Equine-assisted Therapy for Therapy-resistant Adolescents With Autism Spectrum Disorders, a Replicated AB-design
Phase: NA
Conditions: Emotion Regulation, Autism Spectrum Disorder, Adolescent - Emotional Problem
Sponsor: Karakter Kinder- en Jeugdpsychiatrie

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TEMPLATE RESEARCH PROTOCOL 
(September 2018) 
 
- 
May 2015: adaptation section 11.5: text in accordance to old and new Measure 
regarding Compulsory Insurance for Clinical Research in Humans  
- 
Sept 2015: adaptation section 9.1, 9.2 and 12.5: text in accordance to WMO 
amendment  on reporting SAE and temporary halt (section 10 of WMO) 
- 
Oct 2015: adaptation section 4.4 – comment [CCMO15], 8.2 and 10.1 with respect to 
methodology/statistics 
- 
Sept 2018: adaptation section 12.1 and comment [CCMO46] due to applicability 
GDPR as of May, 2018 
 
 
 

NL 77902.091.21 Pegasus 
 
 
 
 
PROTOCOL TITLE Pegasus: Equine-assisted Therapy for therapy-resistant adolescents 
with autism spectrum disorders, a multiple baseline ABA-study 
 
Protocol ID 
185 - 20 PEGASUS 
Short title 
Pegasus 
EudraCT number  
n/a 
Version 
1.0 
Date 
24-06-2021 
Coordinating 
investigator/project leader 
 
Drs. J.C. den Boer, Kinderpsychiater  
 
T: 0654310670  
E: j.denboer@karakter.com 
 
Karakter Kinder- en Jeugdpsychiatrie 
Postbus 68 
6710 BB EDE GLD 
Principal investigator(s) / 
multiple sites 
Prof. Dr. N. Lambregts-Rommelse, Klinisch 
neuropsycholoog/onderzoeker 
 
T: 024-3610655  
E: Nanda.Lambregts-Rommelse@radboudumc.nl 
 
Karakter, Kinder- en Jeugdpsychiatrie 
Postbus 68 
6710 BB EDE GLD 
 
Dr. A. Blonk 
T: 0620538996 
E: ablonk@gagelhoeve.nl 
Gagelhoeve 
Gagelweg 10 
5451 NE MILL 
 
E. van Noort 
T: 0681127700 
E: esther@horsesenco.nl 
Horses & Co 
Lindeweg 12 
2995 XK HEERJANSDAM 
 
 
Sponsor (in Dutch: 
verrichter/opdrachtgever) 
Karakter Kinder- en Jeugdpsychiatrie 
Postbus 68 
6710 BB EDE GLD  
Subsidising party 
ZonMw 60-63600-98-914 
Independent expert (s) 
Dr. W. Groen, w.groen@karakter.com 

NL 77902.091.21 Pegasus 
 
 
 
 
PROTOCOL SIGNATURE SHEET 
 
Name 
Signature 
Date 
Head of Department: 
 
Prof. dr. W. Staal 
Hoogleraar Kinder- en 
Jeugdpsychiatrie 
T: 024-3512222 
E: w.staal@karakter.com 
Karakter Nijmegen 
Universitaire Kinder- en 
Jeugdpsychiatrie 
Reinier Postlaan 12 
6525 GC NIJMEGEN 
 
24-06-2021 
Coordinating investigator/project 
leader 
 
Drs. J.C. den Boer, Kinderpsychiater  
 
 
 
Principal Investigator 
 
Prof. Dr. N. Lambregts-Rommelse, 
Klinisch neuropsycholoog/onderzoeker 
 
 
 
 
 

NL 77902.091.21 Pegasus 
 
 
 
 
TABLE OF CONTENTS 
 
1. 
INTRODUCTION AND RATIONALE .................................................................................. 9 
2. 
OBJECTIVES .................................................................................................................... 12 
3. 
STUDY DESIGN ............................................................................................................... 13 
4. 
STUDY POPULATION ...................................................................................................... 16 
4.1 
Population (base)....................................................................................................... 16 
4.2 
Inclusion criteria ......................................................................................................... 16 
4.3 
Exclusion criteria........................................................................................................ 16 
4.4 
Sample size calculation ............................................................................................. 16 
4.5 
Study population for the Qualitative study ................................................................ 17 
4.6 
Study population for the cost effectiveness study..................................................... 17 
5. 
TREATMENT OF SUBJECTS .......................................................................................... 18 
5.1 
Investigational product/treatment .............................................................................. 18 
6. 
INVESTIGATIONAL PRODUCT ....................................................................................... 20 
7. 
NON-INVESTIGATIONAL PRODUCT.............................................................................. 21 
8. 
METHODS......................................................................................................................... 22 
8.1 
Study parameters/endpoints ..................................................................................... 22 
8.1.1 
Main study parameter/endpoint.......................................................................... 22 
8.1.2 
Secondary study parameters/endpoints (if applicable) ..................................... 22 
8.2 
Randomisation, blinding and treatment allocation .................................................... 22 
8.3 
Study procedures for the randomized, multiple-baseline single-case design .......... 22 
8.4 
Study procedures for the qualitative study ................................................................ 27 
8.5 
Study procedures for the cost-effectiveness study ................................................... 28 
8.6 
Withdrawal of individual subjects .............................................................................. 29 
8.6.1 
Specific criteria for withdrawal (if applicable) ..................................................... 29 
8.7 
Replacement of individual subjects after withdrawal ................................................ 29 
8.8 
Follow-up of subjects withdrawn from treatment....................................................... 29 
8.9 
Premature termination of the study ........................................................................... 29 
9. 
SAFETY REPORTING ...................................................................................................... 31 
9.1 
Temporary halt for reasons of subject safety ............................................................ 31 
9.2 
AEs, SAEs and SUSARs ........................................................................................... 31 
9.2.1 
Adverse events (AEs)......................................................................................... 31 
9.2.2 
Serious adverse events (SAEs) ......................................................................... 31 
9.2.3 
Suspected unexpected serious adverse reactions (SUSARs) .......................... 32 
9.3 
Annual safety report................................................................................................... 32 
9.4 
Follow-up of adverse events ..................................................................................... 32 
10. 
STATISTICAL ANALYSIS ............................................................................................. 33 
10.1 
Study parameter(s) for the randomized, multiple-baseline single-case design ....... 33 
10.2 
Study parameter(s) for the qualitative study ............................................................. 33 
10.3 
Study parameter(s) for the cost-effectiveness study ................................................ 34 
10.4 
Mixed methods........................................................................................................... 34 
11. 
ETHICAL CONSIDERATIONS...................................................................................... 36 

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11.1 
Regulation statement................................................................................................. 36 
11.2 
Recruitment and consent........................................................................................... 36 
11.3 
Objection by minors or incapacitated subjects.......................................................... 36 
11.4 
Benefits and risks assessment, group relatedness .................................................. 36 
11.5 
Compensation for injury............................................................................................. 37 
11.6 
Incentives ................................................................................................................... 37 
12. 
ADMINISTRATIVE ASPECTS, MONITORING AND PUBLICATION .......................... 38 
12.1 
Handling and storage of data and documents .......................................................... 38 
12.2 
Monitoring and Quality Assurance ............................................................................ 38 
12.3 
Amendments .............................................................................................................. 39 
12.4 
Annual progress report .............................................................................................. 39 
12.5 
Temporary halt and (prematurely) end of study report ............................................. 39 
12.6 
Public disclosure and publication policy .................................................................... 39 
13. 
STRUCTURED RISK ANALYSIS ................................................................................. 41 
14. 
REFERENCES .............................................................................................................. 42 

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LIST OF ABBREVIATIONS AND RELEVANT DEFINITIONS  
 
ABR 
 
 
 
ASD 
General Assessment and Registration form (ABR form), the 
application form that is required for submission to the accredited 
Ethics Committee; in Dutch: Algemeen Beoordelings- en 
Registratieformulier (ABR-formulier) 
Autism Spectrum Disorder 
CCMO 
Central Committee on Research Involving Human Subjects; in 
Dutch: Centrale Commissie Mensgebonden Onderzoek 
CV 
Curriculum Vitae 
EAT 
Equine-assisted Therapy 
GCP 
Good Clinical Practice 
GDPR 
General Data Protection Regulation; in Dutch: Algemene 
Verordening Gegevensbescherming (AVG) 
IC 
Informed Consent 
METC  
Medical research ethics committee (MREC); in Dutch: medisch-
ethische toetsingscommissie (METC) 
(S)AE 
(Serious) Adverse Event  
Sponsor 
The sponsor is the party that commissions the organisation or 
performance of the research, for example a pharmaceutical 
company, academic hospital, scientific organisation or 
investigator. A party that provides funding for a study but does not 
commission it is not regarded as the sponsor, but referred to as a 
subsidising party. 
SUSAR  
Suspected Unexpected Serious Adverse Reaction 
UAVG 
Dutch Act on Implementation of the General Data Protection 
Regulation; in Dutch: Uitvoeringswet AVG 
WMO 
Medical Research Involving Human Subjects Act; in Dutch: Wet 
Medisch-wetenschappelijk Onderzoek met Mensen 
 
 

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SUMMARY 
 
Rationale: For people with autism spectrum disorder (ASD), daily life is highly stressful and 
traumatic with many unpredictable events that can evoke emotion dysregulation (ED): a 
strong difficulty with appropriately regulating negative affect. Heightened levels of ED may 
aggravate social dysfunctioning in ASD and vice versa. For a part of the patients with ASD, 
treatment as usual does not have any effect at all on ED. As ASD with severe levels of ED 
can be considered to have an ultra-high risk profile for developing other disorders (psychosis, 
anxiety, eating disorders, depression), this treatment-resistant subgroup of patients may end 
up needing life-long psychiatric treatment. Particularly problematic is that these patients often 
lack motivation for typically initiated forms of therapy, thereby further limiting their chances 
for a more favourable outcome. A highly promising method that may prove effective for 
therapy-resistant individuals with ASD is Equine-Assisted Therapy (EAT). While often met 
with prejudgment and skepticism, reports from parents and therapists as well as a recent 
systematic review suggest that EAT may have beneficial effects in youths with ASD. We 
further argue that an ideal (and perhaps last?) ‘window of opportunity’ for intervention in 
treatment-resistant patients with ASD is adolescence, because of the major genetically pre-
programmed neurological changes occurring in this period that heighten the sensitivity for 
environmental input. EAT targeting severe ED offered within this timeframe may improve 
clinical outcomes both in the short and in the long term in otherwise treatment-resistant 
adolescents with ASD. 
Objective: To quantify the short-term (15 weeks) and long-term (1 year) (cost-)effectiveness 
of Equine-Assisted Therapy (EAT) in adolescents with therapy-resistant ASD (aged 11-18) 
and, when proven (cost-) effective, implement EAT in clinical practice. 
Hypothesis: In a therapy-resistant group (N=35) of youths with ASD, a 15-week treatment 
with EAT significantly improves: 
1. the primary outcome measure emotion dysregulation in the short term  
2. secondary outcome measures of emotion dysregulation in the long term (1 year), ASD 
symptom severity, quality of life, self-esteem, global and family functioning and goal 
attainment as well as qualitative outcomes in the short term (15 weeks) and the long term (1 
year). 
3. is more cost-effective on the long term (1 year) when compared to continued CAU. 
Study design: Mixed-methods strategy consisting of three elements: a randomized, 
multiple-baseline single-case design (n=35), a qualitative study (n=8-10) and a cost-
effectiveness study (n=6).  
Study population: Treatment-resistant adolescents with ASD (11-18 years), with clinical 
levels of emotion dysregulation despite receiving care as usual (CAU) for at least 18 months  

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Intervention: 15 weekly sessions of 60 minutes EAT using a standardized protocol by 
certified EAT therapists. 
Main study parameters/endpoints: the main study parameter is the change on the Emotion 
Dysregulation Index  
Nature and extent of the burden and risks associated with participation, benefit and 
group relatedness: Participants receive regular therapy and participate in interviews/ 
questionnaires. The risks are negligible and the extra burden is minimal.  

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1. INTRODUCTION AND RATIONALE 
 
Autism spectrum disorder (ASD) is a severe neurodevelopmental disorder with a steadily 
rising world-wide prevalence of about 1-3% (Fombonne, 2018). Autism is marked by two 
phenomena. Firstly, patients with autism experience difficulties in the integration of 
information. This may result in difficulties in understanding others (theory of mind), a more 
detail-focused style of processing information (executive functioning), or difficulties in 
imagining future events. Secondly, patients with autism experience difficulties in processing 
sensory information, which may result in either overwhelming or decreased experiences of 
sensory input. As a consequence, daily life is highly stressful and traumatic with many 
unpredictable events that evoke emotion dysregulation (ED), a strong difficulty with 
regulating negative affect (Aldao, Nolen-Hoeksema, & Schweizer, 2010), resulting in low self-
esteem. Individuals with ASD rely on more maladaptive emotion regulation strategies 
(Samson, Wells, Phillips, Hardan, & Gross, 2015), which is associated with a wide range of 
negative outcomes, such as poorer social functioning (Nader-Grosbois & Mazzone, 2014) 
and more depression and anxiety symptoms(Mazefsky, Borue, Day, & Minshew, 2014; 
Swain, Scarpa, White, & Laugeson, 2015). Moreover, heightened levels of negative emotions 
may influence social functioning in ASD and vice versa. For example, a reduced ability for 
cognitive-reappraisal (i.e. the ability to change cognitions about a situation) is associated with 
higher levels of negative emotion, which in turn is related to more maladaptive behavior in 
ASD (Mazefsky, 2015). Vice versa, irritability may promote misinterpretation of social cues or 
inappropriate behavior in social interactions (Mazefsky, 2015). As such, ASD with severe 
levels of ED can be considered to have an ultra-high risk profile for developing other 
disorders, such as psychosis, anxiety, eating disorders, and depression. Treatment targeting 
this maladaptive cycle may improve outcomes for individuals with ASD. 
 
'Therapy-resistant' ASD  
In a part of the patients suffering from ASD, care as usual (psycho-education, medication, 
cognitive therapy, environmental adaptations) does not diminish ED at all. There are 
currently no guidelines or treatment options for this subgroup of severely impaired, therapy-
resistant individuals with ASD. The ‘dooming’ perspective of a lifelong disease may 
significantly damage patients and parents by creating a self-fulfilling prophecy and a cascade 
towards comorbid disorders, such as psychosis, depression, trauma, personality disorders, 
eating disorders and school dropout(Gillespie-Lynch, Kapp, Brooks, Pickens, & 
Schwartzman, 2017; Mogensen & Mason, 2015). 
 

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A promising novel treatment method targeting emotion dysregulation: equine-assisted 
therapy (eat)  
A highly promising method that may prove effective for therapy-resistant individuals with ASD 
is Equine-Assisted Therapy (EAT) (McDaniel Peters & Wood, 2017). While often met with 
prejudgment and skepticism, reports from parents and therapists suggest that EAT may have 
beneficial effects in youths with ASD. Horses have natural benefits over human therapists: 
they are experts in nonverbal communication, do not judge, offer unconditional acceptance, 
provide tactile comfort and give multiple real opportunities to gain experience with new 
behavior. EAT involves specific rehabilitative goals, individual tailored objectives and is 
directed by a healthcare professional (Fuller & Kaiser, 2020; Reichow, 2012; Trzmiel, 
Purandare, Michalak, Zasadzka, & Pawlaczyk, 2019). Patients can project and express their 
emotions and use the horse as a metaphor or a model. Just recently, a systematic review 
was published demonstrating highly potential effectiveness of EAT, especially with regard to 
both social functioning and emotion dysregulation (Trzmiel et al., 2019). However, this review 
also pointed towards the need for further high-quality research, as methodological 
shortcomings hampered prior studies (please see literature review). 
 
Adolescence: a (perhaps last?) 'Window of opportunity' to intervene  
In ASD literature, early childhood is considered to be the first ‘window of opportunity’ to 
intervene }(Fuller & Kaiser, 2020; Reichow, 2012). During this period, significant treatment-
related improvements in the core features of ASD have been reported (Peters-Scheffer, 
Didden, Korzilius, & Sturmey, 2011). We argue that a second (and perhaps last?) ‘window of 
opportunity’ for intervention is adolescence for two reasons: Firstly, like early childhood, 
adolescent age is related to major genetically preprogrammed neurological changes with a 
high sensitivity for environmental input across species (Malter Cohen, Tottenham, & Casey, 
2013; Mengler et al., 2014). In humans, myelination and synaptic pruning in the prefrontal 
cortex increases sharply, and neural connections between the prefrontal cortex and other 
regions of the brain are strengthened; this improves the efficiency of information processing, 
controlling impulses, planning ahead, enhanced decision-making, processing of emotional 
experiences and social information, and helps to more accurately evaluate rewards and risks 
(Burnett Heyes et al., 2015). Secondly, recently published longitudinal studies show that, 
particularly during adolescence, significant ASD symptom change may occur (Fein et al., 
2013; Sussman et al., 2015). Offering intervention during this time window may therefore be 
the last opportunity to improve adulthood outcomes.  
 
Aim of this research 

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For people with ASD, daily life is highly stressful and traumatic with many unpredictable 
events that evoke emotion dysregulation: a strong difficulty with appropriately regulating 
negative affect. Heightened levels of negative emotions may influence social dysfunctioning 
in ASD and vice versa. Treatment targeting this maladaptive cycle may improve outcomes 
for individuals with ASD. A part of the patients does not respond to care as usual. There 
currently are no guidelines or treatment options for this subgroup of severely impaired, 
therapy-resistant individuals with ASD. The ‘dooming’ perspective of a lifelong disease may 
significantly damage parents and patients by creating a self-fulfilling prophecy and a chronic 
cascade towards lifelong psychiatric disorders. Particularly problematic is that these patients 
often lack motivation for typically initiated forms of therapy, thereby further limiting their 
chances for a more favorable outcome. A highly promising method that may prove effective 
for therapy-resistant individuals with ASD is Equine-Assisted Therapy (EAT). While often met 
by prejudgment and skepticism, reports from parents and therapists as well as a recent 
systematic review (Trzmiel et al., 2019) suggest that EAT may have beneficial effects in 
youths with ASD. In addition to early childhood, a second (and perhaps last?) ‘window of 
opportunity’ for intervention is adolescence because of the major genetically pre-
programmed neurological changes occurring in this period, which heighten the sensitivity for 
environmental input.  
 
 
 

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2. OBJECTIVES 
 
Primary Objective:  
The primary objective is to significantly improve emotion dysregulation in a therapy-resistant 
group of youths with ASD (aged 11-18) after a 15-week treatment with Equine-Assisted 
Therapy (EAT). 
 
Secondary Objective(s):  
1. is to significantly improve emotion dysregulation in a therapy-resistant group of youths with 
ASD (aged 11-18) at the long term (1 year) after treatment with Equine-Assisted Therapy 
(EAT). 
 
2. is to significantly improve outcome measures of ASD, symptom severity, quality of life, 
self-esteem, global and family functioning and goal attainment as well as qualitative 
outcomes in (a) the short term (15 weeks) and (b) the long term (1 year). 
 
3. is to quantify the cost of EAT therapy when compared to a scenario including continued 
CAU. 
 
 

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3. STUDY DESIGN 
 
In order to be able to assess the effectiveness of the intervention, we designed a mixed-
methods strategy consisting of three elements: a randomized, multiple-baseline single-case 
design, a qualitative study and a cost-effectiveness study (see figure 1).  
 
The randomized, multiple-baseline single-case design  
Since heterogeneity is a major aspect of the population that could benefit from EAT, classic 
RCT models assuming homogeneity are less useful. In addition, an RCT comparing EAT 
with CAU would not be feasible if the treatment of choice (EAT) is withheld for a substantial 
amount of time from the group randomized to CAU. This group would either withdraw from 
participation immediately and/or seek EAT elsewhere, thereby directly undermining the 
validity of an RCT.  
 
Therefore, in line with the recommendations of ZonMw (Eindrapport 'Alternatieven voor RCT 
bij de evaluatie van effectiviteit van interventies!'), a randomized, multiple-baseline single-
case design will be carried out in 35 adolescents (11-18 years) with therapy-resistant ASD in 
n=4 therapy centers. Participants will complete repeated measurements during a baseline 
phase (phase A, 2-6 weeks), an intervention period (phase B, 15 weeks) and a post-
intervention period (phase C, 2-6 weeks). Phase A acts a control and will be compared with 
phase B. By applying multiple baselines of varying length, observed effects of the treatment 
can be distinguished from effects due to chance, thus increasing internal validity. The total 
duration of phases A and C is 8 weeks for each participant and, consequently, participants 
with a longer phase A will have a shorter phase C. Participants will be randomly assigned to 
a baseline duration by an independent researcher not involved in EAT nor the patient. During 
the total study period of 23 weeks, parents of the participants will complete an emotion 
regulation questionnaire (Emotion Dysregulation Inventory) three times a week to answer the 
primary outcome. Other assessments (ASD symptom severity, quality of life, self-esteem, 
global and family functioning and goal attainment) will take place at the baseline (T0), at the 
end of phase A (T1), after completion of phase B (T2), after the end of phase C (T3) and 
after one year (T4) (please see section outcomes).  
 
The qualitative study 
In the qualitative study, the aim is to obtain information from a varied group of adolescents, 
caregivers and professionals not only to gain insight into their individual experiences, but 
also into the effects of the intervention. Purposive sampling will identify those participants 

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who are most likely to provide rich information about their experiences. The study population 
consists of three groups:  
1. Adolescents referred to the intervention (n = 8-10)  
2. Caregivers of the adolescents referred to the intervention (n = 8-10)  
3. The professionals delivering the intervention (n = 4)  
 
We will use a maximum variation sampling approach of purposefully selecting a wide range 
of participants (Patton, 2015). The sample size is particularly dependent on the complexity of 
the research and the heterogeneity of the relevant characteristics. However, it is expected 
that 8-10 participants will be included in each group (adolescents and caregivers). The final 
number of subjects, however, will be determined on the basis of saturation. We will interview 
four members of the professionals group.  
 
 
The cost-effectiveness study  
We will use the 'Outcome generator' (https://effectencalculator.nl/) to answer questions on 
cost-evaluation and the effect of improved well-being. This instrument helps to make 
statements on innovative interventions based on dialogue. Using the 'Outcome generator' we 
will be able to analyze the social benefits of EAT and the costs saved by society due to 
positive results of EAT. Each year we will randomly select two cases from the participants to 
the EAT intervention. The evaluation sessions will take place approximately four months after 
the intervention is finished.  
  
 

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Figure 1. Design Pegasus study 

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4. STUDY POPULATION 
 
4.1 Population (base)  
Participants are adolescents between 11-18 years, with a diagnosis of autism spectrum 
disorder. Recruiting n=35 participants within four years is highly feasible, since recruitment is 
done both from within Karakter (where n=3200 patients with ASD are yearly treated) as from 
other sources (EAT centers, social media, patient organizations). 
 
4.2 Inclusion criteria 
In order to be eligible to participate in this study, a subject must meet all of the following 
criteria: 
 
between 11-18 years old;  
 
a clinical diagnosis of autism spectrum disorders according the DSM 5 as diagnosed 
by a BIG registered healthcare professional;  
 
insufficient emotion regulation after regular therapy for at least 1,5 years as indicated 
by a score above clinical cut-off (T-score = 65) on the EDI  
 
(T-score = 65) on the EDI;  
 
comorbidities are allowed  
 
4.3 Exclusion criteria 
A potential subject who meets any of the following criteria will be excluded from participation 
in this study: 
 
unable to respond to questions (parents or adolescents);  
 
no access to an Internet connection;  
 
insufficient mastery of Dutch language in parents or adolescents;  
 
physically incapable to work with the horses;  
 
Significant change in medication use;  
 
total IQ equal to or below 80 on the WISC-III-R, or WISC-V or WAIS-IV;  
 
allergic or phobic to horses;  
 
insufficient regulation to safely handle the horses;  
 
therapy with horses within the last two years.  
 
4.4 Sample size calculation 
The tool https://architecta.shinyapps.io/SingleCaseDesignsv02/ was used to calculate if the 
anticipated sample size had sufficient power. The following input was used:  
- 
the maximum number of participants is 30 

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- 
the effect size is 0.4 
- 
the number of measurements is 69 (three times a week for 23 weeks) 
- 
minimum number of baseline measurements is 2 (once a week; phase A) 
- 
minimum number of intervention measurements is 15 (once a week; phase B) 
- 
autocorrelation is 0.15  
- 
percentage outliers is 10% 
- 
percentage missing is 35% 
- 
the type 1 error rate (alpha) is 0.05 
In order to be able to do the power simulations, we specified the number of samples that 
have to be drawn (400 samples assignments), and the number sample simulations (100 
sample simulations). We found that with a sample size of 30, the estimated power is 0.94. To 
account for possible dropout, we added another five participants, thus including a total of 35 
participants. For the secondary outcomes we will correct for multiple testing by the False 
Discovery Rate (FDR)  
 
4.5 Study population for the Qualitative study 
Purposive sampling will identify those participants who are most likely to provide rich 
information about their experiences. The study population consists of three groups:  
1. Adolescents referred to the intervention (n = 8-10)  
2. Caregivers of the adolescents referred to the intervention (n = 8-10)  
3. The professionals delivering the intervention (n = 4)  
 
We will use a maximum variation sampling approach of purposefully selecting a wide range 
of participants (Patton, 2015). The sample size is particularly dependent on the complexity of 
the research and the heterogeneity of the relevant characteristics. However, it is expected 
that 8-10 participants will be included in each group (adolescents and caregivers). The final 
number of subjects, however, will be determined on the basis of saturation. We will interview 
four members of the professionals group.  
 
4.6 Study population for the cost effectiveness study 
Each year we will randomly select two cases from the participants to the EAT intervention. 
The evaluation sessions will take place approximately four months after the intervention is 
finished.  
 

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5. TREATMENT OF SUBJECTS 
 
5.1 Investigational product/treatment 
During the first session(s) of EAT, the personal goals of the adolescent are determined. The 
goals of the adolescent may differ from the goals of caregivers. This is an essential part of 
the therapy, as most of the adolescents have been sent to therapies with goals set by adults. 
The therapist can help the patient to set personal goals by means of observations made and 
by asking if the patient recognizes what happens during the session with respect to real-life. 
People act in the same way in most situations, so if the patient does not immediately 
recognize the pattern, the behavior will soon be repeated and the therapist can help the 
patient recognize the pattern. Examples of personal goals verbalized by adolescents are: 
“How can I get friends and keep them?”, “I want to go to school”, “I want to join the army, so I 
have to be able to control my anger”, ”How can I deal with a traumatic event?”.  
 
After this, the therapist determines the smaller steps that are needed to reach the goal. For 
example, in case of the goal "How can I get friends and keep them?", the first step is to 
observe other living beings (in this case horses interacting with each other). Observations 
can be made from a safe distance and the patient learns to be aware of the nonverbal 
signals given by the horses. The transfer to real life is facilitated by a homework assignment 
to observe nonverbal behavior of other people and successful when the adolescents 
spontaneously starts to observe the nonverbal signals people make. The second step in 
making friends is to make contact, a skill that can be practiced over and over with the horses. 
The horses, being a prey and a herd animal, will give immediate and neutral feedback as 
they are used to carefully observing the surroundings and reacting to each other. The herd is 
extremely important for their safety and horses observe every change of their fellow horses 
and, in this case, the patient. Changes can be in muscle tension, breathing, facial 
expression, posture, etc. Patients can experiment with different behaviors and see, hear and 
feel the reactions that are evoked in the horse. If the behavior of the adolescent is calm and 
straightforward, the horse will respond calmly and acceptingly. A third step in making friends 
is joined interaction with the horse, for instance walking with the horse, grooming the horse, 
putting the horse on a sail or leading the horse over an obstacle. All these exercises can be 
made more complex by not using a leading rope. The patient can experiment with different 
postures, use of voice, energy, velocity, control of movements and handling all kinds of 
emotions such as fear, frustration, anger or sadness, but also with pride, tenderness and joy. 
After each activity with the horse, the therapist shares his/her observations with the patient. 
As a result, the patient becomes aware of his behavior and gets the opportunity to 
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at home and at school: for example, to observe other people or to adjust his behavior in the 
same way he did with the horses and tell the next session what happened. We use an 
experience leaflet including the treatment goals, the experiences of the sessions and the 
homework to enhance the transfer to real life. Concrete questions are often needed to 
describe the session (What happened? What did you learn?). If a form of additional support 
is needed, we can tell the parent(s) about the homework or send a picture of the patient with 
the horse, etc. In case of interaction problems between the patient and the parents, which 
nearly always exist inherent to the core of the disorder, parents can be invited to join the 
therapy. We have special exercises that can be performed with more people, such as leading 
the horse together through a special obstacle course, grooming the horse while holding each 
other without talking or switching roles. Usually, two sessions with parents are scheduled.  
 
EAT sessions will be held once a week for 15 weeks. Each session will last 60 minutes using 
a standardized protocol (ORS, discuss the homework, exercise, feedback, repeat the 
exercise, new homework, SRS). A session starts with assessing the well-being of the patient 
at home, at school and in total over the last week by the ORS (Outcome Rating Scale) (5 
minutes). The therapist asks what the patient remembers from the last session and how the 
exercises at home worked out. Then a new exercise is started conform the protocol, if 
necessary adjusted to the goal of the patient and the possibilities of the patient and the 
horse. After the session, the patient completes the SRS (Session Rating Scale) 
questionnaire to promote awareness of the attainment of his goals, to learn to express 
himself in an acceptable way and to give feedback of the session and the therapist. 
Subsequently, an appointment is made about the homework to enhance the transfer to real 
life.  
 
All therapists are BIG/SKJ registered healthcare professionals and qualified to work with 
horses. Every six months, a consensus meeting will be organized with all EAT-therapists to 
maintain treatment fidelity. Videos of EAT sessions performed by the therapists will be used 
for this purpose.  
 
EAT does not seem to have a negative effect on the well-being of the horses, as indicated by 
unchanged plasma cortisol levels and heart rate variability (Malinowski et al., 2018). 
 
Subject can use medication as usual. As former therapy was ineffective, no other therapy will 
be given. 
 
 

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6. INVESTIGATIONAL PRODUCT  
 
     N/A 
 
 

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7. NON-INVESTIGATIONAL PRODUCT 
 
     N/A 
 
 

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8. METHODS 
8.1 Study parameters/endpoints 
8.1.1 Main study parameter/endpoint 
The primary objective is to significantly improve emotion dysregulation in a therapy-resistant 
group of youths with ASD (aged 11-18) after a 15-week treatment with Equine-Assisted 
Therapy (EAT). 
 
8.1.2 Secondary study parameters/endpoints (if applicable) 
Secondary study parameter is to assess emotion dysregulation in a therapy-resistant group 
of youths with ASD (aged 11-18) at the long term (1 year) after treatment with Equine-
Assisted Therapy (EAT). 
 
Secondary study parameters are to assess the following outcome measures of ASD, 
symptom severity, quality of life, self-esteem, global and family functioning and goal 
attainment as well as qualitative outcomes in (a) the short term (15 weeks) and (b) the long 
term (1 year). Another measure is to quantify the cost of EAT therapy when compared to a 
scenario including continued CAU. 
 
8.2 Randomisation, blinding and treatment allocation 
Participants will be randomly assigned to one of the five pre-defined baseline lengths to 
increase the internal validity of the design with a 1:1 allocation using permuted blocks of 
random sizes. The block sizes will not be disclosed to ensure concealment. Participants will 
be randomized using www.randomization.com, an online randomization tool. Allocation 
concealment will be ensured, as the person performing the randomization has no other role 
in the study. This person will prepare the randomization lists and seal the envelopes. The 
randomization code will not be released until the patient has been recruited for the trial, 
which will take place after completion of all baseline measurements. To ensure concealment 
of allocation, the steps involved in randomization, outcome measurements and treatment are 
separate. All patients who give consent for participation and who comply with the inclusion 
criteria will be randomized. Randomization will be requested by the research assistant in 
charge of recruitment and outcome measurement.  
 
8.3 Study procedures for the randomized, multiple-baseline single-case design  
EAT sessions will be held once a week for 15 weeks and are like regular standard EAT 
sessions. Each session will last 60 minutes using a standardized protocol (ORS, discuss the 
homework, exercise, feedback, repeat the exercise, new homework, SRS). A session starts 
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by the ORS (Outcome Rating Scale) (5 minutes). The therapist asks what the patient 
remembers from the last session and how the exercises at home worked out. Then a new 
exercise is started conform the protocol, if necessary adjusted to the goal of the patient and 
the possibilities of the patient and the horse. After the session, the patient completes the 
SRS (Session Rating Scale) questionnaire to promote awareness of the attainment of his 
goals, to learn to express himself in an acceptable way and to give feedback of the session 
and the therapist. Subsequently, an appointment is made about the homework to enhance 
the transfer to real life.  
 
Above this, during the total study period of 23 weeks, parents of the participants will 
complete an emotion regulation questionnaire (Emotion Dysregulation Inventory) three times 
a week to answer the primary outcome. Other assessments (ASD symptom severity, quality 
of life, self-esteem, global and family functioning and goal attainment) will take place at the 
baseline (T0), at the end of phase A (T1), after completion of phase B (T2), after the end of 
phase C (T3) and after one year (T4) (please see section outcomes).  
 
At admission to one of the participating centers a psychiatric evaluation will be made 
resulting in a diagnosis according to Diagnostic and Statistical Manual of Mental Disorders, 
Fifth Edition (DSM-5). Clinical DSM-5 diagnoses are established by a multidisciplinary team 
based on information (developmental history, child observation and psychiatric assessment 
and review of clinical and prior records, including information available from school or other 
professional institutions involved with the child), gathered by a child psychiatrist and a child 
psychologist, resulting in a diagnosis. Emotion Dysregulation (primary measure)  
 
Data collection  
Emotion Dysregulation Inventory (EDI)  
Emotion Dysregulation Inventory (EDI) (Mazefsky, Yu, & Pilkonis, 2020; Mazefsky, Yu, 
White, Siegel, & Pilkonis, 2018) is specifically designed to measure emotion regulation 
impairments in youths and adolescents with ASD. The EDI-short form is a validated, change-
sensitive, 13-item caregiver report measure of emotion regulation impairment for individuals 
who are at least 6 years of age. The EDI was developed using the item response theory 
(IRT) analysis and none of the final items had evidence of differential item functioning (e.g., 
psychometric biases) by gender, age, intellectual ability and verbal ability, making it suitable 
for use across heterogeneous populations. Items on the EDI measure how problematic 
behaviours have been during the past day. The scale used is Not at all=0, Mild=1, 
Moderate=2, Severe=3, or Very Severe=4. The EDI short form includes two scales: a 7-item 
Reactivity Index and a 6-item Dysphoria Index. Index raw scores can be converted into t-

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scores or theta scores based on a sample of 1755 individuals with ASD (Mazefsky et al., 
2018) or based on a sample of 1000 youths matching the US census as general population 
norms (Mazefsky et al., 2020). For the purposes of this study we will administer the 13-item 
EDI short form three times a week (for 23 weeks).  
 
Quality of life  
Kidscreen-27 (parents) and Kidscreen-27 (adolescents). The KIDSCREEN-27 
(https://www.kidscreen.org/english/questionnaires/kidscreen-27-short-version/) is a generic 
health-related quality of life (HRQOL) questionnaire for children and adolescents applicable 
to healthy and chronically ill children and adolescents aged between 8 and 18 years. There 
are two versions of the questionnaire: a self-complete version (child/ adolescent) and a proxy 
version (parent/proxy). The KIDSCREEN-27 consists of 27 items measuring five dimensions: 
physical well-being, psychological well-being, parent relations & autonomy, social support & 
peers and school environment. Items are answered on a five-point Likert-type scale 
assessing frequency (never (1), seldom (2), sometimes (3), often (4), and always (5)) or 
intensity (not at all (1), slightly (2), moderately (3), very (4), and extremely (5)) with a one-
week recall period. Scores are coded from 1 to 5, negatively formulated items are recoded 
and the sum scores for respective dimensions are converted into T scores with a mean of 50 
and a standard deviation (SD) of 10. Higher scores indicate better HRQOL. The 
KIDSCREEN-27 has been shown to have robust psychometric properties. The internal 
consistency of the domains was between 0.81 and 0.84, and the test-retest reliability of the 
domains ranged from 0.61 to 0.74. The KIDSCREEN-27 (parents and adolescents) will be 
assessed at baseline (T0), at the end of phase A (T1), after completion of phase B (T2), after 
the end of phase C (T3) and after one year (T4).  
 
Psychometric Evaluation  
Global functioning (CBCL/6-18, YRS/11-18, TRF/6-18) For assessing emotional and/or 
behavioural problems we will use the CBCL/6-18 (https://aseba.org/), completed by parents 
or substitutes, the TRF/6-18, completed by teachers and other school staff, and the YSR/11-
18, completed by youths. All three questionnaires include more than 100 items assessing 
behavioural and emotional problems that are answered on a three-point Likert-type scale (0 
= not true, 1 = somewhat or sometimes true, 2 = very true or often true) by parents. The 
scores will display eight problem scales (withdrawn (1); somatic (2); anxious (3); social (4); 
thought (5); attention (6); rule-breaking (7); aggressive (8)) and other problems. The sum of 
the problem scales 1, 2 and 3 form the ‘internalizing behaviour’ scale, whereas 7 and 8 form 
‘externalizing behaviour’. All subscales together count for the total problem scale. Some 
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higher scores on the syndrome scales indicate a greater severity of problems. A T-score of 
63 (90th percentile) demarcates the clinical range, which is an indication that a child needs 
professional help. For the competence scales, lower scores indicate greater severity. A T-
score < 37 indicates the clinical range. The CBCL/ 6–18 has well-established psychometric 
properties in clinical, non-clinical, and cross-cultural populations. The CBCL 6-18 (parents), 
YSR (adolescents), TRF (teacher) will be assessed at baseline (T0).  
 
Global functioning (BPM-P, BPM-Y, BPM-T) The Brief Problem Monitor (BPM) 
(https://aseba.org/) is a rating instrument for monitoring children’s functioning and responses 
to interventions and is a short version of the CBCL/YSR/TRF. The BPM consist of a 
minimum set of items to be completed in 1 to 2 minutes by parents (BPM-P), teachers (BPM-
T) and youths (BPM-Y). Nineteen items of the CBCL/6–18 (or TRF or YSR) make up the 
BPM: 6 items for attention (all 6 from the CBCL/6–18 attention problems scale), 7 items for 
externalizing (all 7 from the CBCL/6–18 aggression scale), and 6 items for internalizing (5 
from the CBCL/6–18 anxiety/depression and 1 from the CBCL/6–18 withdrawn/depressed 
scales). Each item is rated 0 = not true, 1 = somewhat true, or 2 = very true. Parallel items 
and scales on the BPM & the CBCL/6-18, TRF and YSR enable us to link comprehensive 
initial and outcome assessments to BPM scores. The BPM-P, BPM-Y will be assessed at the 
end of phase A (T1), after completion of phase B (T2), after the end of phase C (T3) and 
after one year (T4). The BPM-T (teachers) will be assessed after the end of phase C (T3).  
 
Communication and social functioning (SRS-2)  
The Social Responsiveness Scale – Second edition (SRS-2) (Constantino et al., 2003) 
measures deficits in social behaviour associated with ASD and can be used to assess the 
severity of symptoms in ASD (Frazier et al., 2012). The questionnaire will be completed by 
multiple raters (parents and teachers). The SRS-2 consists of 65 items scored in a Likert-like 
scale format ranging from not true=1, sometimes true=2, often true=3 to almost always true 
=4. It is designed to identify social impairment intrinsic to ASD and to quantify its severity 
across the duration of the treatment. A total score and five treatment subscale scores (Social 
Awareness; Social Cognition; Social Communication; Social Motivation; and Restricted 
Interests and Repetitive Behaviour) are obtained. The accepted diagnostic criteria (cut point) 
for the SRS-2 for the association with a diagnosis of ASD are: <=59 (normal); 60–75 (mild to 
moderate ASD); and =>76 (severe ASD). The SRS-2 (parents) will be assessed at baseline 
(T0), at the end of phase A (T1), after completion of phase B (T2), after the end of phase C 
(T3) and after one year (T4). The SRS-2 (teachers) will be assessed at the baseline (T0) and 
after the end of phase C (T3).  
 

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Rosenbergh self-esteem (RSES)  
The Rosenberg Self-Esteem Scale (RSES) (Rosenberg, 1979) will be used to assess self-
esteem. It is a widely used 10-item Likert-scale self-esteem measure. Items are answered on 
a four-point scale — ranging from strongly agree to strongly disagree — measuring positive 
and negative feelings towards the self. The Dutch version of the RSES is found to be a one-
dimensional scale with high internal consistency and congruent validity and a Cronbach’s 
alpha of 0.89 (Franck, De Raedt, Barbez, & Rosseel, 2008). Rosenberg Self-Esteem Scale 
will be assessed at the baseline (T0), at the end of phase A (T1), after completion of phase B 
(T2), after the end of phase C (T3) and after one year (T4).  
 
Family functioning, prior beliefs, satisfaction  
Family functioning  
Family functioning is assessed using a validated questionnaire: the Family Functioning 
Questionnaire (VGFO, 34 items) (https://www.praktikon.nl/wat-we-doen/vragenlijsten/vgo). 
The Family Functioning Questionnaire can be answered on a four-point scale ranging from 1 
(not applicable) to 4 (completely applicable) with lower scores indicating more problems in 
family functioning. This questionnaire will be assessed at the baseline (T0) and after the end 
of phase C (T3).  
 
Prior beliefs and motivation for therapy, satisfaction  
Parents and adolescents prior beliefs about the short-term and long-term success and 
burden of the intervention are evaluated using a 6-item questionnaire in which parents and 
adolescents rate their prior believes on a 10-point scale ranging from 1 (completely disagree) 
to 10 (completely agree). This measurement will also be used to examine if randomization is 
successful by verifying if the five groups do not differ in believes about the effectiveness of 
the intervention at the baseline. Prior beliefs of parents and adolescents will be assessed at 
the baseline (T0). Parents and adolescents can rate their overall treatment trajectory on a 
scale of 0 to 10. Satisfaction will be measured after the end of phase C (T3).  
 
Goal attainment and adherence  
SRS/ORS  
For collecting client feedback we will use two brief questionnaires, the Outcome Rating Scale 
(ORS) and Session Rating Scale (SRS), which will be easily administered on a regular basis 
during treatment (https://www.scottdmiller.com/ scholarly-publications-hand-outs-vitae/).This 
allows treatment sessions to be evaluated at any time to ascertain whether or not individual 
treatments are ‘on the right track’ towards a successful outcome. The ORS is primarily 
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session. The SRS is administered at the end of the session and deals with how the client has 
experienced the treatment session. The outcomes of the questionnaires are reflected in a 
graph on an iPad (or on paper when an iPad is not available) per interview to allow the height 
of the score and progress to be visualized during the sessions. The ORS and SRS both have 
a high internal consistency and an average correlation with other outcome measurements. 
The therapist will assess the SRS/ORS each session.  
 
Goal Attainment Scale  
Goal Attainment Scale (Kiresuk & Sherman, 1968) is a method of scoring the extent to which 
the patient’s individual goals are achieved in the course of the intervention. In effect, each 
patient has his own outcome measure, but this is scored in a standardized way as to allow 
statistical analysis. Each goal is rated on a six-point scale, capturing the degree of attainment 
for each goal area: Patient starts on -2. When he achieves somewhat better this is scored -1. 
When the patient achieves the expected level, this is scored 0. When he achieves a better 
than expected outcome this is scored +1 (somewhat better) or +2 (much better). Achieving a 
worse than expected outcome is scored -3. In this study, a maximum of 3-4 goals are 
identified, which are incorporated into a single GAS score. The GAS will be assessed in the 
fifth, tenth en fifteenth sessions.  
 
8.4 Study procedures for the qualitative study  
The first contact of adolescents and caregivers will be done by the professional involved in 
the intervention. Then the qualitative researcher will be introduced by the professional. 
Caregivers will receive a formal letter explaining the qualitative part of the study and an 
informed consent form. The qualitative researcher will only contact those who have given 
their written informed consent to schedule an interview. All interviews will be assessed by the 
qualitative researcher together with an experienced expert parent or a young experienced 
expert with autism (depending on the subgroup). Interviews will last for 45–60 minutes. 
Caregivers and adolescents will be interviewed separately. Each participant will be 
interviewed twice (before the start of the intervention and 30 weeks after the intervention).  
 
The professionals will be interviewed at their workplace at a convenient time for them. All 
interviews will be assessed by a qualitative researcher and an experienced mental health 
professional. Interviews will last for 45–60 min. Each professional will be interviewed twice 
(at the start of the project and when all participants are included).  
 
Data collection  

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A total of n=8-10 adolescents and their caregivers will be invited to participate in individual 
semi-structured in-depth interviews of one hour. The interview will consist of open questions 
in order to obtain a complete as possible picture of the participants' experiences (Kvale & 
Brinkmann, 2009). We work with an iterative topic list. The topic list will be exploratory in 
nature and focus on gathering knowledge and experiences about the topic. Possible 
examples of questions for the adolescents and their parents include: What are your 
expectations of the intervention? What should be maintained or strengthened in the 
intervention? What are facilitators, barriers? What benefits have you derived from the 
intervention? How did you experience the intervention? What was your experience with the 
therapist?, etc.  
 
The EAT therapists will be interviewed to describe and evaluate therapeutic elements and 
implementation processes. Possible examples of questions are: What characterizes the 
referral procedure for the intervention? What are the barriers and facilitators for referral to the 
intervention? How do participants perceive the intervention offered? What aspects are 
missing from your perspective? How is the intervention implementation experienced by EAT 
therapists?, etc.  
 
8.5 Study procedures for the cost-effectiveness study  
We will organize three evaluation sessions. In each session a participant of the main study 
will be invited. All sessions will have a trained panel chairman. Furthermore, five to eight 
persons are invited to participate. The persons are all affected by or have contributed to the 
intervention and add to a variety of perspectives (for example, parents, teacher, professional, 
social worker, etc.). Depending on the ability, the adolescent may attend the session. The 
conversations will take 3 hours at most, including several breaks.  
 
Data collection  
Two questions are central to this conversation: "What has changed in the lives of the 
participants after the EAT intervention?" and "What would (hypothetical) have happened if 
the EAT intervention was not conducted in terms of well-being, lifetime costs and care 
expenses?"  
 
In the first part of the conversation - the reconstruction - those present will make a 
reconstruction of the period from admission to the intervention. The moderator will make sure 
that there will be a complete overview of the events, which will be composed as much as 
possible prior to the meeting based on available data in the patient clinical files. During the 
conversation, information will be structured according to experiences and events (What 

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happened in the child’s life? How did the child experience the interventions over time?) and 
actions (Which interventions and actions have been used?). In the second part of the 
conversation the (added) value of the intervention for the participant will be discussed. To do 
so, a reference situation will be drawn (Where would the participant have ended up without 
the intervention? or Which (care) facilities did the participant previously make use of and 
What facilities were addressed in this period without the intervention?).  
 
At the end of the meeting, five of the more reflective questions will be presented to those 
involved.  
1. Please rate: How do you rate the intervention?  
2. Social contacts: What has the intervention contributed to your social life?  
3. Thresholds: What made it difficult to participate in the intervention?  
4. Cooperation: How did the people of the intervention work together with other parties? 
5. Points for improvement: If you could improve the intervention, what would you suggest?  
 
8.6 Withdrawal of individual subjects 
Subjects can leave the study at any time for any reason if they wish to do so without any 
consequences. The investigator can decide to withdraw a subject from the study for urgent 
medical reasons. 
 
8.6.1 Specific criteria for withdrawal (if applicable) 
 
          n/a 
 
8.7 Replacement of individual subjects after withdrawal 
Individual subjects are replaced if they leave the study till 35 participants have participated in 
more than 10 sessions. We will investigate the reason why participants leave the study so we 
can adjust the EAT or the measurements, if possible without methodological consequences.  
 
8.8 Follow-up of subjects withdrawn from treatment 
Regular therapy will be continued after subjects have left the study 
 
8.9 Premature termination of the study 
The study will only be terminated when the research team, therapists and the patient panel 
team agree to stop.       
 
 

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9. SAFETY REPORTING 
9.1 Temporary halt for reasons of subject safety 
In accordance to section 10, subsection 4, of the WMO, the sponsor will suspend the study if 
there is sufficient ground that continuation of the study will jeopardise subject health or 
safety.  The sponsor will notify the accredited METC without undue delay of a temporary halt 
including the reason for such an action. The study will be suspended pending a further 
positive decision by the accredited METC. The investigator will take care that all subjects are 
kept informed.  
 
9.2 AEs, SAEs and SUSARs 
9.2.1 Adverse events (AEs) 
Adverse events are defined as any undesirable experience occurring to a subject during the 
study, whether or not considered related to the experimental intervention. All adverse events 
reported spontaneously by the subject or observed by the investigator or his staff will be 
recorded. 
 
9.2.2 Serious adverse events (SAEs) 
A serious adverse event is any untoward medical occurrence or effect that  
 
results in death; 
 
is life threatening (at the time of the event); 
 
requires hospitalisation or prolongation of existing inpatients’ hospitalisation; 
 
results in persistent or significant disability or incapacity; 
 
is a congenital anomaly or birth defect; or 
 
any other important medical event that did not result in any of the outcomes listed 
above due to medical or surgical intervention but could have been based upon 
appropriate judgement by the investigator. 
An elective hospital admission will not be considered as a serious adverse event. 
 
The investigator will report all SAEs to the sponsor without undue delay after obtaining 
knowledge of the events. 
 
The sponsor will report the SAEs through the web portal ToetsingOnline to the accredited 
METC that approved the protocol, within 7 days of first knowledge for SAEs that result in 
death or are life threatening followed by a period of maximum of 8 days to complete the initial 
preliminary report. All other SAEs will be reported within a period of maximum 15 days after 
the sponsor has first knowledge of the serious adverse events. 
 

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9.2.3 Suspected unexpected serious adverse reactions (SUSARs) 
n/a 
 
9.3 Annual safety report 
n/a 
 
9.4 Follow-up of adverse events 
All AEs will be followed until they have abated, or until a stable situation has been reached. 
Depending on the event, follow up may require additional tests or medical procedures as 
indicated, and/or referral to the general physician or a medical specialist. 
SAEs need to be reported till end of study within the Netherlands, as defined in the protocol  
 
 
 

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10. STATISTICAL ANALYSIS 
 
10.1 Study parameter(s) for the randomized, multiple-baseline single-case design  
Data will be analysed using SPSS V.24.0 for Windows (SPSS Incorporated), specific 
software for single-case experimental designs available on  
https://architecta.shinyapps.io/SingleCaseDesignsv02/ and the statistical software R 
(Comprehensive R Archive Network; https://cran.r-project.org/) for the hierarchical linear 
modelling. Descriptive statistics will be performed for baseline characteristics of the study 
population. Parametric data will be presented as means with SD, and non-parametric 
distributed variables as median with IQRs. For the primary outcome we will combine visual 
analyses, randomization tests and effect sizes for a comprehensive analysis of intervention 
based on the state-of-the-art knowledge on analysing a randomized multiple-baseline single-
case design (Heyvaert et al., 2017).  
 
Time series analyses  
Firstly, data will be visually inspected within and between phases with respect to 1) level 2) 
trend 3) variability 4) immediacy of the effect 5) overlap and 6) consistency of data across 
similar phases (Bulté & Onghena, 2012; Kratochwill et al., 2010). Secondly, the intervention 
effect will be statistically tested by applying a sequential approach. We will test the null 
hypothesis of no treatment effect for any of the cases with the non-parametric approach to 
combine randomization test p values (Manly, 2007). If it is determined that the intervention 
has indeed a statistically significant effect on emotion regulation, we will use the hierarchical 
linear modelling (Van Den Noortgate & Onghena, 2003) approach for analysing the data in 
closer detail and to obtain the parameter estimate of and to further model the average 
treatment effect and individual treatment effects. This average treatment effect is an effect 
size and will as such be compared with the meta-analytic effect size as obtained in other 
studies. There will be no statistical testing in this final step. The interaction between 
treatment effect and time will be included in the hierarchical linear model in order to model 
differential trends.  
 
Single time points analyses  
Pre-treatment scores on the EDI will be compared to post-treatment and follow-up scores on 
the EDI and other secondary measurements using a non-parametric Wilcoxon signed rank 
test. An effect size will be obtained from this analysis, with the follow-up versus pre-treatment 
comparison as input for this effect size.  
 
10.2 Study parameter(s) for the qualitative study 
The interviewer will audiotape the interview with the participant's permission. Immediately 
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Furthermore, a reflexive journal will record the overall process of data collection. The data 
collection and analysis will occur concurrently. After each interview, the researcher will 
transcribe the recording verbatim and then code the transcript to reveal broad or initial 
categories or themes. Interview transcripts and observation narratives will be coded 
thematically by two researchers independently.  
 
Atlas-ti will be used for coding, management and retrieval of data. Throughout the analysis, 
researchers will use memos and reflective diaries to engage with the data and refine 
emergent themes through an iterative and inductive process. Data triangulation will be 
achieved by comparing interview data from adolescents and caregivers to explore the 
intervention from different perspectives. 
 
10.3 Study parameter(s) for the cost-effectiveness study 
We will use the 'Outcome generator' (https://effectencalculator.nl/) in the cost-effectiveness 
study to answer questions on cost evaluation and the effect of improved well-being. This 
instrument helps to make statements on innovative interventions based on dialogue. Using 
the 'Outcome generator' we will be able to analyze the social benefits of EAT and the costs 
saved by society due to positive results of EAT.  
 
The outcomes are placed on a timeline and described in terms of social benefits (such as: 
went back to school, less reactivity and improved emotion regulation, less violent/getting 
angry, etc.) and saved costs (less admission to institutions, less therapy, future perspective 
on work, etc.), including a corresponding price tag. The result is a visual overview of the 
social benefits and cost savings offered by the intervention.  
 
10.4 Mixed methods 
We will use an embedded mixed-methods methodology to triangulate both qualitative, 
quantitative methodologies and the cost-effectiveness in this study (Creswell & Plano Clark, 
2011). Qualitative interviews will be embedded in the randomized, multiple-baseline single-
case design to evaluate the effectiveness of the EAT intervention. Data will be collected 
concurrently during the project. Using a mixed-methods design we enable us to combine the 
results of the three components and explain agreements and disagreements between the 
findings. Furthermore, the use of qualitative data will provide complementary data about the 
nature, acceptability, perceived usefulness, barriers and issues of the EAT intervention. It will 
enable us to draw more meaningful conclusions about the EAT intervention.  
 
 

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11. ETHICAL CONSIDERATIONS 
 
11.1 Regulation statement 
The current study is conducted according to the principles of the “Declaration of Helsinki”, 
adopted by the 18th WMA General Assembly, Helsinki, Finland, June 1964 and amended by 
the 64th WMA General Assembly, Fortaleza, Brazil, October 2013, in accordance with the 
Medical Research Involving Human Subjects Act (WMO) and in accordance to the 
Guidelines for Good Clinical Practice (GCP) (CPMP/ICH/135/95 – 17th of July 1996).  
The protocol of the current study will be submitted to the local “Commissie Mensgebonden 
Onderzoek” (CMO) Arnhem-Nijmegen, an official METC in The Netherlands. Possible 
participants and their parents will not be approached before formal approval has been 
granted.  
 
11.2 Recruitment and consent 
We will recruit therapy-resistant and therapy-avoiding youths with ASD who are motivated to 
undergo Equine-Assisted Therapy (EAT) through screening by the therapists in the 
participating centers. Further inclusions and exclusions will be assessed using a checklist 
during an intake interview by a research assistant. Patients and their caregivers are informed 
about the intervention, the aims of the study and the measurements. They receive this 
information both orally and in print. After one week, participants aged 12 to 17 and their 
parents will be asked to sign a written informed consent, children aged 11 will be asked to 
sign a child version. 
 
11.3 Objection by minors or incapacitated subjects  
The code of conduct relating to expressions of objection by minors participating in medical 
research is applicable in the current study (https://english.ccmo.nl/binaries/ccmo-
en/documents/publications/2002/01/01/code-of-conduct-relating-to-expressions-of-objection-
by-minors-participating-in-medical-
research/Code+of+conduct+relating+to+expressions+of+objection+by+minors+participating+
in+medical+research.pdf). 
 
11.4 Benefits and risks assessment, group relatedness 
The potential value of this study is that this study will create an opportunity for therapy 
resistant adolescents to profit from EAT, especially with regard to both social functioning and 
emotion dysregulation.  
 

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Given that the intake procedure and the treatment sessions are part of care as usual, only 
the filling out of the questionnaires, and for some joining an interview, are extra. Since 
routine outcome monitoring is part of care as usual as well, the extra burden is relatively 
small. Based on a pilot study in n=6 adolescents and their parents (May/June 2020), the 
average time to complete the T0 questionnaires was 15 minutes for adolescents (Kidscreen-
27, YSR 11-18, Rosenberg self-esteem and prior beliefs) and 25 minutes for parents 
(Kidscreen-27, CBCL 6-18, VGFO, EDI, SRS-2 and prior beliefs). Furthermore, we asked 
caregivers to complete the EDI three times a week for three weeks. None of the parents in 
the pilot felt completing these questions as a burden.  
 
11.5 Compensation for injury 
The investigator has a liability insurance which is in accordance with article 7 of the WMO.  
 
The sponsor (also) has an insurance which is in accordance with the legal requirements in 
the Netherlands (Article 7 WMO). This insurance provides cover for damage to research 
subjects through injury or death caused by the study. The insurance applies to the damage 
that becomes apparent during the study. 
 
11.6 Incentives  
Compensation for extra traveling costs to the horse center will be given to a max of 50 euro. 
The EAT will be paid by  municipality or the research team. 
 

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12. ADMINISTRATIVE ASPECTS, MONITORING AND PUBLICATION 
 
12.1 Handling and storage of data and documents 
The data of the current study are handled with confidentiality. The handling of personal data 
of subjects is in accordance with the European General Data Protection Regulation (in 
Dutch: Algemene Verordening Gegevensbescherming, AVG). In accordance with the AVG, 
the data protection officer (dpo@karakter.com) has been appointed. The research team is 
responsible for the processing of the data.  
 
After a participant is included in the study, a code number (i.e. 101,102,...135) is assigned by 
one of the investigators. The code list will be digitally stored on the H-drive of Karakter, is 
password protected and only accessible to the investigators that are involved in the project. 
The location of the code list is different from the location of the data. Data is stored on a 
secure CASTOR EDC server at Radboud University Medical Centre, which is located on two 
separate sites and a back-up is made on a daily basis. CASTOR EDC is in accordance with 
the guidelines for valid data storage systems of the GCP 
(http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=11).  
 
Paper documents, such as the consent forms, will be stored separately and secured for 10 
years. The investigator will retain originals of all source documents for a period of 5 years. In 
accordance with the GCP guidelines, all study-related documents are archived for at least 15 
years.  
 
When required for urgent medical reasons, responsible medical professionals will receive 
access to the personal source data. When this is needed, subject and their parents/legal 
caregivers are informed.  
 
After completion of the study and study reporting, data will be transferred to the Dutch 
National Data Archive (DANS). From DANS data are accessible for all researchers in the 
Netherlands. Researchers from outside the Netherlands can have access to the data 
according to the guidelines from DANS 
 
12.2 Monitoring and Quality Assurance  
n/a 
 

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12.3 Amendments  
Amendments are changes made to the research after a favourable opinionapproval by the 
accredited METC has been given. All amendments will be notified to the METC that gave a 
favourable opinionapproval.  
 
Non-substantial amendments will not be notified to the accredited METC and the competent 
authority, but will be recorded and filed by the sponsor.  
 
12.4 Annual progress report 
The sponsor/investigator will submit a summary of the progress of the trial to the accredited 
METC once a year. Information will be provided on the date of inclusion of the first subject, 
numbers of subjects included and numbers of subjects that have completed the trial, serious 
adverse events/ serious adverse reactions, other problems, and amendments.  
 
12.5 Temporary halt and (prematurely) end of study report 
The investigator/sponsor will notify the accredited METC of the end of the study within a 
period of 8 weeks. The end of the study is defined as the last patient’s last measurement.  
 
The sponsor will notify the METC immediately of a temporary halt of the study, including the 
reason of such an action.  
 
In case the study is ended prematurely, the sponsor will notify the accredited METC within 15 
days, including the reasons for the premature termination. 
 
Within one year after the end of the study, the investigator/sponsor will submit a final study 
report with the results of the study, including any publications/abstracts of the study, to the 
accredited METC.  
 
12.6 Public disclosure and publication policy 
Prospective trial registration will be done in the Netherlands Trial Register (NTR). The results 
of the study will be submitted to a peer-reviewed journal and presented at both national and 
international conferences. Disclosure of results will be conducted according to the CCMO 
statement on publication policy. This indicates that both positive and negative results will be 
published. 
 
After completion of the study, data will be transferred to the Dutch National Data Archive 
(DANS). From DANS data are accessible for all researchers in the Netherlands. Researchers 

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from outside the Netherlands can have access to the data according to the guidelines from 
DANS.  

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13. STRUCTURED RISK ANALYSIS  
n/a 
 
 
 
 

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14. REFERENCES 
 
Aldao, A., Nolen-Hoeksema, S., & Schweizer, S. (2010). Emotion-regulation strategies 
across psychopathology: A meta-analytic review. Clin Psychol Rev, 30(2), 217-237. 
doi: 10.1016/j.cpr.2009.11.004 
Bulté, I., & Onghena, P. (2012). When the truth hits you between the eyes: A software tool 
for the visual analysis of single-case experimental data. Meth Eur J Res Meth Behav 
Soc Sci, 8(3), 104-114. doi: 10.1027/1614-2241/a000042 
Burnett Heyes, S., Jih, Y. R., Block, P., Hiu, C. F., Holmes, E. A., & Lau, J. Y. (2015). 
Relationship Reciprocation Modulates Resource Allocation in Adolescent Social 
Networks: Developmental Effects. Child Dev, 86(5), 1489-1506. doi: 
10.1111/cdev.12396 
Constantino, J. N., Davis, S. A., Todd, R. D., Schindler, M. K., Gross, M. M., Brophy, S. L., . . 
. Reich, W. (2003). Validation of a brief quantitative measure of autistic traits: 
comparison of the social responsiveness scale with the autism diagnostic interview-
revised. J Autism Dev Disord, 33(4), 427-433. doi: 10.1023/a:1025014929212 
Creswell, W. J., & Plano Clark, V. L. (2011). Designing and conduction mixed methods 
research. (2nd ed.). Thousand Oaks, California, USA: Sage. 
Fein, D., Barton, M., Eigsti, I. M., Kelley, E., Naigles, L., Schultz, R. T., . . . Tyson, K. (2013). 
Optimal outcome in individuals with a history of autism. J Child Psychol Psychiatry, 
54(2), 195-205. doi: 10.1111/jcpp.12037 
Fombonne, E. (2018). Editorial: The rising prevalence of autism. J Child Psychol Psychiatry, 
59(7), 717-720. doi: 10.1111/jcpp.12941 
Franck, E., De Raedt, R., Barbez, C., & Rosseel, Y. (2008). Psychometric properties of the 
Dutch Rosenberg Self-Esteem Scale. Psychologica Belgica, 48(1), 25-35. doi: 
10.5334/pb-48-1-25 
Frazier, T. W., Youngstrom, E. A., Speer, L., Embacher, R., Law, P., Constantino, J., . . . 
Eng, C. (2012). Validation of proposed DSM-5 criteria for autism spectrum disorder. J 
Am Acad Child Adolesc Psychiatry, 51(1), 28-40.e23. doi: 10.1016/j.jaac.2011.09.021 
Fuller, E. A., & Kaiser, A. P. (2020). The Effects of Early Intervention on Social 
Communication Outcomes for Children with Autism Spectrum Disorder: A Meta-
analysis. J Autism Dev Disord, 50(5), 1683-1700. doi: 10.1007/s10803-019-03927-z 
Gillespie-Lynch, K., Kapp, S. K., Brooks, P. J., Pickens, J., & Schwartzman, B. (2017). 
Whose Expertise Is It? Evidence for Autistic Adults as Critical Autism Experts. Front 
Psychol 8(438). doi: 10.3389/fpsyg.2017.00438 
Heyvaert, M., Moeyaert, M., Verkempynck, P., Van den Noortgate, W., Vervloet, M., Ugille, 
M., & Onghena, P. (2017). Testing the Intervention Effect in Single-Case 
Experiments: A Monte Carlo Simulation Study. J Exp Educ, 85(2), 175-196. doi: 
10.1080/00220973.2015.1123667 
Kiresuk, T. J., & Sherman, R. E. (1968). Goal attainment scaling: A general method for 
evaluating comprehensive community mental health programs. Community Ment 
Health J, 4(6), 443-453. doi: 10.1007/bf01530764 
Kratochwill, T. R., Hitchcock, J., Horner, R. H., Levin, J. R., Odom, S. L., Rindskopf, D. M., & 
Shadish, W. R. (2010). Single-case designs technical documentation. .   Retrieved 17 
may 2020, from What Works Clearinghouse Website 
https://ies.ed.gov/ncee/wwc/Document/229 

NL 77902.091.21 Pegasus 
 
Version 2, date: 13-10-2021 
 
43 of 44 
Kvale, S., & Brinkmann, S. (2009). Interviews: learning the craft of qualitative research 
interviewing. Thousand Oaks, California, USA: Sage. 
Malinowski, K., Yee, C., Tevlin, J. M., Birks, E. K., Durando, M. M., Pournajafi-Nazarloo, H., . 
. . McKeever, K. H. (2018). The Effects of Equine Assisted Therapy on Plasma 
Cortisol and Oxytocin Concentrations and Heart Rate Variability in Horses and 
Measures of Symptoms of Post-Traumatic Stress Disorder in Veterans. J Equine Vet 
Sci, 64, 17-26. doi: 10.1016/j.jevs.2018.01.011 
Malter Cohen, M., Tottenham, N., & Casey, B. J. (2013). Translational developmental studies 
of stress on brain and behavior: implications for adolescent mental health and illness? 
Neuroscience, 249, 53-62. doi: 10.1016/j.neuroscience.2013.01.023 
Manly, B. F. J. (2007). Randomization Tests, 4th Edition by Eugene S. Edgington, Patrick 
Onghena. Int Stat Rev, 75(2), 269-269. doi: 10.1111/j.1751-5823.2007.00015_21.x 
Mazefsky, C. A. (2015). Emotion Regulation and Emotional Distress in Autism Spectrum 
Disorder: Foundations and Considerations for Future Research. J Autism Dev Disord, 
45(11), 3405-3408. doi: 10.1007/s10803-015-2602-7 
Mazefsky, C. A., Borue, X., Day, T. N., & Minshew, N. J. (2014). Emotion regulation patterns 
in adolescents with high-functioning autism spectrum disorder: comparison to typically 
developing adolescents and association with psychiatric symptoms. Autism Res, 7(3), 
344-354. doi: 10.1002/aur.1366 
Mazefsky, C. A., Yu, L., & Pilkonis, P. A. (2020). Psychometric Properties of the Emotion 
Dysregulation Inventory in a Nationally Representative Sample of Youth. J Clin Child 
Adolesc Psychol, 1-13. doi: 10.1080/15374416.2019.1703710 
Mazefsky, C. A., Yu, L., White, S. W., Siegel, M., & Pilkonis, P. A. (2018). The emotion 
dysregulation inventory: Psychometric properties and item response theory calibration 
in an autism spectrum disorder sample. Autism Res, 11(6), 928-941. doi: 
10.1002/aur.1947 
McDaniel Peters, B. C., & Wood, W. (2017). Autism and Equine-Assisted Interventions: A 
Systematic Mapping Review. J Autism Dev Disord, 47(10), 3220-3242. doi: 
10.1007/s10803-017-3219-9 
Mengler, L., Khmelinskii, A., Diedenhofen, M., Po, C., Staring, M., Lelieveldt, B. P., & Hoehn, 
M. (2014). Brain maturation of the adolescent rat cortex and striatum: changes in 
volume and myelination. Neuroimage, 84, 35-44. doi: 
10.1016/j.neuroimage.2013.08.034 
Mogensen, L., & Mason, J. (2015). The meaning of a label for teenagers negotiating identity: 
experiences with autism spectrum disorder. Sociol Health Illn, 37(2), 255-269. doi: 
10.1111/1467-9566.12208 
Nader-Grosbois, N., & Mazzone, S. (2014). Emotion Regulation, Personality and Social 
Adjustment in Children with Autism Spectrum Disorders. Psychology, 5, 1750-1767. 
doi: 10.4236/psych.2014.515182 
Patton, M. Q. (2015). Qualitative research & evaluation methods: Integrating theory and 
practice. Thousand Oaks, California, USA: Sage. 
Peters-Scheffer, N., Didden, R., Korzilius, H., & Sturmey, P. (2011). A meta-analytic study on 
the effectiveness of comprehensive ABA-based early intervention programs for 
children with Autism Spectrum Disorders. Res Autism Spectr Disord, 5, 60-69. doi: 
10.1016/j.rasd.2010.03.011 

NL 77902.091.21 Pegasus 
 
Version 2, date: 13-10-2021 
 
44 of 44 
Reichow, B. (2012). Overview of meta-analyses on early intensive behavioral intervention for 
young children with autism spectrum disorders. J Autism Dev Disord, 42(4), 512-520. 
doi: 10.1007/s10803-011-1218-9 
Rosenberg, M. (1979). Conceiving the self: Basic Books. 
Samson, A. C., Wells, W. M., Phillips, J. M., Hardan, A. Y., & Gross, J. J. (2015). Emotion 
regulation in autism spectrum disorder: evidence from parent interviews and 
children's daily diaries. J Child Psychol Psychiatry, 56(8), 903-913. doi: 
10.1111/jcpp.12370 
Sussman, D., Leung, R. C., Vogan, V. M., Lee, W., Trelle, S., Lin, S., . . . Taylor, M. J. 
(2015). The autism puzzle: Diffuse but not pervasive neuroanatomical abnormalities 
in children with ASD. Neuroimage Clin, 8, 170-179. doi: 10.1016/j.nicl.2015.04.008 
Swain, D., Scarpa, A., White, S., & Laugeson, E. (2015). Emotion Dysregulation and Anxiety 
in Adults with ASD: Does Social Motivation Play a Role? J Autism Dev Disord, 45(12), 
3971-3977. doi: 10.1007/s10803-015-2567-6 
Trzmiel, T., Purandare, B., Michalak, M., Zasadzka, E., & Pawlaczyk, M. (2019). Equine 
assisted activities and therapies in children with autism spectrum disorder: A 
systematic review and a meta-analysis. Complement Ther Med, 42, 104-113. doi: 
10.1016/j.ctim.2018.11.004 
Van Den Noortgate, W., & Onghena, P. (2003). Estimating the mean effect size in meta-
analysis: bias, precision, and mean squared error of different weighting methods. 
Behav Res Methods Instrum Comput, 35(4), 504-511. doi: 10.3758/bf03195529