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Research Summaries

Edited by Stephen E. Brock

Genetic and Environmental Influences on Trauma Exposure and PTSD Symptoms: A Twin Study

Summarized by Chris Torem, Rhode Island College (Providence), and Sargent Rehabilitation Center (Warwick), RI.

In 2002, Stein, Jang, Taylor, Vernon, and Livesle published one of the rare twin studies of traumatic stress. A questionnaire and color-photo examination delineated 222 monozygotic from 184 dizygotic twins. The zygosity and sex of twin pairs were reported in five separate groups. The subjects’ mean age fell between 31.30 and 35.99 years old, with the five ranges beginning with 16 years old, and ending with 66, 67, 79, 82, or 86 years old. All were administered the Traumatic Events Inventory, the DSM-IV PTSD Symptoms Inventory, and a lifetime exposure questionnaire. “Lifetime exposure” was divided among three age groups: birth to 6 years old, 7 to 16, and 17 years to the age at the time of the study.

75.4% (n = 612) of participants endorsed at least one traumatic event. They additionally responded to contingency questions rating both the most disturbing event and most disturbing time period following the event. The subjects rated 17 questions, which corresponded to the PTSD symptom-clusters (B-D) utilized by the DSM-IV. Each question was rated from zero (not bothered) to three (very much bothered).

Heritability was analyzed two ways. The trauma exposure items were analyzed using a varimax rotated principal component analysis to remove prominent features of trauma exposure, and a multiple regression analysis (Pearson’s r) was completed on twins in which both reported traumatic events. The PTSD symptoms were grouped into four subscales, each correlating with a cluster (reexperiencing, avoidance, numbing, and hyperarousal). Gender was assessed by grouping the twins: (a) female pairs only, (b) same sex female and male pairs, and (c) the total study group.

Since the correlations between mo nozygotic twins were significantly stronger than dizygotic twins in all groups for assaultive trauma (robbery, sexual assault), the authors concluded that genetic influences account for a significant portion of the variance of this variable. This difference was not found for nonassaultive trauma (natural disaster, death of a family member); hence, genetic influences were not believed to be present. PTSD cluster symptoms were somewhat heritable and high correlations were found between the genetic effects and the PTSD symptoms after exposure to assaultive trauma.

The researchers concluded that the genetic impact on the susceptibility of developing PTSD symptoms was the same as its impact on the exposure to assaultive trauma. They added that genetic links may manifest in pretrauma personality traits, which can have an effect on environmental choices.


Stein, M. B., Jang, K. L., Taylor, S., Vernon, P. A, & Livesle, W. J. (2002). Genetic and environmental influences on trauma exposure and traumatic stress disorder symptoms: A twin study. America Journal of Psychiatry, 159, 1675–1681.

The Effect of Trauma Exposure on Children

Summarized by Talia Sullivan, predoctoral intern, Dallas Independent School District, and University of Central Arkansas.

On December 26, 2004, a tsunami hit several countries across the Indian Ocean. Subsequently, Bhushan and Kumar (2009) conducted research with the children directly and indirectly affected by this natural disaster. They hypothesized that the indirectly exposed subjects would be affected by exposure to the tsunami. However, they hypothesized that those directly exposed would score higher on measures of posttraumatic stress (PTS) and emotional distress when compared to those indirectly exposed. They further hypothesized sex differences and differences due to family structure on PTS measures.

Of the 231 subjects, 130 were directly exposed to the tsunami and 101 were indirectly exposed, based on self-report of the nature of their exposure. There was no objective measure of tsunami-related experiences from participants. The individually administered Impact of Event Scale (IES) was used to identify children likely to experience posttraumatic stress. The Pediatric Emotional Distress Scale (PEDS) was completed by parents and contained four traumatic-specific items out of the 21 items on the scale (the remaining items were general behavior items). Results of the study indicated that the directly and indirectly exposed groups differed significantly on all parameters of the scales. The directly exposed group scored higher on both scales than the indirectly exposed group. When analyzed for sex differences, the data showed that male and female participants differed on almost all of the dimensions of the IES and PEDS in the directly exposed group. Family type played a significant role in the directly exposed group on the IES total score, with individuals from a nuclear family scoring lower. This indicated the positive effect of the family support system as hypothesized by the authors. Although differences were found between sex and family types, a cause–effect relationship could not be established and these factors could not be assumed to be predictors of PTS. This study found that some indirectly exposed children had IES above the scale’s midpoint. The authors noted that members of this group were exposed to the trauma through media reports and that these media images of the tsunami could have been traumatic. These findings suggest that school psychologists in crisis management situations need to be attentive to the needs of both directly and indirectly exposed children.


Bhushan, B., & Kumar, J. S. (2009). Emotional distress and posttraumatic stress in children: The impact of direct versus indirect exposure. Journal of Loss and Trauma, 14, 35–45.

Trauma Among Survivors of Hurricane Katrina

Summarized by LaTasha Greene, predoctoral intern, Dallas Independent School District, and Argosy University, Chicago, IL.

The Journal of Loss and Trauma published an article that outlines the initial steps of assisting survivors of natural and man-made disasters with a focus on Hurricane Katrina survivors. Arthur Whaley (2009) noted that individuals who have been exposed to a natural disaster, such as Hurricane Katrina, may experience some form of trauma. The steps for engaging individuals who survive disasters in mental health care include (a) appropriate reactions to the survivors’ stories and experiences, (b) identifying and interpreting the emotions of Hurricane Katrina survivors, (c) separating appropriate stress responses from mental illness, and (d) turning traumatic experiences into a positive growth opportunity.

Whaley’s research indicated that the majority of individuals who were displaced by Katrina were African Americans. The engagement and retention of people of color in mental health treatment services is an enduring and complex task. Past research suggests that cultural factors were among the barriers to treatment for PTSD. Thus, cultural competence is an additional feature of effective engagement in mental health care for survivors of Katrina and other traumatic events.

Oftentimes, survivors may introduce their need for help through storytelling a narrative of their experiences also known as a “trauma story.” Helping professionals should listen attentively and avoid interrupting the survivor to ask questions. The most effective interventions for traumarelated psychopathology involve using the “trauma story” as the central component of treatment.

Identifying and interpreting emotions of survivors is the next step of the process. Experiencing and witnessing the destructive effects of a hurricane or other disaster can overwhelm a person’s sense of order and beliefs about life. To help survivors receive the appropriate interventions, professionals must distinguish intrusive memories from general memories. Traumatic memories are layered with emotions that include sensory experiences of sights, sounds, or other sensations. Individuals that are more severely traumatized by the disaster may experience emotional numbing or periods of hyperarousal. Once the extent of the survivor’s response to trauma (including consideration of cultural factors) is determined, the appropriate treatment approaches can be identified.

Individuals who experience a natural disaster will display some normal stress responses. Clinicians must accurately separate appropriate stress responses from abnormal emotional reactions to PTSD. Thus, pre-Katrina functioning and mental history should be compared to post- Katrina functioning and mental history to accurately determine an individual’s level of stress and mental state. Additionally, a survivor’s past mental history should be used to determine whether the current mental response is a continuation of an ongoing mental health issue, a relapse that was triggered by recent event, or a new mental problem.

Natural and man-made disasters will lead to trauma and loss of human life and possessions. These losses will create a psychological void in the lives of individuals exposed to the disaster. Some scholars describe Katrina survivors as experiencing a “cultural trauma” or “compound trauma.” Cultural trauma occurs when an event disrupts or destroys a way of life, shatters beliefs, causes a loss of community, produces a constant struggle, and leaves a mark on the collective identity of the survivors. Helping professionals are to assist trauma survivors in rebuilding and creating a new way of thinking; this is known as “posttraumatic growth.” Trauma stories can be used as a medium to pinpoint strengths that can lead to posttraumatic growth.

The present study is described as an outline of steps designed to engage disaster survivors of Hurricane Katrina. Clinicians and other helping professionals may find these steps useful in assisting other individuals who have experience similar natural and man-made disasters.


Whaley, A. L. (2009). Trauma among survivors of Hurricane Katrina: Considerations and recommendations for mental health. Journal of Loss and Trauma, 14, 459–476.

Stephen E. Brock, PhD, is a professor and coordinator of the school psychology program at California State University, Sacramento.