A great deal of work has been carried out on Post Traumatic Stress Disorder, both in animals and people, such that it is arguably beyond question that individuals of any animal species can be affected by PTSD.

 

Unlike ordinary stress, the effects of which tend to disappear reasonably quickly once the stressor(s) are removed PTSD has a long term impact.

 

We might suppose that, while it would be common for horses to come under stress as a result of management and training, the level of such stress would not generally be considered traumatic. But this supposition is perhaps not as safe as might be thought. For it is not necessarily the level of stress that is critical, but the conditions under which the stress occurs – and the precise nature of the stressor(s).

 

The following paragraphs offer an immediate insight into the reasons for this.

 

“Lack of predictability and controllability are the central issues for the development and maintenance of PTSD. The combination of intrusive and numbing symptoms has been consistently noted over the past century.

 

Though the biological underpinnings of response to trauma are extremely complex, forty years of research on humans and other mammals have demonstrated that trauma (particularly trauma early in the life cycle) has long term effects on the neurochemical response to stress, including the magnitude of the catecholamine response, the duration and extent of the cortisol response, as well as a number of other biological systems, such as the serotonin and endogenous opioid system.” (for an extensive review on the psychobiology of trauma, see van der Kolk, 1994).” (1)

 

Typically horses are allowed little or no control over their environment, whether during rest periods or during exercise.

 

Training may well feature a lack of predictability, depending on methods in use.

 

Additionally many young horses experience severe emotional trauma, often at a very early age, as a result of early forced weaning and physical separation from their dam. Such early trauma has been shown to increase individual’s susceptibility to developing PTSD.

 

“Childhood abuse or trauma has a pronounced effect in brain development. It can lead to subtle structural abnormalities in the frontal lobe, which is closely related to the limbic system — the seat of our emotions. These abnormalities may result in deep-seated personality deficits (for example, an inability to be empathetic, or pathological narcissism) that are not readily diagnosable as psychiatric disorders. This may explain why early exposure to traumatic stress or disruptive changes in environment may result in more fundamental behavioral changes that are more often diagnosed as personality disorders.” (2)

“Forty years of primate research has firmly established that early disruption of the social attachment bond reduces the long term capacity to cope with subsequent social disruptions and to modulate physiological arousal. These studies have demonstrated that trauma early in the life cycle has long term effects on the neurochemical response to stress, including the magnitude of the catecholamine response, the duration and extent of the cortisol response, as well as a number of other biological systems, such as the serotonin and endogenous opioid systems” (3) 

When considering the potential impact of this type of trauma it is also quite clear that the event would typically involve a total absence of both predictability and controllability. It might therefore be suggested that in carrying out such management actions the young horse is predisposed toward the development of psychological ill health.

“In dealing with the vets (Vietnam veterans. Ed) I found the same sort of relationship -- those who were diagnosed with PTSD tended to have traumatic childhoods and those who were free of PTSD did not.” (4)

Much that is done to horses is highly likely to build on this early platform for later behavioral problems. (5)

 

Having established a reasonable prima-facie case both for the existence of PTSD in the horse, and for the hypothesis that management systems predispose young horses to suffer from the disorder let’s move on to looking at the biological changes that accompany psychological symptoms.

 

Victims of childhood abuse or trauma and suffers of PTSD experience physical changes to the part of the brain known as the hippocampus. (6)

 

The hippocampus is involved in learning, memory and the management of stress.

 

“The hippocampus also works closely with the medial prefrontal cortex, an area of the brain that regulates our emotional response to fear and stress. PTSD sufferers often have impairments in one or both of these brain regions. Studies of children have found that these impairments can lead to problems with learning and academic achievement.” (7)

 

Studies have shown that the hippocamous is particularly sensitive to damage through stress. (8)(9)(10)

 

The effects of such damage have been shown to include:

 

 

 

Bibliography

 

1.   Bessel A. van der Kolk, M.D. Onno van der Hart, Ph.D.
      Jennifer Burbridge, M.A. Approaches to the Treatment of PTSD.

      http://www.trauma-pages.com/vanderk.htm

 

2 & 4. Dr Bob Murray. PhD. PTSD and Childhood Trauma. 

    http://www.upliftprogram.com/article_ptsd.html

3. Bessel A. Van Der Kolk and Jose Saporta. The Biological Response to Psychic Trauma: Mechanisms and Treatment of Intrusion and numbing. Harvard Medical School: Anxiety Research (U.K.), Volume 4: Pages 199-212. (Received 23 December 1991)

5. Synowski, R. Post-Traumatic Stress Disorder in Arabian Horses.

 in ARABIAN VISIONS Jul/Aug 1994

  http://www.wiwfarm.com/Post_Traumatic_Stress.htm

 

6. Bremner JD, Narayan M (1998): The effects of stress on memory and the hippocampus throughout the life cycle: Implications for childhood development and aging. Develop Psychopath 10:871-886.

 

7. J. Douglas Bremner, M.D. The Invisible Epidemic: Post-Traumatic Stress Disorder, Memory and the Brain

8. Sapolsky RM (1996). Why stress is bad for your brain. Science 273:749-750.

 

9. Sapolsky RM, Uno H, Rebert CS, Finch CE (1990): Hippocampal damage associated with prolonged glucocorticoid exposure in primates. J Neurosci 10:2897-2902.

 

10. Woolley CS, Gould E, McEwen BS: Exposure to excess glucocorticoids alters dendritic morphology of adult hippocampal pyramidal neurons. Brain Res 1990; 531:225-231.

 

11. Luine V, Villages M, Martinex C, McEwen BS (1994): Repeated stress causes reversible impairments of spatial memory performance. Brain Res 639:167-170.

12. Bodnoff SR, Humphreys AG, Lehman JC, Diamond DM, Rose GM, Meaney MJ (1995): Enduring effects of chronic corticosterone treatment on spatial learning, synaptic plasticity, and hippocampal neuropathology in young and mid-aged rats. J Neurosci 15:61-69.

 

13. 14.15. Bremner JD, Southwick SM, Charney DS (1999): The neurobiology of posttraumatic stress disorder: An integration of animal and human research. In: Saigh, P., Bremner, J.D. (Eds.): Posttraumatic Stress Disorder: A Comprehensive Text, Allyn & Bacon, New York, pp. 103-143. In: J. Douglas Bremner, M.D. The Invisible Epidemic: Post-Traumatic Stress Disorder, Memory and the Brain.

 

16. Bremner JD, Krystal JH, Charney DS, Southwick SM (1996): Neural mechanisms in dissociative amnesia for childhood abuse: Relevance to the current controversy surrounding the "False Memory Syndrome". Am J Psychiatry 153(7):FS71-82.