Behavioural and physiological responses of therapy horses to mentally traumatized humans

https://doi.org/10.1016/j.applanim.2018.05.019Get rights and content

Highlights

  • Therapy horses do not differentiate between humans with PTSD and those without.

  • Therapy horses display more stress behaviours when they are alone in a round pen.

  • Therapy horses are more attentive to humans who are experienced around horses.

  • Therapy horses are calmer when with humans who are inexperienced around horses.

Abstract

The benefits to humans of equine-assisted therapy (EAT) have been well-researched, however few studies have analyzed the effects on the horse. Understanding how differing mental states of humans affect the behaviour and response of the horse can assist in providing optimal outcomes for both horse and human. Four humans clinically diagnosed and under care of a psychotherapist for Post-Traumatic Stress Disorder (PTSD) were matched physically to four neurotypical control humans and individually subjected to each of 17 therapy horses loose in a round pen. A professional acting coach instructed the control humans in replicating the physical movements of their paired PTSD individual. Both horses and humans were equipped with a heart rate (HR) monitor recording HR every 5secs. Saliva samples were collected from each horse 30 min before and 30 min after each trial to analyze cortisol concentrations. Each trial consisted of 5 min of baseline observation of the horse alone in the round pen after which the human entered the round pen for 2 min, followed by an additional 5 min of the horse alone. Behavioural observations indicative of stress in the horse (gait, head height, ear orientation, body orientation, distance from the human, latency of approach to the human, vocalizations, and chewing) were retrospectively collected from video recordings of each trial and analyzed using a repeated measures GLIMMIX with Tukey’s multiple comparisons for differences between treatments and time periods. Horses moved slower (p < 0.0001), carried their head lower (p < 0.0001), vocalized less (p < 0.0001), and chewed less (p < 0.0001) when any human was present with them in the round pen. Horse HR increased in the presence of the PTSD humans, even after the PTSD human left the pen (p < 0.0001). Since two of the PTSD/control human pairs were experienced with horses and two were not, a post-hoc analysis showed that horses approached quicker (p < 0.016) and stood closer (p < 0.0082) to humans who were experienced with horses. Horse HR was lower when with inexperienced humans (p < 0.0001) whereas inexperienced human HR was higher (p < 0.0001). Horse salivary cortisol did not differ between exposure to PTSD and control humans (p > 0.32). Overall, behavioural and physiological responses of horses to humans are more pronounced based on human experience with horses than whether the human is diagnosed with a mental disorder. This may be a reflection of a directness of movement associated with humans who are experienced with horses that makes the horse more attentive. It appears that horses respond more to physical cues from the human rather than emotional cues. This knowledge is important in tailoring therapy programs and justifying horse responses when interacting with a patient in a therapy setting.

Introduction

Over the past few decades, there has been a growing interest in equine-assisted therapy (EAT) as the benefits of interacting with horses for the treatment of individuals with mental illnesses become apparent (Bachi, 2012; Frewin and Gardiner, 2005). The basic premise of such programs is that the immediate and direct feedback from the horse allows the participant to gain awareness of his/her own behaviour or mental state. This presumes that horses perceive and respond to emotional changes in the human, and requires an understanding of horse behavior on the part of program facilitators to foster a positive learning environment and guide mutually constructive interactions between horse and human (Hausberger et al., 2008). However there is little research that analyzes these interactions from the viewpoint of the horse. More attention needs to be accorded to the benefits the animals receive in these programs (Hatch, 2007) as there is the potential for a therapy animal’s welfare to be negatively affected (Wensley, 2008).

Equine-assisted therapy programs begin by introducing the human patient to the horse he/she will interact with. The appropriate pairing of a horse with a participant is essential in developing suitable learning and discovery opportunities for the individual patient. Some EAT practitioners believe that a successful bond between the human and horse is built upon reciprocated trust and dependability that can help establish a successful therapy program (Frewin and Gardiner, 2005). Many practitioners consider the horse itself as the catalyst for therapeutic changes (Kendall et al., 2014). A widely held belief is that the horse can intuit what emotional support the human patient requires and the human is paired with a horse that can fulfill these needs. Anthropocentric labeling of human-horse interactions, such as “the horse knows what the human wants” or that horses are “willing to please” assumes that horses will act benevolently to achieve mutual goals (McGreevy et al., 2009). This assumption can lead to miscommunication and compromise welfare for both human and equine participants.

Literature abounds with the effects of stress placed on humans working in careers of social work, psychology and psychiatry (reviewed in Lloyd et al., 2002). It is reasonable to assume that animals placed in similar environments could also experience stress, and that a number of variables influence a horse’s response to his human partner. It is known, for example, that both the temperament of the horse and the attitude of the human (Hausberger et al., 2008) play a role in the horse-human relationship. Heart rate increased in horses that were petted by humans who were thinking negative thoughts (Hama et al., 1996) and horses being led through a maze by a handler with a negative attitude were less cooperative (Chamove et al., 2002). Humans that were anticipating the occurrence of a frightening incidence while leading or riding a horse caused an increase in both their own and the horse’s heart rate (Keeling et al., 2009), while humans that were nervous around horses caused a decreased heart rate in the horses themselves (Merkies et al., 2014). What is unclear is whether horses are responding to physical or emotional cues from the rider/handler. Programs utilizing EAT invariably encounter humans with physical and emotional emanations, as the focus of the therapy exercises is to allow the participants to recognize and face their mental limitations or fears. Only a handful of studies evaluating the effect of humans on horses involved in EAT have been published. None of these studies (Johnson et al., 2017; Kaiser et al., 2006; McKinney et al., 2015) found differences in mean behaviour scores in horses ridden by recreational riders or physically- or psychologically-handicapped riders. Fazio et al. (2013) found lower concentrations of circulating stress hormones (β-endorphin, ACTH and cortisol) in horses engaged in riding sessions with disabled riders than with recreational riders whereas Johnson et al. (2017) showed higher levels of cortisol in horses when ridden by veterans suffering from Post-Traumatic Stress Disorder (PTSD) compared to experienced riders.

Post-Traumatic Stress Disorder is described as a complex pathological reaction to trauma wherein traumatic experiences may compromise feelings of safety in the affected person’s own body or environment (Tsur et al., 2018). Trauma occurring during childhood can lead to disrupted neurological development which can have long-term impacts on cognitive function (Mueller and McCullough, 2017). These impacts, coupled with fear, anxiety and lack of trust can impede treatment of PTSD. Equine-assisted therapy is an attractive treatment modality as interactions with horses can provide a feeling a safety and modulate arousal and fear responses in humans. The simple act of grooming a horse can overcome touch avoidance and increase body awareness of the individual suffering from PTSD (Mueller and McCullough, 2017).

The importance of fully understanding the variables that affect the horse-human relationship is essential considering that the most significant factor contributing to the risk of human injury when working around horses is the relationship between the horse and the human (Hawson et al., 2010; Keeling et al., 2009). One study reported over 80% of equestrians experienced an injury due to horse riding (Mayberry et al., 2007), leading Gombeski et al. (2017) to recommend that safety around horses be reviewed with staff in all horse organizations. A survey of businesses offering equine-assisted therapy in Florida revealed that all of them reported challenges with their horse training program, often having to resort to outside professionals (Rankins et al., 2017). Although all organizations that certify equine-assisted therapy practitioners consider the interpretation of horse behaviour critical to program success, there exist no standards for teaching or understanding equine behaviour in these certification programs (Kieson and Abramson 2016).

The purpose of this study was to quantify behavioural and physiological responses of therapy horses exposed to humans who have been clinically diagnosed with a psychological or emotional illness, namely Post-Traumatic Stress Disorder (PTSD), compared to those who have not been diagnosed with psychological ailments. Based on previous research in this lab showing less stress behaviours in horses exposed to humans who were nervous of horses (Merkies et al., 2014), it was hypothesized that horses would display fewer signs of behavioural and physiological stress when exposed to humans with PTSD compared to neurotypical individuals. Understanding the therapy horse’s role is fundamental for furthering research, providing suitable training for facilitators, and ensuring appropriate safety measures for all participants while gaining additional insight into the human-animal bond.

Section snippets

Humans

The procedures in this study were approved by the Research Ethics Board (REB) at the University of Guelph for use of human research subjects (REB#13MY036). Four mentally-traumatized females (47.5 ± 17.3 years, 60.3 ± 2.2 kg, 164.3 ± 8.2 cm) clinically diagnosed with PTSD and under current care of a psychotherapist contacted the principal researcher directly after a local media article regarding the research project was released, volunteering to be part of the study. Four neurotypical “control”

Horse heart rate

Horse HR remained relatively constant throughout the BASELINE period (49 ± 15bpm; F(1,9458) = 1.83; P > 0.17). When the horse was exposed to the human, average horse HR did not differ between treatments (48 ± 16bpm in PTSD vs. 46 ± 14bpm in CON; F(1,3725) = 1.56; P > 0.21) even with gait as a covariate. Over the TEST period, horse HR tended to increase by 1.6bpm when exposed to the PTSD individuals (F(1,1934) = 3.51; P < 0.06) whereas when exposed to the CON individuals, horse HR decreased by

Discussion

This study exposed horses individually to pairs of humans who physically resembled each other and moved in a similar way, however one of those humans suffered from PTSD while the other did not. Physiological and behavioural measures showed some differences in responses of the horses to the two treatment groups, however more salient results came from analyzing horse responses to any human presence and to the presence of humans experienced with horses.

Horses did not differentiate between PTSD and

Conclusions

This foundational study provided a quantitative basis for behavioural responses of therapy horses and found no major differences in typical equine stress behaviours indicated by gait, head height, ear position, and distance from the human between PTSD and neurotypical individuals. Horses were less stressed when any human was present with them, and more attentive toward humans who were more experienced with horses. Horses appear to respond more to physical cues from the human rather than implied

Conflicts of interest

The authors declare that there are no conflicts of interest.

Acknowledgements

This work was supported by the Horses and Humans Research Foundation through their Innovation Grant. The authors thank all the human participants and volunteers and Sunrise Therapeutic Riding and Learning Centre for use of their horses and facilities.

References (35)

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