INTRODUCTION
Researchers and clinicians have been interested in patients with Post-Traumatic Stress Disorder (PTSD) for many years. The core features of PTSD consist of a stressor that typically defines the etiology of PTSD and the symptoms that define the individual characteristics of PTSD. Nearly one adult in 12 has experienced PTSD at some time in their life. Previous studies have focused on the traumas related to developing combat-related PTSD, particularly during the Vietnam War. Today with the wars in Iraq and Afghanistan, a new generation of veterans is returning. These veterans may be at risk for developing acute and chronic mental health problems related to their war zone experiences.

A corpus of research has shown compellingly the frequency and intensity of exposure to combat experiences is strongly associated with the risk of developing PTSD and related impairment. Recently, however, research efforts have focused on the relationship between childhood trauma and combat-related PTSD. This article looks at this relationship.

OVERVIEW
Adults who report experiences of childhood trauma, abuse and neglect have been found to have higher rates of psychopathology than adults without this experience. The conclusion has been that severe traumas in childhood may have a significant and longstanding effect into adulthood. Those adults with a history of childhood trauma may be vulnerable to developing PTSD, including combat-related PTSD. Individuals abused in childhood may have acquired characteristic methods of coping with stressful experiences, in particular defense mechanisms, which may make them more susceptible to subsequent trauma such as combat stress. Thus, exposure to trauma early in life may increase the vulnerability to psychopathology in response to subsequent stressors such as combat.

The impact of childhood experiences before military service on the development and possible severity of combat-related PTSD has been a research focus since World War I. Although assessments of soldiers prior to deployment in a war zone were used in early screenings of soldiers, these factors proved not to be useful in identifying individuals at risk for developing PTSD. Premilitary experiences continued to be investigated as possible risk factors until the time of the Vietnam War, but these studies were limited in nature.

RELATIONSHIP BETWEEN COMBAT-RELATED PTSD AND CHILDHOOD TRAUMA
Since the Vietnam War, there has been a continued interest in premilitary experiences and risk factors for combat-related PTSD. A connection has been proposed between age and years of education at the beginning of military service and the eventual development of combat-related PTSD. However, environment, childhood family life and social support before joining the military have not been associated with combat-related PTSD. Premilitary antisocial behavior as a risk factor has reported contradictory results. Overall, past studies found experiences and premilitary factors have not been significant predictors of combat-related PTSD. This resulted in an emphasis on the importance of war-related traumatic stressors.

Recent studies have suggested an important relationship between childhood experiences and adult psychopathology, in particular combat-related PTSD. They have examined a number of potential childhood experiences and risk factors but have been limited in their conclusions about the relationship between combat-related PTSD and childhood abuse or childhood trauma in general.

One of these studies compared rates of childhood abuse in Vietnam veterans with and without combat-related PTSD. This study found veterans seeking treatment for combat-related PTSD had higher rates of childhood physical abuse than combat veterans without PTSD. In fact, veterans with PTSD had a higher rate of total childhood traumatic events as a measure of the total score on the Checklist of Stressful and Traumatic Events than veterans without PTSD. Other studies based on military samples have also shown a lack of education and childhood adversity were risk factors.

CONCLUSION
Childhood abuse and neglect can have an impact on an adult’s mental health and particularly combat-related PTSD. The effects of dire childhood experiences on late psychological outcomes are not simple and direct. The manner in which early experiences affect later mental health varies in light of events that occur across the lifespan. With the current high incidence of sexual abuse, physical abuse, violence in our society and combat, the need to understand these complex issues is imperative. The study of traumatized children and the long-term effects of trauma provides an important conceptual starting point from which to study the developmental nature of all psychiatric illness, including combat-related PTSD. The goal is to develop new and effective therapeutic and preventive interventions for psychiatric illness and in particular PTSD. Future studies on the relationship between combat-related PTSD and childhood trauma are needed, since these clinical phenomena should not be considered exclusively in a paradigm of linear causality. It appears a transactional model in which many factors are influential is valid. Studies of risk factors, neurobiological vulnerability, coping behaviors and resiliency could enhance our understanding.

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Dr. Regan is chief of the Tennessee Valley Healthcare System’s Mental Health Care Line and associate clinical professor of Psychiatry, Vanderbilt University School of Medicine; Ms. Barrett is with TVHS Mental Health Care Line; Dr. Gordon is chief of the Psychology Section, TVHS Mental Health Care Line, Nashville.