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Posttraumatic stress disorder (PTSD) is prevalent in military veterans and is associated with reduced mental and physical health functioning as well as overall quality of life (e.g., Hoge, Auchterlonie, & Milliken, 2006; Hoge et al., 2007; Pietrzak et al., 2013). According to the Fifth Edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM-5, American Psychiatric Association, 2013), PTSD consists of 20 different symptoms. However, not all symptoms are required for a diagnosis of PTSD, and PTSD symptom profiles can vary considerably. Indeed, one study found that there are over 600,000 symptom combinations that could yield a DSM-5 diagnosis of PTSD (Galatzer-Levy & Bryant, 2013). Given such heterogeneity, increased attention has been given to the nature and severity of trauma exposures, as well as the role of index traumas in shaping the phenotypic expression of PTSD symptoms. 

A diagnosis of PTSD requires that an individual be exposed to a traumatic event (Criterion A), which is defined as exposure to actual or threatened death, serious injury, or sexual violence by directly experiencing the event; witnessing the event as it occurred to someone else; learning that the event occurred to a close family member or close friend; or experiencing repeated or extreme exposure to aversive details of the traumatic event (American Psychiatric Association, 2013). Although this definition is seemingly specific and clear cut, there is considerable variability in the types of traumas to which an individual may be exposed. Furthermore, the severity and nature of PTSD symptom presentation can vary depending on the type of trauma experienced (Chapman et al., 2013). For example, Litz and colleagues (2018) examined the relation between different categories of traumas and PTSD symptom profiles in treatment-seeking veterans with PTSD; they found that veterans who experienced traumatic loss (i.e., witnessing or learning about the death of a family member, friend, or unit member) had greater severity of re-experiencing (d = 0.39) and avoidance symptoms (d = 0.22) relative to those who endorsed life-threat (i.e., personal exposure to the threat of death or actual or threatened serious injury).  

In the current study, we examined the relation between various index traumas, and the severity and phenotypic expression of PTSD symptoms in a large, nationally representative sample of U.S. veterans. To examine the phenotypic expression of PTSD symptoms, we used a newly proposed phenotypic model of PTSD composed of eight symptom clusters: internally generated intrusions (e.g., distressing traumatic memories), externally generated intrusions (e.g., emotional reactivity to trauma cues), avoidance, negative affect, anhedonia, externalizing behaviors, and anxious and dysphoric arousal (Bar-Haim et al., 2021; Duek et al., 2022).  

The sample consisted of 4,069 veterans who participated in 2019-2020 National Health and Resilience in Veterans Study (NHRVS), a web-based survey of U.S. military veterans conducted from November 2019 to March 2020. Veterans completed the Life Events Checklist for DSM-5 (LEC-5; Weathers et al., 2013), a 17-item self-report measure that assesses exposure to a broad range of traumas, as well as the PTSD Checklist for the DSM-5 (Weathers et al., 2013), which assessed the severity of PTSD symptoms.  

A total of 3,853 veterans reported exposure to one or more traumas on the LEC-5. Index traumas were classified into the following four categories: combat/captivity; interpersonal violence (physical assault, assault with a weapon, sexual assault, or other unwanted sexual activity); disaster/accident (natural disaster, fire or explosion, transportation accident, other serious accident, or exposure to toxic substances); or illness/injury (life-threatening illness or injury, severe human suffering, sudden violent death, or sudden accidental death).  

After adjusting for sociodemographic characteristics and cumulative trauma exposure, results revealed that veterans who reported interpersonal violence and combat/captivity as their index trauma had greater severity of PTSD symptoms relative to veterans who reported illness/injury as their worst event (d = 0.41 for interpersonal violence; d = 0.39 for combat/captivity). Further, veterans who reported interpersonal violence and combat/captivity also had greater severity of PTSD symptoms relative to veterans who reported disaster/accident as their index trauma (d = 0.63 for interpersonal violence; d = 0.57 for combat/captivity).  

With respect to PTSD symptom clusters, after controlling for sociodemographic characteristics and cumulative trauma exposure, results indicated significant differences between the four categories of index traumas on measures of the eight symptom clusters (Figure 1). Specifically, all four index trauma groups differed with respect to internally generated intrusions and negative affect symptoms, with the combat/captivity group reporting the greatest severity of internally generated intrusions and the interpersonal violence group reporting the greatest severity of negative affect symptoms. For externally generated intrusions, avoidance, anhedonia, and dysphoric arousal, significant differences also were observed between the four index trauma groups except for the combat/captivity and interpersonal violence groups. These two groups reported the greatest severity of externally generated intrusions, avoidance, anhedonia, and dysphoric arousal symptoms. For externalizing behaviors, significant differences were observed between the four index trauma groups, with the interpersonal violence group reporting the highest severity of externalizing behaviors. Finally, for anxious arousal, significant differences were observed between disaster/accident and interpersonal violence and combat/captivity groups, as well as between interpersonal violence and illness/injury groups, with the combat/captivity and interpersonal violence groups reporting the highest severity of anxious arousal symptoms. Notably, most of these differences were driven by greater severity of PTSD symptoms in the interpersonal violence and combat/captivity groups relative to the illness/injury and disaster/accident groups.  

Taken together, results of this nationally representative study of U.S. veterans suggest that the severity and phenotypic expression of PTSD symptoms differ with respect to the type of precipitating index trauma. Such findings may help inform the personalization of assessment, monitoring, and treatment of individuals with PTSD that takes into consideration the nature of the index trauma as well as the unique constellation of presenting PTSD symptoms. Further research is needed to examine how index traumas are linked to the broader clinical profile of trauma-related psychopathology and functioning (e.g., substance use, suicidality, quality of life); identify biopsychosocial mechanisms underlying the differential phenotypic expression of PTSD symptoms; and evaluate the efficacy of index trauma and phenotypically tailored intervention approaches for PTSD in veterans and other trauma-affected populations. 

About the Authors 

Dr. Lorig K. Kachadourian completed a B.A in psychology and a Ph.D. in clinical psychology at the University at Buffalo, the State University of New York. She is currently a staff psychologist in both the Outpatient Addiction Recovery Service and the PTSD Outpatient Clinic at the VA Connecticut Healthcare System and an assistant professor of psychiatry at Yale University School of Medicine. Her research interests include anger and aggression and associated risk factors including trauma exposure, posttraumatic stress disorder (PTSD), and substance use. She also is interested in developing and testing alternative treatments for anger and aggression, including mindfulness-based interventions. 

Dr. Or Duek is a clinical psychologist and an assistant professor at the Ben-Gurion University of the Negev. Until recently, he was an associate research scientist at Yale University School of Medicine. His research focuses on the symptomatology and mechanisms of change in PTSD.  

Dr. Ilan Harpaz-Rotem is a professor of psychiatry and of psychology and a member of the Wu Tsai Institute at Yale University. His research focuses on the translational clinical neuroscience, psychophysiology, and neurobiology of PTSD. 

Dr. Robert H. Pietrzak completed a B.A. in psychology at Clark University, M.P.H. in epidemiology, and Ph.D. in clinical psychology with specialization in clinical neuropsychology at the University of Connecticut. He is director of the Translational Psychiatric Epidemiology Laboratory in the Clinical Neurosciences Division of the U.S. Department of Veterans Affairs National Center for PTSD, professor of psychiatry at Yale School of Medicine, and professor of public health (social and behavioral sciences) at Yale School of Public Health. His primary research interests include the psychosocial and genetic epidemiology of traumatic stress and resilience; dimensional models of stress-related psychopathology; and neurobiology of trauma-related disorders. 


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