence internationally. This public interest has culminated in the growing frequency of popular commercial media articles or stories referring to psychological trauma and PTSD. Thus, authoritative factual information about psychological trauma is urgently needed to inform media reports, fictional representations, public opinion, political and governmental laws and policies, and the educational system for people across the life span, and in scientific and professional efforts to assist trauma survivors.


This Encyclopedia presents the best available scientific evidence, clinical practice guidelines, and social policies and initiatives from experts on psychological trauma and PTSD in those fields. The Encyclopedia is intended to be a reference for academic researchers, educators, and students, for traumatic stress clinical specialists from a wide range of disciplines (including psychology, psychiatry, social work, nursing, marriage and family therapy, counseling, criminal justice, and human services), as well as for students, scientists, educators, professionals, administrators, consultants, and informed consumers concerned with issues related to psychological trauma and traumatic stress. The Encyclopedia provides entries that describe the most up-to-date evidence about how psychological trauma plays a role in, and can be dealt with, when people are exposed to violence, disaster, war, occupational stress, serious health problems, parenting and child development, and social issues such as racial, cultural, and socioeconomic disparities and conflicts.

The Encyclopedia was conceived and assembled by the senior editors, but at every step along the way there has been invaluable input from a diverse collection of colleagues who bring a remarkable range of expertise to this final product. At the outset, the senior editors sought the counsel of a distinguished group of associate editors who formed the editorial board for this Encyclopedia. The associate editors who compose this board are internationally recognized experts in 10 broad domains of knowledge regarding psychological trauma: Adjustment and Sequelae, Adult Interventions and Services, Assessment and Diagnosis, Biological Processes, Cognitive and Emotional Processes, Cultural and International Aspects, Developmental Aspects and Child Interventions, Psychological Trauma as a Discipline, Risk and Resilience Factors, and Social and Community Aspects.

With the guidance of the associate editors, a comprehensive set of topics was selected using the definitive bibliographic reference source in the field of psychological trauma, the Published International Literature on Traumatic Stress (PILOTS) database that has been created and rigorously updated by Frederick Lerner under the auspices of the U.S. Department of Veterans Affairs’ National Center for PTSD ( The senior and associate editors identified the leading expert(s) on each topic, and over a 2-year period these experts authored the Encyclopedia entries with detailed editorial input on each entry from the senior editors. The authors were charged with providing concise, thorough, scientifically and clinically grounded summaries of their topics, as well as recommended references that readers could peruse for additional background information or more detailed descriptions of scientific findings, historical and cultural developments, clinical practices, or political and policy implications and initiatives. The editors and readers of the Encyclopedia share a debt of gratitude to the score of expert authors for their lucid, informative, and interesting coverage of each topic.


This Encyclopedia is a comprehensive reference source for laypersons, policy makers, and students, as well as researchers, clinicians, educators, administrators, and advocates, who have questions about psychological trauma. The Encyclopedia provides concise, cutting edge expert summaries of the scientific, clinical, and sociopolitical knowledge addressing such questions as:

While detailed concise answers to these and many other related questions about psychological trauma can be found among the entries in this Encyclopedia, we use this set of eight questions as a framework for providing a brief synopsis to highlight the key issues and facts addressed by this Encyclopedia’s entries.

Defining Psychological Trauma

Many definitions have been proposed to characterize psychological trauma (see: Trauma, Definition). A common feature of past and current definitions of psychological trauma is that it represents events that are emotionally shocking or horrifying, which threaten or actually involve death(s) or a violation of bodily integrity (such as sexual violation or torture) or that render the affected person(s) helpless to prevent or stop the resultant psychological and physical harm. Psychological trauma may involve physical traumas such as severe wounds, injury, illness, or invasive or otherwise painful medical procedures, but most psychologically traumatic events involve only the imminent threat of severe physical trauma, or being an observer or witness to physical traumas experienced by other persons. For example, although war combat is likely to be psychologically traumatic for military personnel or civilian victims, most of these people are never actually severely physically harmed themselves; instead the trauma is psychological in nature because they witness the death or suffering of other persons (and sometimes entire communities), or experience the shock of losing family, friends, or other important persons to tragic deaths, or are threatened with death or horrific devastation to themselves that never actually happen. Thus, it is important to understand that psychological trauma indeed involves a psychological component of terrible or horrifying events, something that occurs independently of the actual physical damage or harm. The psychological experience of trauma is related to the objective nature or impact of traumatic events, but also is an independent unique aspect of trauma beyond the merely physical.

Impact and Aftereffects of Psychological Trauma

To understand the impact that psychological trauma can have on affected persons, communities, organizations, societies, and cultures, it is necessary to learn how people are changed psychologically when they are confronted with death or extreme physical and spiritual violation and suffering, or to an imminent threat to themselves or their loved ones of death or bodily violation. Paradoxically, to understand the psychological impact of trauma, it is important to begin with the biological changes that occur when an individual is faced with the psychological shock of trauma. Research with animals as well as humans has begun to describe the incredibly complex physiological and neurological changes in the brain and body that are produced by traumatic stressors. Relatively automatic shifts occur in how the brain and body respond to stress when survival is threatened or severe bodily violation or pain occurs. These changes in the brain and body’s stress reaction system are adaptive in the crisis—that is, they are essential to survive the danger or harm involved in traumatic events. However, these neurobiological changes that occur in response to traumatic stressors may also lead to alterations in the brain’s systems for processing perceptions, cognitions (thoughts, beliefs, plans, decisions), and emotions that can fundamentally alter a person’s psychological outlook, coping, and adjustment. Traumatic stress-related changes in the brain/body’s stress reaction system also can alter the body’s systems for protecting against pathogens that may cause illness (the immune system), for providing oxygen to every area of the body (the cardiopulmonary system), and for motivation and the seeking of chemical agents such as drugs (the reward system).

Posttraumatic Stress Disorder (PTSD)

Most people have heard of the term PTSD and know that it represents a serious problem that can occur when a person experiences psychological trauma. However, most people do not know that PTSD is a controversial concept that historically was viewed with suspicion by scientists and professionals, and only accepted as a scientifically valid phenomenon when it was included as a diagnosis in 1980 in the Third Edition of the American Psychiatric Association’s Diagnostic and Statistical Manual for Mental Disorders. Only a fraction—perhaps 15% to 20%—of persons who experience psychological trauma will develop PTSD, and most people who develop PTSD do not receive any specialized treatment but nevertheless recover fully or partially within 6 months. There is no definite way to determine in advance if a person affected by psychological trauma will develop PTSD, but there are both risk and protective factors that, respectively, predispose toward or against developing PTSD. Both women and men, girls and boys, may develop PTSD, but research consistently shows that females are almost twice as likely as males to develop PTSD following psychological trauma. The reason for this gender difference is not firmly established (although it has been vigorously researched; see: Gender; Women and Trauma). The difference may be due in part to genetic and sex role socialization: females are more likely than males to develop a number of anxiety and depressive disorders. However, gender differences in the risk of exposure to different types of psychological trauma— females more often experience sexual assault and abuse, males more often are subjected to war and physical assault trauma—also may contribute to gender differences in PTSD.

PTSD involves four general types of symptoms that include unwanted memories (or reminders) of past traumatic experiences, attempts to avoid those memories or reminders, a reduction in the ability to feel positive emotions, and an increase in physical tension, sleeplessness, watchfulness for danger, and negative emotions (particularly anger, frustration, and anxiety).

The PTSD symptoms appear to involve changes in the brain and body’s stress and mood regulation systems that have been identified in scientific neuroimaging research and that may have a genetic basis. PTSD often also involves serious problems with other forms of anxiety (such as panic or phobias), depression, anger and impulse management, and stress-related medical illness (or somatic complaints that cannot be medically diagnosed). Some forms of psychological trauma, particularly those that occur in childhood and that tend to be harmful to the child’s psychological development, and to the relationships the child depends on for security, have been described as “betrayal trauma” (such as child abuse or neglect or family violence; see: Betrayal Trauma). Betrayal traumas appear to lead to PTSD more often than do other forms of psychological trauma (in as many as 50% to 75% of affected persons), and may result in complex forms of PTSD (see: Complex Posttraumatic Stress Disorder).

Prevention and Treatment of PTSD

Psychological trauma is very difficult to prevent, requiring large-scale initiatives aimed at increasing public safety, public health, child care, industrial safety, international relations, and peacekeeping as well as decreasing poverty and sociocultural inequities, epidemic illness, family and community violence, child abuse and neglect, transportation fatalities, terrorism, genocide, war, and climate change. However, none of these vital efforts have, or ever could, completely eradicate psychological trauma. Programs that prepare people to undertake hazardous jobs (such as military personnel, law enforcement or firefighters, emergency medical professionals, disaster responders, journalists who work in dangerous circumstances), or that assist them or survivors of traumatic events immediately afterwards (early interventions such as psychological first aid) may reduce psychological trauma’s adverse impact, but have not been conclusively shown to prevent PTSD.

When psychological trauma has initially occurred and stress reactivity problems are temporarily debilitating (which has been designated as acute stress disorder) or persist for 1 month or more (which is the minimum time period required for a diagnosis of PTSD), treatment has been shown to help many affected persons to manage and overcome these symptoms. The treatment approach that has the strongest scientific evidence base for acute stress disorder and for PTSD is cognitive behavior therapy (CBT). There are several different approaches to CBT for adults, and these also have been adapted for children and adolescents. Still other psychotherapy models have been shown to be effective with very young trauma-exposed children and their parents. Medication (pharmacotherapy) has shown evidence of reducing some PTSD symptoms for adults, as well as the potential to help adults, children, and adolescents with some emotional and behavioral problems that are associated with PTSD. With all age groups, psychotherapy models (including psychodynamic, interpersonal, emotion-focused, group, family, and marital/couple approaches to psychotherapy as well as CBT) have shown a greater ability to produce sustained, long-lasting improvement in PTSD than pharmacotherapy. Pharmacotherapy for PTSD may be indicated if critical symptoms or problems (such as depression or suicidality) require immediate reduction, or when psychotherapy does not result in improvement in specific PTSD or related symptoms.

Research on Psychological Trauma and PTSD

Although much has been learned about psychological trauma and PTSD, many questions remain to be answered by research. Whether there are specific genetic combinations or variations and features of the brain’s structure or activity that may not only predispose a person to develop PTSD, but also that may influence which forms of treatment will be most effective in preventing or facilitating recovery from PTSD, are questions that PTSD neuroscience and treatment scientists are actively investigating. Researchers also are studying differences in how psychological trauma and PTSD affect people at all ages across the life span, from infancy to older adulthood. Factors that determine who is at risk and who is protected from developing not only PTSD, but also a wide range of psychiatric, behavioral, educational/ vocational, interpersonal, and physical health problems that are known to often accompany (i.e., to be comorbid with) PTSD, and how those factors lead to different sequences or trajectories (pathways) of posttraumatic problems (as well as positive adaptations such as resilience or recovery) are another vital research area. To better measure and treat (or prevent) PTSD, research is ongoing to identify the specific psychological factors (emotion, cognition, learning, personality, motivation, integration) that are involved in PTSD’s development and maintenance and that could serve as specific targets for PTSD interventions. Also, clinical research is ongoing internationally to develop and test reliable and valid psychological measures (psychometric and psychophysiological) for the assessment of PTSD and associated posttraumatic changes (including the controversial outcome of posttraumatic growth), and to develop and test effectiveness of psychotherapies and medications for the treatment of children and adults with PTSD (including complex forms of PTSD).

Professional Organizations and Training

A number of professional organizations exist nationally and internationally to help professionals, scientists, educators, students, and laypersons who are interested in becoming involved in studying, treating, or teaching about psychological trauma and PTSD, or in getting up-to-date and accurate facts about PTSD research, assessment, or treatment, or in finding a qualified clinical professional for help for themselves or their family due to having experienced psychological trauma or PTSD. These organizations, such as the International Society for Traumatic Stress Studies (, the International Society for the Study of Trauma and Dissociation (, and the National Child Traumatic Stress Network (, provide information via the Internet, annual conventions, publications, specialized trainings, and special interest groups. Along with the large national and international professional organizations representing the mental health, social and behavioral sciences, and social and human services professions (which have designated Sections, Divisions, Task Forces, Work Groups, and Committees to address psychological trauma and PTSD), these professional organizations have developed practice standards, practice guidelines, and ethical principles to guide clinicians, researchers, and educators in studying and treating psychological trauma and PTSD within the accepted standards for human rights, scientific rigor, and professionalism.

Professional organizations also sponsor thorough scholarly investigations into key social and political issues such as racial, cultural, gender, and age-based disparities in services and scientific knowledge, the controversial question of how to determine the truth or validity of memories of psychological trauma and claims (including for legal/forensic purposes) of PTSD, how to prevent the institutionalization of traumatic practices such as torture or terrorism by ethnic or racial factions or entire governments, and the challenge of delivering evidence-based treatments to vast numbers of people who may benefit from psychosocial intervention, but who have limited or no access to those services.

Governmental and Nongovernmental Organizations and Initiatives

Given the tragic fact that psychological trauma is pervasive worldwide, and particularly prevalent in communities and nations affected by poverty and ethnic strife, governments have increasingly directed attention toward programs designed to prevent or reduce the adverse impact of psychological trauma on high-risk communities and groups. Government sponsored laws, regulations, and initiatives address a variety of forms of psychological trauma including disaster, violence, child maltreatment, and terrorism. Many other organizations operating internationally with nongovernmental funding (such as the Red Cross or Red Crescent, United Nations, World Health Organization, or Interagency Standing Committee) provide humanitarian aid to traumatized communities and societies on a large scale and set standards for governments to use in enhancing the safety, health, and economic and educational opportunities that are known to mitigate against the occurrence of psychological trauma and PTSD and to be vital resources for people, communities, and nations that are recovering from the adverse effects of past or ongoing psychological trauma and both individual PTSD and collective forms of posttraumatic distress. Immigrants from war-torn or violence-infested countries and communities, who are seeking to escape and recover from the effects of their and their families’ exposure to psychological trauma, including those who are formally seeking political asylum, face special challenges that often require the resources of nongovernmental humanitarian organizations.

Culture and Psychological Trauma

Unfortunately, psychological trauma occurs in every part of the world and across all cultures. However, the types of traumatic events and the nature of their impact in terms of traumatic stress problems may differ depending on geography, climate, language, nationality, and cultural norms, values, and practices. Life-threatening and personally violating experiences ubiquitously are followed by traumatic stress reactions, but the extent to which people interpret events as dangerous or harmful, and the specific symptoms that result from traumatic stress reactions, may differ substantially based on culture and associated factors such as language and socioeconomic resources. In some cultures, psychological distress tends to be expressed through medical symptoms or communal or spiritual suffering more than as emotional distress. In some cultures and societies, psychological trauma may have more deleterious effects because access to technological knowledge and economic resources is limited, while in others the social bonds that are essential to recovering from psychological trauma and traumatic stress have been weakened by modernity or traditionally have not been highly valued. Approaches to prevention, diagnosis, and treatment of traumatic stress disorders thus may differ profoundly depending upon the culture in which psychological trauma occurs.


There are several excellent sourcebooks for information about psychological trauma and PTSD, including several comprehensive handbooks published in the past 10 years. However, none of these books is organized to enable readers to rapidly access information that is presented in a concise manner about specific topics related to psychological trauma. Therefore, the Encyclopedia of Psychological Trauma is a unique resource for academic university faculty, librarians, and undergraduate and graduate students, administrators, policy makers and advocates, and practicing clinicians not only within the mental health and social/behavioral sciences but also in medicine, nursing, social work, public health, law, sociology, anthropology, history, political science, the biological sciences, and business.


The Encyclopedia of Psychological Trauma is organized alphabetically by topic and the topic labels were chosen based on the most commonly employed terminology among academic and clinical professionals. Some topics are not covered in a distinct entry and are instead covered in the context of a broader topic. In such cases, readers will find only the title for a topic that has no entry of its own, accompanied by an instruction (See: ) suggesting attention to one or more other topics that might prove relevant to the reader’s interests. Also, because every topic relates to several others, each entry is followed by a list of one or more related topics preceded by the words See also. In addition to these see and see also suggestions, this Encyclopedia provides an extensive index of the topics covered across all entries (see: Subject Index) and an index of authors who contributed entries or who were prominently named in one or more entries (see: Author Index). Readers are also encouraged to use the references and recommended readings provided at the end of an entry for the purpose of learning more than what was covered in this Encyclopedia.

The editors of The Encyclopedia of Psychological Trauma invite the feedback and input of readers. Readers who detect errors or who have suggestions for improving the quality of the next edition of The Encyclopedia of Psychological Trauma are invited to write to us at Input from readers will influence our editorial decisions as future editions of this Encyclopedia are produced.


The editors gratefully acknowledge the invaluable assistance provided by the Associate Editors who served as the Editorial Board for this Encyclopedia. We also appreciate the diligent efforts of Ariel Del Gaizo and Elizabeth Hunziker, the Editorial Assistants who handled much of the communication and organizational tasks necessary for managing the flow of documents and messages among editors and authors. It is difficult to adequately express our debt of gratitude to the contributing authors, who brought to this project the wealth of experience and expertise necessary for producing an authoritative reference work on the complex topic of psychological trauma. At John Wiley & Sons, we were fortunate to work with Executive Editor Patricia Rossi, Editor Isabel Pratt, Editorial Assistant Katie DeChants, and Senior Production Editor Kim A. Nir, all of whom proved to be exceptionally talented, professional, and gracious with their assistance. Finally, the editors wish to acknowledge the groundwork for this volume laid by the international community of scientists, scholars, and practitioners who have developed the field of psychological trauma and traumatic stress over the past several decades. We are particularly grateful to organizations such as the International Society for Traumatic Stress Studies, the International Society for the Study of Trauma and Dissociation, the National Center for Posttraumatic Stress Disorder, and the National Child Traumatic Stress Network, whose leadership in the field of psychological trauma and traumatic stress has benefited thousands of scientists and providers and countless persons who are courageously recovering from psychological trauma.



Adjustment and Sequelae

Jean C. Beckham, PhD
Professor of Psychiatry and Behavioral Sciences
Duke University Medical Center

Patrick S. Calhoun, PhD
Assistant Professor of Psychiatry
Duke University Medical Center

Adult Interventions and Services
B. Christopher Frueh, PhD
Director of Clinical Research
The Menninger Clinic

Barbara O. Rothbaum, PhD
Professor of Psychiatry
Emory University School of Medicine

Joseph I. Ruzek, PhD
Acting Director
Dissemination and Training Division
National Center for PTSD

Assessment and Diagnosis
Matt J. Gray, PhD
Associate Professor of Psychology
University of Wyoming

Frank W. Weathers, PhD
Professor of Psychology
Auburn University

Biological Processes
Karestan C. Koenen, PhD
Assistant Professor
Harvard School of Public Health

Ruth A. Lanius, MD, PhD
Associate Professor of Psychiatry
University of Western Ontario

Cognitive and Emotional Processes
Charles C. Benight, PhD
Professor of Psychology
University of Colorado, Colorado Springs

Onno van der Hart, PhD
Honorary Professor of Psychopathology of Chronic Traumatization
Utrecht University

Cultural and International Aspects
Merle Friedman, PhD
Consulting Psychologist
Johannesburg, South Africa

Anthony J. Marsella, PhD
Professor of Psychology, Emeritus
University of Hawaii

Developmental Aspects and Interventions for Children
Marylene Cloitre, PhD
Professor of Child and Adolescent Psychiatry
New York University Child Study Center

Nancy Kassam-Adams, PhD
Associate Director for Behavioral Research
Center for Injury Research & Prevention
Children’s Hospital of Philadelphia

Effects on Communities
Krzysztof Kaniasty, PhD
Professor of Psychology
Indiana University of Pennsylvania

Fran H. Norris, PhD
Research Professor
Dartmouth Medical School

Psychological Trauma as a Discipline
Christine A. Courtois, PhD
Psychologist in Private Practice
Washington, DC

Risk and Resilience Factors
Brett T. Litz, PhD
Boston University School of Medicine
National Center for PTSD—Boston

Alexander C. McFarlane, MD
Head of the University of Adelaide Node of the Center of Military and Veterans Health
Professor of Psychiatry
University of Adelaide


Matthew J. Friedman, MD, PhD
Executive Director
National Center for PTSD

Daniel W. King, PhD
Research Professor of Psychology and Psychiatry
Boston University

Lynda A. King, PhD
Research Professor of Psychology and Psychiatry
Boston University

Paula P. Schnurr, PhD
Deputy Executive Director
National Center for PTSD


Ariel Del Gaizo, MA
Graduate Student in Clinical Psychology
University of South Dakota

Elizabeth Hunziker, BA
Graduate Student in Clinical Psychology
University of South Dakota