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EDIZIONI FS Publishers
152
Systematic Review in Occupational Health Psychology
Animal-assisted interventions and post-traumatic stress
disorder of military workers and veterans: A systematic
review
Francesco CHIRICO
1
, Ilaria CAPITANELLI
2
, Behdin NOWROUZI-KIA
3
, Aaron
HOWE
4
, Kavita BATRA
5
, Manoj SHARMA
6
, Lukasz SZARPAK
7
, Michal PRUC
8
,,
Gabriella NUCERA
9
, Giuseppe FERRARI
10
, Claudio Giovanni CORTESE
11
, Maria
Michela GIANINO
12
, Daniela ACQUADRO-MARAN
13
Affiliations:
1
Post-Graduate School of Occupational Health, Università Cattolica del Sacro Cuore, Rome, Italy. Health Service
Department, Italian State Police, Ministry of the Interior, Milan, Italy. E-mail: francesco.chirico@unicatt.it.
ORCID:0000-0002-8737-4368
2
Prevention Service in the Workplace (SPRESAL), Local Health Unit Roma 4, Civitavecchia, Italy. E-mail:
ilaria.capitanelli@yahoo.it. ORCID: 0000-0002-9199-1705
3
Department of Occupational Science and Occupational Therapy, University of Toronto, Canada. E-mail:
behdin.nowrouzi.kia@utoronto.ca. ORCID: 0000-0002-5586-428
4
Department of Occupational Science and Occupational Therapy, University of Toronto, Canada University of Toronto,
Canada. E-mail: aa.howe@utoronto.ca. ORCID: 0000-0003-3610-8614
5
Department of Medical Education, Kirk Kerkorian School of Medicine at UNLV, University of Nevada, Las Vegas,
Nevada, United States of America, Email: Kavita.batra@unlv.edu. ORCID: 0000-0002-0722-0191. Office of Research,
Kirk Kerkorian School of Medicine at UNLV, University of Nevada, Las Vegas, United States of America
6
Department of Social and Behavioral Health, School of Public Health, University of Nevada, Las Vegas, Nevada, United
States of America, Email: manoj.sharma@unlv.edu. ORCID: 0000-0002-4624-2414
7
Institute of Outcomes Research, Maria Sklodowska-Curie Medical Academy, Warsaw, Poland. Maria Sklodowska-Curie
Bialystok Oncology Center, Bialystok, Poland. Henry JN Taub Department of Emergency Medicine, Baylor College of
Medicine Houston, Houston, TX, United States. E-mail: lukasz.szarpak@gmail.com. ORCID: 0000-0002-0973-5455
8
Research Unit, Polish Society of Disaster Medicine, Warsaw, Poland E-mail: m.pruc@ptmk.org ORCID: 0000-0002-
2140-9732
9
Department of Emergency, Fatebenefratelli Hospital, ASST Fatebenefratelli and Sacco, Milan, Italy. E-mail:
gabriellanucera@gmail.com. ORCID: 0000-0003-1425-0046
10
SIPISS, Milan, Italy. E-mail:ferrari@sipiss.it. ORCID:
11
Department of Psychology, Università di Torino, Torino, Italy. E-mail: claudio.cortese@unito.it. ORCID: 0000-0003-
2339-9838.
12
Department of Public Health and Paediatrics, Università di Torino, Torino, Italy. E-mail: mariola.gianino@unito.it.
ORCID: 0000-0003-4239-7475.
13
Department of Psychology, Università di Torino, Torino, Italy. E-mail: daniela.acquadro@unito.it ORCID: 0000-0002-
9924-4093.
*Corresponding Author:
Adjunct Professor, Francesco Chirico, Via Umberto Cagni, 21 20162 Milan, Italy. E-mail: francesco.chirico@unicatt.it.
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Abstract
Introduction: Animal-Assisted Interventions (AAIs) have been increasingly used in the workplace to
mitigate the effect of work-related stress and improve psychological well-being among employees.
Military workers returning home from combat and veterans face a high burden of post-traumatic
stress disorders (PTSD). This systematic review aimed to investigate the potential benefits of AAIs
on military workers and veterans affected by PTSD.
Methods: A systematic review was conducted across Scopus, PubMed Central/Medline, Web of
Science, and Google Scholar in December 2021 and June 2022 using predefined search criteria. All
types of studies published in the English language were included except editorials, commentaries,
and narrative reviews. Studied published from January 2001 to December 2021 were included. We
followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020
reporting guidelines for this systematic review. The assessment of study quality was carried out with
a 16-item Quality Assessment Tool for Studies with Diverse Designs (QATSDD)
Results: Overall, 25 studies were finally included in this systematic review. Most of the AAIs were
canine-assisted programs (n=12) and therapeutic horseback riding or equine-assisted psychotherapy
(n=11). There was only one intervention study utilizing a pinnipeds-based program (n=1), while one
study was based on several types of animals (n=1).
Out of 25 studies focusing on the effects of AAIs on PTSD in the military (n=3) and veterans (n=21),
the majority of them (n=18) observed significantly lower PTSD symptomatology following AAIs.
Three studies observed no statistically significant difference in PTSD symptomatology.
Discussion: Our findings indicated that implementing AAI programs among military workers and
veterans may improve their psychological well-being and reduce the severity of PTSD symptoms.
Policymakers and occupational health services should consider adopting AAIs during military
service and after military discharge to support the mental health of military workers.
Take-home message: This systematic review provides evidence to support the implementation of
AAIs as adjunctive therapy to alleviate PTSD symptoms among military workers and veterans.
Keywords: Animal-assisted Interventions; Military veterans; Pets; Occupational health; Workplace.
Cite this paper as: Chirico F, Capitanelli I, Nowrouzi-Kia B, Howe A, Batra K, Sharma M, Szarpak L,
Pruc N, Nucera G, Ferrari G, Cortese CG, Gianino MM, Acquadro-Maran D. Animal-Assisted
Intervention and military veterans’ psychological health: A systematic review of the literature. J
Health Soc Sci. 2022;7(2):152-180. Doi:
10.19204/2022/NMLS4
Received: 15 March 2022; Accepted: 15 June 2022; Published: 15 June 2022
INTRODUCTION
Psychosocial hazards (PHs) in the workplace have been identified as one of the key emerging
risks in occupational safety and health [1
–
7]. PHs are defined as “those aspects of work design and
the organization and management of work, and their social and environmental context, which may
have the potential to cause psychological or physical harm” [8]. Working conditions that may affect
the relationship between workers and their working environments encompass a broad spectrum of
organizational and environmental factors, ranging from working time (e.g. hours of work, rest
periods, and work schedules) to physical and mental (e.g. cognitive and emotional) demands, as well
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as remuneration and other organizational issues [9
–
11]. Moreover, occupational PHs range from
work-related stress (WRS) and emotional demands to workplace violence and critical events or
incidents [1
–
7]. Some consequences of occupational stressors include anxiety, depression, and
burnout syndrome (BOS) [9
–
11]. The European Agency for Safety and Health at Work (EU-OSHA)
has defined WRS as a “tension experienced when the demands of the work environment exceed the
workers’ ability to cope with or control them” [12]. BOS has been recently labeled by the World
Health Organization (WHO) as an occupational phenomenon resulting from chronic workplace
stress that has not been successfully managed, and is characterized by emotional exhaustion,
cynicism, and reduced professional efficacy [13,14].
According to the Diagnostic and Statistical Manual of Mental Disorders - Fifth Edition (DSM-5),
trauma-and-stressor-related disorders, adjustment disorders, and post-traumatic stress disorders
(PTSD) may be diagnosed as a consequence of exposure to occupational stressors [15]. According to
DSM-5 TR, adjustment disorders with mixed disturbances or emotions (anxiety and/or depression)
and conduct, as well as post-traumatic stress disorders may result from occupational stressors of
different severity and nature [16,17]. Adjustment disorders and especially, PTSD have been
associated with critical events and workplace violence, including physical, psychological (bullying,
harassment), and sexual violence experienced in the workplace environment. PTSD and BOS are two
relevant psychological disorders related to high suicidality and turnover intention rates among
healthcare and frontline workers, especially in the context of the current COVID-19 pandemic [18
–
21].
PTSD was first coded in the Diagnostic and Statistical Manual of Mental Disorders (DSM) 3 in 1980,
driven in part by sociopolitical aftereffects of the Vietnam War [22]. It is a complex and evolving
biological, psychological, and social entity, often described by war and disaster survivors as the result
of direct or secondhand exposure to assaults, terror attacks, violence, and accidents. PTSD symptoms
can interfere with interpersonal and occupational function and manifest in psychological, emotional,
physical, behavioral, and cognitive impairment. Military workers are exposed to an array of
potentially and suddenly traumatizing experiences during wartime. Furthermore, they may also
experience non-military-related traumatizing experiences, such as interpersonal violence, and
physical or sexual abuse [18,19,22].
For this reason, in European Union, OSH laws (Framework Directive 89/391/EEC) require public
and private employers of all occupational sectors, including military sectors, to carry out a mandatory
and documented risk assessment process for evaluating the likelihood and severity of consequences
of all types of occupational PHs. This evaluation was aimed to carry out appropriate preventive
measures against all potential PHs [23,24] and is a necessary requisite in the workplace. Undeniably,
rehabilitation is complex, and medical and cognitive behavioral therapies are not always effective
against psychological disorders [25]. Depression, BOS, and PTSD have been characterized in highly
stressful jobs, such as military workers (both veterans and active duty service members), who face
challenging demands due to exposure to death and occupational traumas among others. PTSD is
particularly prevalent in militaries involved in war scenarios, and this diagnosis in U.S. military
workers varies widely from 10% to more than 30% [18,26
–
28]. In a cross-sectional study, Stern et al.
[29] observed that military veterans living with a dog increased their feeling of calmness and
decreased loneliness, depression, and worries about their own and the family’s safety.
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Accumulating research evidence indicates how the presence of animals can play a positive role
in helping people improve their quality of life, and with the implementation of AAIs symptoms
related to mental health problems in both youth and adults can be reduced [30
–
32]. The inclusion of
animals in psychological treatment is neither new nor peculiar. The first report dates back to the late
18th century when animals were brought into psychiatric institutions to promote and enhance the
socialization of patients [33]. Several studies indicate that animals can act as safe caregivers or
primary social supports, providing a sense of purpose that is recognized as a protective factor in
existing suicide and mental health research [34,35].
In particular, the use of AAI for the treatment of trauma is increasing. One previous systematic
review [36] observed that AAIs provide improvements in several areas among people suffering from
symptoms of trauma they have experienced: Acting as social facilitators to connect people and reduce
feelings of isolation and loneliness; reducing symptoms of hyperarousal, anger, anxious thoughts,
emotional numbing, and depression while improving positive emotions; enabling people to stay in
the present; reducing fear of public spaces; and promoting the production of oxytocin [37,38] and the
reduction of stress-related biological parameters, such as cortisol, heart rate, and blood pressure [38].
Many of the problems listed are still relevant to military veterans today, which is why the use of AAI
has begun [39].
Members of the military have a long tradition of working with animals. They are a source of
pride in the form of mascots, have specific tasks that help soldiers, can relieve stress, and increase
humility during difficult times, and are now associated with an easier transition to civilian life after
service [39,40]. The use of companion animals for military veterans is a relatively new area of research
but builds directly on the growing evidence base showing that animals-particularly in the assistance
role can positively influence the management of symptoms associated with PTSD and improve
overall well-being [41
–
43].
Military and veterans who work with animals specifically trained to manage PTSD through
specific supportive behaviors (e.g. waking someone from a night terror, acting as a sentinel in public,
helping to self-regulate anger or grief) report that this complementary treatment leads to greater
composure, more positive affect, and reduced feelings of nervous system overexcitement and states
of hypervigilance [44]. Chalmers and Dell [45] described AAI for veterans with PTSD as an important
source of individual support and complementary treatment to improve veterans' overall well-being.
Treatment of PTSD through the implementation of AAI is still in the early stages of empirical
research, but existing studies show promising results [39,46
–
50]. Gillett and Weldrick [46] identify
three specific areas of benefit: biomedical, psychological, and social. Examples of direct effects
include improved physiological markers, such as decreased anxiety and blood pressure, and
increases in oxytocin (the "feel good" hormone) [51]. Indirect effects result from everyday social
interactions that can positively impact overall health, for instance, walking the dog to exercise and
reducing social isolation or loneliness [52]. O-Haire et al. [36] observed that satisfaction with the
quality of life of military veterans returning from a deployment can be improved even though an
increased self-efficacy in coping with stressful life events, reduced fear of public spaces, decreased
anger, and increased levels of well-being.
Most PTSD treatment is fraught with the stigma associated with a military member seeking
treatment for internalized fears or emotional pain. The use of AAI offers a potential treatment
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pathway with relatively little stigma and an option being viewed as acceptable by veterans
themselves [39]. In addition, the demonstrated reduction in PTSD symptoms, reduction in
depression, and increase in overall quality of life are necessary elements of suicide prevention. Given
the strong correlation between suicidality and the affective states associated with PTSD [53], animals
keep their veterans company and become surrogate caregivers within their family unit. This secure
attachment is similar to that between humans and is one of the most important factors in suicide
prevention.
A 2016 systematic review on the effects of AAI on trauma supported short-term, subjective
benefits of AAI for trauma, including reduced depression, PTSD symptoms, and anxiety. However,
effect sizes ranged from small to large, and intervention procedures and research designs varied
greatly, evidencing the preliminary nature of research in this area [36]. Therefore, the aim of the
current review was to systematically investigate the benefit of pet ownership and animal-assisted
support programs among active-duty military workers and veterans affected by PTSD or post-
traumatic stress symptoms.
METHODS
Criteria for study inclusion and search strategy
A systematic review was conducted in December 2021 and June 2022 to provide insight into the
beneficial effects of pets’ presence in an occupational military context. The study protocol for this
review was registered at PROSPERO on 13 December 2021 under the following registration number:
CRD 298027. We conducted a comprehensive search of the literature in the databases of Scopus,
PubMed/Medline, and WOS. The search strategy was based on the combination of the following
search terms: “veterans OR military”, “pets OR companion animals”, “dogs”, “canine”, “equine”,
“animal-assisted therapy”, “animal-assisted intervention”, “animal-assisted activity”, AND
“delayed stress syndrome”, OR “post-traumatic stress”, OR “Post-traumatic Stress Disorder” OR
“PTSD”. References of the identified papers (citation searching) were also assessed for retrieving
additional studies.
Study selection
This study was conducted according to the Preferred Reporting Items for Systematic Review
and Meta-Analyses (PRISMA) 2020 guidelines [54]. As we aimed to identify prevalence data, the
search strategy was focused to identify articles with quantitative approaches, excluding qualitative
or mixed method research, case reports, narrative or systematic reviews, meta-analyses, study
protocols of RCT, letters to the editors, and commentaries. We included all studies that investigated
the effect of the presence of animals in the military context: at work, during the military operation, in
health recovery centers, where veterans with PTSD were treated for rehabilitation. We included all
studies involving the interaction between military workers/soldiers or veterans with PTSD and any
type of human-animal interaction (HAI) (i.e., dogs, cats, pinnipeds, horses), for the preventive
purpose of reducing occupational stress or alleviating PTSD symptoms and facilitating recovery. All
papers that have exclusively studied the impact of HAI on military workers’ psychological health,
including work-related stress, distress, and burnout, were excluded for the purposes of this review.
Also, we considered studies investigating whether owning pets or pets’ attachment outside the
workplace could help military workers manage PTSD symptoms, regardless of the presence of
animals at work as eligible. Studies that adopted physiological markers i.e. salivary cortisol, alpha-
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amylase to monitor stress reaction among soldiers, or change in pharmacological treatment as
indirect signs of mental health recovery were also included.
Only articles written in English from January 2001 to December 2021 were included. We
excluded studies carried out on non-occupational cohorts or those describing AAIs for disabled or
chronically ill people. Similarly, we excluded studies that investigated the effect of the intervention
with animals on outcomes other than PTSD and those addressing whether human-animal interaction
at work may facilitate the execution of challenging tasks outside the workplace. Also, we excluded
all articles concerning AAIs or AATs in other categories of workers (healthcare, social, office workers,
etc.), and studies examining the presence of animals in the workplace without therapeutic purposes.
Finally, studies examining the knowledge or attitudes of workers towards AAIs were excluded.
Two authors (FC and IC) independently screened all records identified as a result of search to
identify eligible titles and abstracts. We conducted the full-texts screening to determine their
inclusion in this review. In case of disagreements, a third reviewer (DAM) was consulted to build
consensus and taking final decisions. Figure 1 shows a flow diagram of the literature search strategy
and the review process.
Data collection process
Retrieved data were exported to Microsoft Excel (Microsoft Corporation, 2018). Data were
extracted in a standardized form and included elements, such as source (first author and year of
publication), study location and design, study population and instrument, type of
intervention/exposure, and main findings on PTSD and other psychological effects including
depression, quality of life and others, as the secondary outcome (Table 1). The results of the studies
were analyzed qualitatively (narrative synthesis) and where possible, also quantitatively for meta-
analysis. The findings obtained were discussed by all the authors. An exploratory meta-analysis was
performed for intervention studies of veterans experiencing PTSD or PTSD-related symptoms
receiving an AAI intervention compared to either AAI waitlist or standard psychotherapeutic care.
Most studies included in this systematic review performed within-subjects, longitudinal designs and
could not be synthesized through meta-analytic procedures due to the large heterogeneity (and
inflated error) between study designs and endpoints. Since limited studies (n = 4) were included in
the meta-analysis, an explanation of the methods and results of the meta-analysis is detailed in the
supplementary materials.
Study quality assessment
The assessment of study quality was carried out with a 16-item Quality Assessment Tool for
Studies with Diverse Designs (QATSDD) [55]. This tool has good reliability and validity for use in
the quality assessment of diverse studies in a wide variety of health fields including psychology,
allied health, medicine, public health, nursing, health services, and social sciences. The QATSDD
contains 16 reporting criteria scored on a scale from 0 to 3 (Not at all/Very
slightly/Moderately/Complete) [55].
RESULTS
Description of the studies included
The literature search yielded 3,148 published references. After review of the title, abstract and
full text, a total of 25 studies met the inclusion criteria and were reviewed (Figure 1). Almost all the
included studies were published between 2017 and 2022, except for one published in 2014 [56]. In an
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analysis by country, we found that majority of the studies included were carried out in the USA (n
=22), except for three studies being conducted in Denmark [60], Australia [72], and Israel [75]. All
publications used a quantitative approach, as illustrated in Table 1. The majority of the studies
utilized longitudinal designs (n=23) to analyze the effects of AAI (service animals training programs)
among military veterans affected by PTSD (n =24) and military dog handlers (n=1). Only two studies
[66, 68] were cross-sectional in nature.
The quality assessment of this review showed high-quality
scores for the majority of the articles being included in this review.
Most of the AAIs were canine-assisted programs (n=12) [48,57,58,60-62,65-68,70,76,78]) and
therapeutic horseback riding or equine-assisted psychotherapy (n=11) [56,59,64,71-75,77-79]). Only
one study was based on a pinnipeds-based program [69]. One was based on several types of animals
[63].
Most of the studies (n= 17) used the Posttraumatic Stress Disorder Checklist (PCL) in its various
versions, three used self-reported measures of PTSD and the CAPS tool, two studies the CAPS and
SCID-5 in combination, and one study the revised Trauma Symptom Inventory 2 (TSI-2), and one
study used the SPRINT Scale or the Mississippi Scale for Combat-related PTSD. Most of the studies
(n=18) observed significantly lower PTSD symptomatology after AAI. Three studies observed no
statistically significant differences in PTSD symptomology. Four studies investigated the effects of
AAI on other positive and negative psychological outcomes like increased perceived stress [57,58],
isolation and self-judgment and increased self-compassion [58], resilience [59], and subjective well-
being [60].
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Figure 1. Flowchart detailing selection and screening of the studies included in this review.
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Table 1. Studies on the effects of AAIs in military/veterans (n =25).
Authors
and year
Cou
ntry
Study design Study population Type of AAI Measures of
PTSD
Score Main findings
Arnon et al,
2020 [71]
Beetz et al,
2019 [57]
USA
USA
Longitudinal
(Before-after
study)
Longitudinal
(NRCT)
8 Military
Veterans
with PTSD
60 Military dog
handlers (29 AAI
group vs 31 “no
dog” group)
EAT (eight
weekly 90-
min
sessions)
DTP (1 week
for 4 weeks)
PCL-5, CAPS-
5
Self-reported
questions
about
trauma
confrontation
during trauma
therapy
39
39
Significant improvement
in PTSD symptoms
severity(CAPS-5) pre to
post treat (t = 9.58, p <
0.001, d = 1.49) mid-point
to post-treat (t = 2.70, p =
0.035, d = 0.54) and pre-
treat to follow -up (t =
3.35, p = 0.020, d = 1.60)
and in pre to post-treat
(PCL-5) (t = 3.80, p =
0.009, d = 1.63)
No significant difference
in PTSD symptoms
severity, perceived
stress, or functional
problems
with emotions and
actions due to the PTSD
and therapeutic alliance
between the two groups.
A weekly questionnaire
revealed that AAI
increases subjective
well-being, in particular
happiness.
Bergen-Cico
et al, 2018
[58]
USA Longitudinal
(NRCT)
45 Military
veterans
(31 AAI group vs
14 “no dog”
group)
DTP
(90-minute
weekly for
12-18
months)
PCL-M 39 Veterans participating in
the Dogs2Vets owner-
trainer program
experienced significant
reductions in symptoms
of post-traumatic stress
(p =0.01), perceived
stress (p < 0.001),
isolation, and self-
judgment (p =0.002)
accompanied by
significant increases in
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Authors
and year
Cou
ntry
Study design Study population Type of AAI Measures of
PTSD
Score Main findings
self-compassion (p
<0.001).
Burton et al,
2019 [59]
USA Longitudinal
(NRCT)
21 Military
veterans with
PTSD:
10 subjects
received EAP vs 11
subjects treated
with standard care
EAP
(1 week for 6
week)
PCL-M 39 PTSD symptom severity
was significantly
reduced within both
groups during the 6-
week study period
(p<0.05) ; a significant
increase in resilience in
the EAP group (p =
0.0268)
Duncan et
al, 2014 [56]
USA Longitudinal
(Before-after
study)
31 Military
veterans
with PTSD
EAL Self-reported
symptoms of
PTSD
35 87.1% of veteran
participants reported
“very positive perceived
benefit” regarding relief
from their PTSD
symptoms.
Farmer, 2021
[63]
USA Longitudinal
(Before-after
study)
20 Military
veterans (14 with
PTSD, 6 without
PTSD)
DTP
(1 month for
three
months)
PCL-5 38 A no statistically
significant (p=0.11)
reduction in PTSD
symptoms pre (mean
51.25 ± 13.79) and post
(mean 48.65 ± 14.72) AAI
was reported.
Fisher et al,
2021 [73]
USA Longitudinal
(NRCT)
63 Military
Veterans
with PTSD
EAT (eight
weekly 90-
min
sessions)
PCL-5, CAPS-
5
(pretreatment,
midpoint,
post-
treatment, and
follow-up)
39 Significant improvement
in PTSD symptoms
severity, assessed by
CAPS-5, pre to post treat
(p < 0.0001, d = 1.11)
which persist at 3-month
follow-up (p=0.88) and
assessed by PCL-5 (p <
0.0001, d = 1.05)
Galsgaard
and
Eskelund,
2020 [60]
Den
mar
k
Longitudinal
(Before-after
study)
4 Military veterans
with PTSD
DTP
(weekly
group
sessions)
PCL-C 38 AAI led to a substantial
reduction in PTSD
symptoms measured in
2 cases. In two cases,
similar levels of PTSD
symptoms were
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Authors
and year
Cou
ntry
Study design Study population Type of AAI Measures of
PTSD
Score Main findings
measured before and
after the intervention.
Johnson et
al, 2018 [64]
USA Longitudinal
(RCT)
29 military
veterans with
PTSD:
AAI group (n=15)
vs “no dog” group
(n=14)
THR PCL-M 39 AAI group reported
lower PTSD symptoms
after 3 weeks of AAI
(P ≤ 0.01) as well as a
clinically significant
decrease after 6 weeks
(P ≤ 0.01) than the “no
dog” group.
Kloep et al,
2017 [78]
USA Longitudinal
(before-after
study)
12 Military
veterans
with PTSD
(1
st
cohort n=7 2
nd
cohort n=5)
AAT (dogs) PCL-S 39 Significant improvement
in PTSD symptoms
severity, pre to post-
treat (p < 0.001) Results
indicated that 100% of
the current sample
achieved clinically
significant change
in PTSD symptoms at 6-
month follow-up.
Krause-
Parrello et
al, 2019 [65]
USA Longitudinal
(RCT)
120 military with
PTSD:
AAI group (n=60)
vs “no dog” group
(n=60)
DTP PCL-M
39 AAI group experienced
greater decreases
in stress, as measured by
cortisol than controls
(p<0.05). AAI group
with higher PTSS had a
greater reduction in
stress assessed with IgA
compared with those in
the control group.
Lanning et
al, 2017 [77]
USA Longitudinal
(before-after
study)
39 Military
Veterans
with PTSD
THR (8-
week)
PCLM, PCL-5 39 Improvement in PTSD
symptoms pre-post
treatment with PCL-5 ( g
= -1.15 95%CI: -1.71 to -
0.59) and PCL-M (g =-
1.76, 95%CI: 3.46 to -
0.05).
Malinowski
et al, 2018
[74]
USA Longitudinal
(NRCT)
7 Military
veterans
with PTSD
EAAT (five
consecutive
PCL-5 39 Significant overall
reductions in PTSD
symptoms pre to post-
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Authors
and year
Cou
ntry
Study design Study population Type of AAI Measures of
PTSD
Score Main findings
daily
sessions)
treatment (p=0.049) and
specifically in significant
reductions in
Cluster E Hyperarousal
Symptoms (p=0.037)
Miller et al,
2018 [76]
USA Longitudinal
(before-after
study)
31 Military
veterans
with PTSD
DTP CAPS-5, SCID
(DSM5)
39 Non-significant
protection effect given
by the presence of
canines in reducing
nightmares (OR =0.75
95%CI 0.47-1.18 p 0.21)
O'Haire and
Rodriguez
2018 [48]
USA Longitudinal
(NRCT)
141 Military
veterans with
PTSD:
usual care plus
AAI group (n = 75)
vs controls/usual
care group (n = 66)
DTP PCL 39 AAI group reported
lower PTSD symptoms
during follow up with
large effect sizes (after 3
weeks: p < .001, d =
−2.11, follow-up: p <
.001, d = −1.03),
depression (p < 0.001),
improvement in quality
of life (p < 0.001) and
social functioning (p <
0.001) than usual care
group.
Rodriguez et
al, 2018 [61]
USA Longitudinal
(NRCT)
73 Military
veterans with
PTSD:
AAI group (n=45)
vs controls/no dog
group (n=28)
DTP PCL, cortisol
salivary
measurement
39 AAI group showed a
higher cortisol
awakening response
(AUCi p=0.03; CAR
p=0.02) compared to
waitlist controls
Rodriguez et
al, 2021 [66]
USA CS
129 Military
veterans with
PTSD:
AAI group (n=67)
vs controls/no dog
group (n=62)
DTP PCL-C.
Self-reported
questions on
PTSD
medication
39 AAI group reported
lower PTSD symptom
severity (p < 0.001) and
often a change
(decreased dose) or
discontinuation in
psychiatric therapy
(p<0.001) since getting
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164
Authors
and year
Cou
ntry
Study design Study population Type of AAI Measures of
PTSD
Score Main findings
their service dog than
the “no dog” group.
Romaniuk et
al, 2018 [72]
Aust
ralia
Longitudinal
(Before-after
study)
25 Military
veterans
with PTSD
EAT PCL-5 39 Significant improvement
in PTSD symptoms
severity (PCL-5) pre to
post treat (t = 3.92, p <
0.017, d = 0.88) and post-
treat to follow -up (t = -
3.49, p = 0.017, d = -1.16)
Scotland-
Coogan et
al, 2020 [68]
USA CS 71 Military
veterans with
PTSD
DTP Self-reported
questionnaire
PTSD
symptoms
39 AAI led to a reduction in
self-disturbance, PTSD,
externalization, and
somatization and
improved interpersonal
difficulties and suicidal
ideation.
Shelef et al,
2019 [75]
Israe
l
Longitudinal
(NRCT)
13 Military
with PTSD
EAT
(weekly 180-
min sessions
for 6
months)
SPRINT scale 39 Significant overall
reductions in PTSD
symptoms pre to post-
treatment (d=-2.85 ± 4.14
p<0.05)
Steele et al,
2018 [79]
USA Longitudinal
(before-after
study)
85 Military
Veterans
with PTSD
EAP Mississippi
Scale for
Combat-
related PTSD
38 Significant improvement
in PTSD symptoms
severity, pre to post treat
(p < 0.001, d = −0.70)
Whitworth
et al, 2019
[67]
USA Longitudinal
(NRCT)
45 Military
veterans with
PTSD:
AAI group (n=15)
vs controls/no dog
group (n=30)
DTP TSI-2 39 AAI group reported
lower self-disturbance (p
< 0.05), post-traumatic
stress symptoms (p <
0.05), and
externalization (p <
0.05), depression (p <
0.05) and anger (p <
0.05) than “no dog”
group.
Woodward
et al, 2021
[62]
USA Longitudinal
(Before-after
study)
54 Military
veterans with
PTSD
DTP SCID-5,
CAPS-5,
PANAS
39 Veterans reported lower
PTSD severity (effect = -
0.32, CI (99.3%) =
-0.40 to -0.23)
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165
Authors
and year
Cou
ntry
Study design Study population Type of AAI Measures of
PTSD
Score Main findings
Wortman et
al, 2018 [69]
USA Longitudinal
(Before-after
study)
3 Military veterans
with PTSD
PTP PCL-5 38 Veterans reported lower
PTSD symptoms and
clinical improvement
after AAI.
Yarborough
et al, 2017
[70]
USA Longitudinal
(NRCT)
78 Military
Veterans
with PTSD;
Intervention
group AAI (n=24)
vs waitlist group
(n=54)
DTP PCL-M 38 Longitudinal assessment
compared mental health
and functioning within
individuals in the AAI
group indicated
significant improvement
in VR-12 mental
component summary
(p=0.008), BASIS
depression/functioning
Subscale (p=0.013),
BASIS emotional lability
subscale (p=0.003), PTSD
Checklist (p=0.001),
activity level (p=0.004),
happiness Score (p=0.01)
and quality
of life score (p=0.001)
Notes: AUCi,
Area under the curve with respect to increase;
CAPS-5, Clinician-Administered PTSD Scale-5; CAR,
Cortisol awakening
response in μg/dL;
EAL, equine-assisted learning program; EAP, equine-assisted psychotherapy; EAT, equine-assisted therapy;
EATT, Equine-Assisted Activities, and Therapies;
DTP, dog training program PCL-C, Posttraumatic Symptom Checklist,
Civilian version; PCL-M, PTSD Checklist Military Version; PCL-5, Posttraumatic Checklist 5; RCT, randomized clinical trial;
SCID-5, Structured Clinical Interview for DSM-5;
TSI, 136-item Trauma Symptom Inventory-2; THR, therapeutic horseback
riding; PTP, pinnipeds therapy program, NRCT, Non-randomized Clinical trial (Quasi-experimental study); CS, Cross-
sectional study. SPRINT, Short Post Traumatic Stress Disorder Rating Interview
Effects of AAI with dogs in military workers and veterans
Most of the studies in our review pointed to the helpful effects of service dogs as a
complementary treatment for PTSD in military workers and veterans. However,in our meta-analysis
findings, we did observe a non-significant reduction in PTSD symptoms for veterans engaged in AAI
programs compared to waitlist controls or standard psychotherapeutic care. The dog-assisted
programs were offered in two different forms, including training and playing activities (sessions
included walking, different play and grooming activities with dogs and just relaxing together toward
the end) [57] and were performed with the aid of both dog-owning participants or dogs specifically
trained for these tasks.
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O’Haire and Rodriguez [48] demonstrated lower levels of depression and improvement in
quality of life and social functioning in the treatment group. Galsgaard and Eskelund [59] observed
a reduction in depression and distress symptoms and increased ability to control daily life problems,
such as disturbed sleep, social isolation, physical inactivity, lack of emotional regulation and
increased quality of life. Rodriguez et al. [61] found that AAI group reported lower anxiety (p<0.001),
anger (p<0.01), sleep disturbances (p<0.01), and alcohol abuse (p < 0.05) than the “no dog” group.
Woodward et al. [62] showed a reduction in negative affect and an increase in positive affect.
In two studies, participating in a service dog training program was, therefore, proven to be effective
in ameliorating psychiatric symptomatology (self-disturbance, posttraumatic stress, externalization,
somatization, lack of emotional regulation), depression, social isolation, and quality of life of veterans
suffering from PTSD [60,68]. In another study, in contrast to a group of veterans receiving usual care,
the dogs’ group resulted in lower PTSD symptoms after receiving a service dog (p < 0.001), as well as
in the higher quality of life (p < 0.001), less depression (p < 0.001) and better social functioning (p <
0.001) [48]. Comparing military veterans with PTSD, who completed service dog programs and
veterans on a waitlist, Whitworth et al. (2019) [67] observed that the former group experienced a
significant decrease in a broad scope of psychological symptoms associated with PTSD posttraumatic
symptomatology, in persistent intra/interpersonal difficulties associated with psychological trauma,
and in disabilities secondary to their PTSD. Similarly, the study of Krause Parello (2019) [65]
supported AAI as a stress-reducing modality in aeromedical evacuation military patients, assessed
by physiological biomarkers (cortisol, IgA, alpha amylase), particularly among those who reported
higher post-traumatic stress symptoms severity (PTSSS).
In the study by Yarborough et al. [70], a service dog led to a significant improvement in PTSD
symptoms severity, psychological well-being, and social functioning. Interestingly, participants
indicated specific behavioral tasks performed by the dogs that help them to control PTSD symptoms.
These tasks include preventing panic, waking veterans from nightmares, alerting veterans when
strangers are in the house, putting space between veterans and strangers, alerting veterans that
someone is approaching, and licking or nudging veterans to help them “stay in the present” when
they are experiencing distressing memories or flashbacks.
Service dogs reduced hypervigilance by alerting, creating boundaries, and disrupting
nightmares, improving sleep quality and duration. Dogs also helped veterans turn their attention
away from invasive trauma-related thoughts, improved their emotional connections with others,
increased their community participation and physical activity, and reduced suicidal impulses and
medication use. Living with a dog had a positive effect on anger, anxiety, sleep disturbance, and
alcohol abuse [61]. In the study by Withworth et al. [67], the AAI group reported lower self-
disturbance (p<0.05), posttraumatic stress (p < 0.05), and externalization (p<0.05), depression (p< 0.05)
and anger (p<0.05) than veterans from group without treatment. In the study by Rodriguez et al. [66],
the AAI group reported lower PTSD symptom severity (p<0.001) and often a change or
discontinuation in psychiatric therapy (p<0.001) since getting their service dog than the “no dog”
group. Conversely, no significant advantage of the dog-assisted intervention regarding PTSD
symptom severity, perceived stress, and functional problems with emotions and actions due to the
PTSD was observed in the dogs group in comparison with the control group who received standard
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treatment in the studies conducted by Beetz et al. [57] and Farmer [63]. However, it was found in the
AAI group an improvement in work and social adjustment [57].
Finally, Woodward et al. [62] observed that engagement with a service dog was associated with
significant reductions in negative affect and an increase in positive affect (p<0.001) in a group of 54
military veterans with PTSD.
Effects of AAI with equine and other animals in military workers and veterans
Regarding equine-assisted interventions (EAI), studies obtained mixed results. In contrast to a
group of veterans receiving usual care, veterans who have been engaged or involved in therapeutic
horseback riding (THR) showed a significant reduction in PTSD score after 3 weeks of THR (p≤ 0.01),
which was associated with a clinical improvement of PTSD syndrome after 6 weeks of THR (p≤ 0.01)
[64]. On the contrary, participating in a 6-week EAP program did not produce a statistically
significant difference with respect to PTSD symptomatology and perceived stress level, when
measured by salivary cortisol level [59]. A single study focused on pinniped HAI program for
veterans identified as having PTSD-like symptoms.
Arnon et al. [71] studied the effect of EAT (equine-assisted therapy) on a group of 8 veterans
with PTSD diagnosis. They reported that group EAT for veterans with PTSD appeared safe,
satisfying, and well-attended; veterans experienced marked clinical improvement in PTSD symptoms
severity in the short term although short-term improvements seemed to be transient as they early
declined, with worsening symptoms for four of six patients assessed at 3-month follow-up. A
subsequent open trial conducted on a relatively large sample of military veterans with clinician-rated
and self-report outcome measures of PTSD confirmed the evidence that EAT intervention for PTSD
produces clinical benefits by reducing PTSD symptoms severity and in some cases leading to a
reduction below the cut-off score for PTSD diagnosis in CAPS-5 questionnaire. This clinical
improvement largely persisted for three months following treatment. The pilot study of Duncan et
al. [56] on EAT carried out on 31 veterans diagnosed with PTSD utilized a self-report measure
developed by the researchers, which included the sub-scales relieving symptoms of PTSD subscale
to assess change in PTSD symptoms severity. The study found that 87.1% of veteran participants
reported “very positive perceived benefit” regarding relief from their PTSD symptoms. Similarly,
Romaniuk et al. [72] observed a “clinically significant change” in terms of PTSD symptoms from pre-
EAT intervention to post-EAT intervention in a group of 25 Australian military veterans, although
this improvement was not maintained at follow-up. Military veterans engaged in EAAT program for
five days reported a significant decrease in all symptoms clusters of PTSD and noteworthy cluster
and hyperarousal symptoms were significantly reduced [74].
Shelef et al. [75] also reported a significant decrease in PTSD symptoms in Israelian soldiers with
PTSD after six months EAT program; particularly the higher statistically significant improvement
was recorded in functioning domains of the SPRINT scale such as the ability to work and perform
daily tasks. Lanning et al. [77] recruited 39 combat veterans who completed an 8-week study of THR
and reported on improvement in PTSD symptoms, social functioning, and reduced interference of
emotions in daily activities. In the study of Steele et al. [79], military veterans with PTSD experienced
statistically significant and substantive improvement in PTSD symptomatology after participating in
an equine-assisted psychotherapy program.
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DISCUSSION
This systematic review aimed to examine the effects of AAI on the psychological well-being of
military workers and veterans. The studies included in this work demonstrated the relevant role of
AAI, such as rehabilitation programs to support military workers and veterans affected by PTSD
symptoms. We found 25 studies [48,56
–
61,63
–
79] that examined whether AAIs can help military
service workers and veterans cope with psychiatric symptoms, including PTSD symptoms, and
improve their social and occupational functioning. The AAIs were also able to help build positive
relationships with veterans that help them cope with military-associated trauma reactions. Providing
service dog programs for these veterans has been one of the most successful methods of coping with
their psychiatric difficulties. In the United States, where most of the studies were conducted, a service
dog is defined under the federal Americans with Disabilities Act (ADA) as “any dog that is
individually trained to do work or perform tasks for the benefit of an individual with a disability,
including a physical, sensory, psychiatric, intellectual or other mental disability” [80]. The work a
dog performs must be directly related to the person's disability. There are rehabilitation strategies,
including canine-assisted therapies and rehabilitation activities that use dogs as an adjunct to
therapy. Examples include guiding the blind, pulling a wheelchair, alerting a person who is hard of
hearing, protecting a person experiencing a seizure, and calming a person with PTSD during an
anxiety attack or psychiatric episode [81,82].
Canine-assisted therapies and activities have been practiced in rehabilitation facilities for some
time [81,82]. This review shows that service dogs and horses can be useful support for veterans with
PTSD. The animals can be individually trained to perform work or tasks that help a person with a
mental disability. In addition, pet ownership may be a protective factor against self-harm thoughts
in veteran groups [83]. Mental illnesses, especially those following polytraumatic events such as
PTSD, are challenging to treat, so they may benefit from complementary therapeutic approaches that
include AAIs [84]. There is limited literature on the positive effects of dogs and horses before and
during the onset of traumatic events in veterans. However, our study shows that AAI could integrate
traditional therapies such as prolonged exposure therapy (PE), cognitive processing therapy (CPT),
eye movement desensitization, and reprocessing (EMDR) in combination with
psychopharmacological medications in veterans with PTSD [67,85].
The U.S. Army Medical Department also published some very limited data suggesting that AAT
may benefit wounded warriors participating in a life skills program and supports the need for further
research in the area of AAT as adjunctive therapy for veterans with PTSD and other traumatic
injuries, including traumatic brain injury [86,87]. Several hypotheses could explain the benefits of
AAI in the psychological rehabilitation of veterans with mental health problems. Owen et al. [88]
described canine-assisted therapy as a useful complementary or alternative medical treatment for
veterans with PTSD based on a biopsychosocial concept. Yount et al. [89] argued that interactions
with dogs may increase oxytocin levels via neurobiological mechanisms that improve mental health
in veterans. Another possible mechanism by which dogs may have a positive impact on the mental
health of soldiers is by altering the human microbiome. This can be accomplished either through
direct interactions between the dog and the caregiver or through indirect effects, such as the dog's
contribution to the microbiome of the built environment [90]. Nearly 20 percent of military workers
returning from Iraq and Afghanistan-a total of 300,000-report symptoms of post-traumatic stress
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disorder or major depression, yet only slightly more than half have sought treatment (cRANDit.) [91].
Current treatment standards (e.g., exposure therapy, cognitive therapy) are limited due to their
availability, accessibility, and outcomes (e.g., retention, premature discontinuation, resistance,
nonresponse). In addition, inadequate staffing and training of mental health professionals exacerbate
pre-existing problems and challenges the quality of care provided to military workers. These
problems have led to the need to develop and refine alternative and complementary approaches to
provide more options and services to the military population. One such new approach is AAI as a
treatment option for veterans and returning military workers. It is important to note that despite the
positive research findings, AAI should be considered also from the animals’ well-being perspective
[92]. For example, some veterans have service-connected or otherwise acquired physical disabilities,
health problems such as allergies, or other safety issues such as fear of animals that may prevent them
from benefiting from this approach [93]. As with any type of treatment approach, veterans and
military workers must be fully informed about the potential risks and benefits of this intervention.
They should also be informed that although this form of treatment is becoming better evidenced, it
is not yet as established as other treatment modalities. Based on the current results, it appears that
veterans benefited from AAI and received an alternative treatment option, especially for those who
did not respond well to conventional treatments. The effects of AAI could be further explored to
better understand the unique characteristics, applications, and potential benefits of this intervention
for this specific population. Mental health professionals can collaborate with organizations that
provide AAI as a treatment for returning veterans and military workers struggling with war stress
injuries to improve the overall quality of life. Continued development of standardized curricula,
therapeutic practices, evaluation measures, and guidelines will lead to a synthesis of the best
available evidence that will enable researchers, stakeholders, providers, and consumers to fund,
integrate, and recommend AAI for PTSD treatment.
This systematic review has some limitations. Many studies had small sample sizes in both
intervention and control groups and short duration of therapy sessions. Another limitation in the
quasi-experimental studies was the lack of a randomization schedule. Finally, causality and
directionality cannot be determined in the cross-sectional studies. Other limitations included the
diversity of interventions included (duration, interactions with animals, etc.), the diversity of samples
within studies (e.g., wide age range, differences in trauma, diagnosis/symptom presentation,
comorbidity), and the personnel who delivered the interventions.
However, our review has some strengths in that it adds to the body of knowledge about the
positive and negative aspects of animal presence in the workplace. This knowledge could be
considered by military organizations that intend to implement voluntary workplace health
promotion programs during service and after retirement based on pet-friendly policies. In addition,
some before-after studies reported that participants were used as their own control subjects to avoid
bias due to non-random assignment.
As indicated in our literature review, the psychological burden of PTSD in the U.S. military is
high, and social support from civilians and the home environment may play a greater protective role
in the long-term severity of PTSD symptoms [92,93]. Although practicing yoga and other spiritual or
mindfulness practices in the workplace may improve cognitive functioning (response inhibition)
related to PTSD symptoms, as well as other mental health outcomes, sleep hygiene and quality of life
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[94
–
97], and biological stress response in veterans diagnosed with PTSD [98], AAI may be beneficial
in military members affected by PTSD. Pets are a spiritual and physical resource [99], and severe
psychological trauma can lead to loss of faith and struggles in the spiritual realm, resulting in
increased suicide risk [100
–
104]. Therefore, further research on the psychological effects of AAI
associated with mindfulness and spiritual activities in occupational health services could be planned
to provide early diagnosis and treatment of PTSD symptoms in both military veterans and active
duty service members.
CONCLUSION
In conclusion, this review showed that AAI in the workplace, especially in dogs, may
positively impact on mental well-being of military workers and promote the recovery of veterans
affected by PTSD. Therefore, service dog programs can be helpful as complementary or alternative
treatment options for some veterans. However, AAI programs need to be investigated to better
characterize and understand the benefits and limitations of their inclusion in military workers and
veteran rehabilitation. Longitudinal studies in the context of mandatory occupational health
surveillance programs could be the ideal setting to understand better the effectiveness of these dog
service programs on the mental well-being of military workers. Finally, future studies should also
investigate the possible negative effects of pet ownership in the workplace and the possible
implications for co-workers and employers.
Author Contributions: Conceptualization, study design, methodology, formal analysis, writing- original draft,
writing- review & editing: FC, IC, DAM, Search of articles: FC, IC. Data collection, writing- review & editing: B
B-K, MP, LS, GN, B N-K. Statistical analysis and meta-analysis: AH. Resources, and supervision: GF,CGG, MMG,
DAM. Supervision, formal analysis, writing- review & editing: KB, MS.
Funding: None
Acknowledgments: None
Conflicts of Interest: None
Data Availability Statement: Some or all data and models that support the findings of this study are available
from the corresponding author upon reasonable request.
Publisher’s Note: Edizioni FS stays neutral with regard to jurisdictional claims in published maps and
institutional affiliation.
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Supplementary Materials
Meta-analysis
Methods: The exploratory meta-analysis was performed on intervention studies of veterans experiencing PTSD
or PTSD-related symptoms receiving an AAI intervention compared to either AAI waitlist or standard
psychotherapeutic care. We included data from four studies on the basis that they had published sample size,
mean, and standard deviation of PCL-M (PTSD checklist, military version) scores for both groups at pre-
intervention and post-intervention time points. Pre- and post-intervention data were compared at baseline and
intervention endpoint only, we did not analyze the longitudinal follow up period. For Johnson et al. (2018), we
extracted data from both groups after week 3 of the intervention because after week 3 the controls were invited
to participate in the intervention. The studies included are detailed in Supplementary Table 1. Meta-analytic
procedures were performed using “metafor" version 3.4-0 (Viechtbauer, 2010) package within R version 4.2.1
(2022/06/23) GUI 1.72 for Mac (Core Team R, 2021). Hedge’s g effect sizes, including variances and 95%
confidence intervals were calculated. Hedge’s g was calculated by computing a standardized effect size for pre-
intervention and post-intervention for both group using the approach described by Morris (2008).
Given the
diversity of interventions compared, a restricted maximum likelihood method (REML) was used to fit the meta-
analytic model.
The value of Hedge's g is < 0 when there is a reduction of PTSD symptoms in the intervention
group compared to the AAI waitlist or standard psychotherapeutic care at the end of the intervention. Effect
sizes were interpreted using Cohen’s (1988) guidelines of 0.2 = small, 0.5 = medium, and 0.8 = large.
Heterogeneity between studies was assessed using the Q and I
2
statistic (Higgins et al. 2003). A significant Q
statistic indicates between-study heterogeneity that may be influenced by moderating variable; however, in this
analysis, we had a small sample size that could make heterogeneity uninterpretable. Estimated I
2
was interpreted
as <30% = low heterogeneity, ≥ 31% and ≤ 60% = moderate heterogeneity, and ≥ 61% = high heterogeneity.
Findings: The calculated mean effect size for change in PTSD symptoms was not significant when
comparing veterans in AAI interventions to AAI waitlist or standard psychotherapeutic care (g = -0.76, z = -1.56,
95% CI: -1.71 – 0.19, p = 0.194). There was a moderate effect and a non-significant reduction observed in PTSD
symptoms with veteran engagement in animal-assisted interventions in the meta-analysis model. Heterogeneity
was large and significant (Q(3) = 35.98, p < 0.001, I
2
= 89%).
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EDIZIONI FS Publishers
179
Supplementary Table 1. A summary of the studies included in the meta-analysis
Study Design Animal AAI Length Format Diagnosis Sample Size Mean Age
(SD)
Contrast
Bergen-Cico et al.
(2018)
NRCT Canine
CAP 90 min weekly for
12-18 months
Individual PTSD
(DSM-V)
Intervention:
n = 31
Control:
n = 14
Intervention:
41 (12)
Control: 43
(11)
Dogs2Vets vs Waitlist
Control
Burton et al. (2019) NRCT Equine EAP 1 hour weekly for 6
weeks
Group PTSD
(DSM-V)
n = 10/group, sex-
matched (8M/2F)
Intervention:
48 (15)
Control: 46
(13)
EAP vs Standard Care
Johnson et al. (2018) RCT Equine EAP 1 hour weekly for 6
weeks
Group PTSD
(DSM-V)
n = 32 (32M/6F) Full sample: 54
(13)
EAP vs Waitlist
Control
O'Haire and
Rodriquez (2018)
NRCT Canine CAP 3-week group class Group PTSD
(DSM-IV)
Intervention:
n = 75 (60M/15F)
Control:
n = 66 (50 M/16F)
Intervention:
37 (9)
Control: 37 (8)
CAP vs Waitlist
Control
Note. NRCT = non-randomized control trial, RCT = randomized control trial, EAP = equine-assisted program, CAP = canine-assisted program, PTSD = post-traumatic stress disorder, M
= male , F = female , SD = standard deviation
EDIZIONI FS Publishers
180
Supplementary Figure 1. A forest plot of the standardized effect size for pre-intervention and post-intervention comparison of AAI intervention veterans vs AAI
waitlisted/standard psychotherapeutic care veterans. Effect sizes illustrated are Hedge’s g.
RE Model
-3 -2 -1 0 1
Observed Outcome
O'Haire and Rodriquez (2018)
Johnson et al. (2018)
Burton et al. (2019)
Bergen-Cico et al. (2018)
-2.03 [-2.55, -1.52]
0.10 [-0.40, 0.61]
-0.76 [-1.68, 0.17]
-0.32 [-1.02, 0.38]
-0.76 [-1.71, 0.19]
