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F. McMillan1
1Best Friends Animal Society, Animal Care, Kanab- UT, USA
Best Friends Animal Society, Kanab, Utah, USA, email:
Psychological trauma in humans has been well- described for several decades. More recently, a
rapidly growing body of research provides extensive evidence supporting the existence of psychological trauma and its characterization in nonhuman animals. Although posttraumatic stress disorder (PTSD) has received the most attention from both the public and researchers, a key aspect of psychological trauma is that posttraumatic psychopathology includes far more than PTSD, in 2 senses. In the first sense, PTSD constitutes the most severe outcome on a continuum of fear-based responses to a potentially traumatic experience (PTE). At the other end of this continuum mild posttraumatic fears can be found, and in between are all levels of severity
of fears as well as additional important psychological changes along with the fears (such as intrusive memories, flashbacks, nightmares, and more). The diagnosis of PTSD is made only if an individual exhibits a certain number of symptoms from each of 4 quite well-defined symptom clusters over a certain period
of time. As specified in the Diagnostic and Statistical Manual of Mental Disorders (DSM 5), in addition to the history of exposure to a traumatic event, the 4 symptom clusters that distinguish PTSD from other posttraumatic psychological disturbances are: (1) reexperiencing
the trauma through intrusive memories, dissociation, flashbacks, and nightmares; (2) avoidance of anything reminiscent of the traumatic event; (3) negative alterations in cognition and mood; and (4) hyperarousal symptoms such as hypervigilance and increased startle response (not present before the trauma). The criteria for children 6 years and younger – which likely have greater applicability to animals – require fewer symptoms in each of the diagnostic clusters.One of the most important lessons obtained from research is that most survivors
of single, discrete traumatic events do not develop any form of psychopathology. People who experience even the most harrowing of traumatic experiences are likely to experience at least short-term distress but do not develop PTSD or any other posttraumatic psychiatric disorder. The most common trajectory is for recovery over time. Only a minority of individuals develop distress
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and functional impairment that rise to meet the criteria for one or more of the psychiatric disorders. Another important development in recent years is the recognition that many people exposed to a PTE show enough of
the symptoms of PTSD to cause distress and functional impairment but too few symptoms to meet the diagnostic criteria for PTSD. In fact, research shows that the number of people in this category after trauma outnumber the people who receive the diagnosis of PTSD. Accordingly, numerous researchers feel that the more appropriate term for this continuum of posttraumatic responses is “posttraumatic stress”, or PTS (see Figure 2). Here, PTSD would be the most severe form of PTS. Forms of PTS that fail to reach the threshold for a diagnosis of PTSD are referred to as “subthreshold PTSD” (also, “partial PTSD”). This conceptualization of PTS takes on even greater importance as we discuss posttraumatic conditions
in animals, where meeting certain PTSD diagnostic criteria is often difficult to confirm (e.g., flashbacks
and nightmares). In this way, we can refer to animals experiencing PTS without the concern of whether they strictly cross the diagnostic threshold for PTSD.
The second sense of the assertion that posttraumatic psychopathology extends well beyond PTSD is that PTSD does not capture the full spectrum of posttraumatic disorders. Posttraumatic disorders other than (or coexist with) PTSD include specific phobia, generalized anxiety disorder, and depression, among others.
Current research has identified the primary physiological system involved in PTS to be the hypothalamic- pituitary-adrenal (HPA) axis, which appears to undergo pronounced and persistent dysregulation. Studies
of PTSD show that fear is the key emotion involved
in the disorder and the adaptive functioning of fear conditioning, with the capability to distinguish between safe and unsafe stimuli and facilitate identification of danger, fails this disorder. Rather than a normal level of alertness with relaxed attention, individuals with PTSD have an elevated baseline of arousal: the individual suffering from PTSD continues to function in a “red alert” status of readiness, behaviorally primed for another stressful event. To severely affected individuals, almost every place becomes perceived as unsafe, resulting in a loss of one’s sense of security.
As mentioned above, a large body of research provides compelling evidence in support of the notion that animals experience psychologica trauma. But do they experience PTSD as it occurs in humans? In the laboratory, a large number of animal models of PTSD have demonstrated phenomenology that closely resembles that of PTSD
in humans. However, the subjective experiences of some symptoms such as flashbacks, nightmares, and intrusive recollections cannot currently be ascertained. Most animal models of PTSD are based on exposure

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