Introduction

The concept of personality, pivotal in psychodynamic psychotherapy, continues to evolve. Maladaptive personality functioning, which involves identity (related to uniqueness/boundaries, self-esteem, and emotion regulation), self-direction (involving goals, norms, and self-reflection), empathy (related to understanding others, perspectives, and impact), and intimacy (involving connectedness, closeness, and cooperation/mutuality), as well as emotional control, impulse regulation, and interpersonal difficulties, falls within the spectrum of personality disorders (Karterud & Kongerslev, 2020). These problems encompass the identity, self-direction, empathy, and intimacy domains (Criterion A of the Alternative Model for Personality Disorders, AMPD of the Diagnostic and Statistical Manual of Mental Disorders, DSM-5, APA, 2014). It has been stated that personality development is influenced by early childhood experiences, with adverse experiences linked to impaired functioning (Kampling et al., 2022; Karterud & Kongerslev, 2020; Luyten & Fonagy, 2022; Luyten et al., 2020; Mulder & Tyrer, 2019; Watters et al., 2019). Secure attachment experiences are crucial for healthy personality development, highlighting the overlap between CPTSD and personality disorders (Kovács et al., 2020). The ambiguity among diagnostic categories has spurred exploration of alternative approaches, emphasizing dimensional evaluation and personality-matched interventions (Papamalis et al., 2020; Zimmermann et al., 2019).

Based on current evidence, it is indicated that personality functioning can be modified to become more adaptive through psychotherapy (Luyten & Fonagy, 2022). Individuals exhibiting more maladaptive levels experience poorer treatment outcomes and a higher probability of discontinuing treatment (Papamalis et al., 2020). The role of personality functioning within the treatment process can contribute to identifying the individual course of treatment. This implies that despite ‘stable’ personality traits, treatment interventions could moderate the degree of dysfunctional behavior by targeting partially context-sensitive characteristic adaptations, as implied by Karterud and Kongerslev's (2020) postulation of personality. The approach to treating personality problems varies depending on severity, ranging from supportive interventions to interpretative interventions (Bach & Simonsen, 2021). Schema-focused therapy, Dialectical Behavior Therapy, and Mentalization-Based Therapy are current designated treatment interventions for personality dysfunction (AkwaGGZ, 2022). The treatment approach for addressing personality dysfunction involves supporting the therapeutic alliance, assessing the risk of self-harm or harm to others, enhancing mentalization abilities, and emphasizing the importance of strengthening one's identity or sense of self (Bach & Simonsen, 2021). Furthermore, Bales et al. (2015) found in their study utilizing a dimensional personality approach that all five facets of personality functioning, as measured by the Severity Indices of Personality Problems (SIPP), showed improvement after therapy. Similarly, Verheul et al. (2008) found in their study on personality functioning that self-control, identity integration, and responsibility levels demonstrated gradual improvement over a 3-year psychotherapy duration.

As previously noted, fostering a strong therapeutic alliance between patient and therapist is crucial (Bach & Simonsen, 2021). The therapeutic alliance's significance as a predictor of treatment effectiveness is well-established, with interpersonal functioning influencing its strength (Prusiński, 2023; Bach & Simonsen, 2021; Del Re et al., 2021; Dolev & Zilcha-Mano, 2019). Debate persists over whether the alliance itself is therapeutic or facilitates effective treatment, with evidence suggesting its moderating effect on therapeutic outcomes (Dolev & Zilcha-Mano, 2019).

Despite symptom remission over time, individuals with personality problems often still experience impaired psychosocial functioning. Additionally, the effect sizes of psychotherapy outcomes across various schools of psychotherapy and psychiatric disorders seem to be stagnating or even decreasing (Balder et al., 2024; Leichsenring et al., 2019). As a result, the evidence-based approach to treatment development has primarily focused on symptomatic descriptors, revealing its limitations (Karterud & Kongerslev, 2020; Zanarini et al., 2018; Zeitler et al., 2020). Consequently, psychotherapy research is now prioritizing the quest for more personalized approaches. One avenue of research in this endeavor lies in Equine-assisted psychotherapy, a subset of Animal-Assisted Psychotherapy (AAP), which explores ways of enhancing the psychotherapeutic process by involving animals to improve outcomes.

Equine-Assisted Psychotherapy

Equine-assisted psychotherapy (EAP) adheres to evidence-based psychotherapy principles (Kovacs et al., 2022; IAHAIO, 2014; Fine, 2019; Parish-Plass, 2020), drawing from various theoretical frameworks like psychodynamic, trauma-focused, attachment-based, and interpersonal approaches (Kovács, 2018). In EAP, horses form part of a therapeutic triad, aiding the therapeutic relationship and psychological processes through experiential activities guided by a therapist. These activities deepen understanding of patients' patterns from both interpersonal and intrapersonal perspectives (Centonze et al., 2021, 2023), eliciting authentic emotional responses and sensory experiences (Kovacs et al., 2022). The size and strength of horses can trigger specific behaviors and projections from patients. Experiences such as being carried by a horse can offer passive regulation reminiscent of early parent–child interactions (Kovacs et al., 2022). Horses, as social animals with unique personalities living in herds, reflect human social dynamics (VanFleet & Faa-Thompson, 2017). Involving patients in interactions with animals in psychotherapy helps them remain present, fostering calmness in the limbic system and promoting connections between the brain hemispheres, facilitating better integration of causal explanations with emotional and sensory experiences, thus enhancing mentalization skills (Parish-Plass, 2020; Williams, 2018). Research supports the effectiveness of Equine-assisted Short-Term Psychodynamic Psychotherapy (ESTPP) in addressing attachment themes (Kovács et al., 2021, 2022), indicating its potential to enhance personality functioning and psychotherapy outcomes related to self-control, identity integration, responsibility, relational capacities, and social concordance.

Little is known about the influence of personality functioning on outcomes in animal-assisted psychotherapy and its potential benefits (Kovács et al., 2020). This study aims to investigate the potential impact of personality functioning levels on the outcome of psychotherapy, specifically the degree of psychological dysfunction by comparing the associated effects between ESTPP and TAU. Additionally, it aims to examine the changes in personality functioning levels and psychological dysfunction levels before and after accounting for the therapeutic alliance.

Method

Design

The study examined the effects of ESTPP using an explorative non-randomized pre- and post treatment design, with two intervention groups (ESTPP versus TAU). In both conditions, the psychotherapy was terminated around (but not later than) 12 months after the start of treatment. Measurements were taken at the start of the psychotherapy (t0) and at 12 months after the start (t1). The therapeutic alliance was typically measured 3 months after start of psychotherapy.

Participants and Procedure

Inclusion and Exclusion Criteria

Participants were recruited from two mental health care centers in the Netherlands: Ars Curae/SPEL Psychologen Putten (AC), offering ESTPP, and Zaans Medisch Centrum (ZMC), offering Treatment as Usual (TAU). Both centers share a psychodynamic psychotherapy approach and have mutual patient referrals. Referrals were made by general practitioners, with diagnoses and therapy indications established during intake procedures. Patients typically present with severe and complex intrapsychic and interpersonal issues according to DSM-5 criteria. Informed consent was obtained from participants prior to inclusion, adhering to the Declaration of Helsinki guidelines. Eligible participants were 18 years or older, with those in the experimental group required to travel independently. All participants had attachment-related personality problems, with exclusion criteria including inadequate psychological stability due to suicidal behavior, psychosis, or substance abuse.

For the ESTPP condition 92 participants were enrolled. Of these, N = 74 (80.4%) were female, and the mean age was 37 years (SD = 12.3), ranging from 17 to 63 years. There were 107 participants in the TAU condition, N = 78 (80.4%) were female, and the mean age was 30.5 years (SD = 10.8), ranging from 17 to 58 years. Data from the participants of TAU were obtained from the SPECTRE study, an extensive multicenter study on psychotherapy effectivity in patients with personality disorders (Bartak et al., 2007, 2010). The study was approved by the Medical Ethics Committee of the VU University Amsterdam Medical Center in the Netherlands.

Measurements

Psychological dysfunction was measured using the Dutch version of the Brief Symptom Inventory (BSI; De Beurs & Zitman, 2006; De Beurs et al., 2007), a validated self-report scale derived from the revised Symptom Checklist-90 (Arrindell & Ettema, 2003; Derogatis & Melisaratos, 1983).The BSI consists of 53 items and a 5-point Likert scale, ranging from 1 (not at all) to 5 (extremely). Rankings characterize the intensity of distress during the past 7 days. The total score on the psychological dysfunction scale was used in this study. A higher score indicates more severe dysfunction. The BSI is a useful tool for measuring progress during and after psychotherapy and has been shown to have good validity and reliability, with a Cronbach’s α of 0.96 (De Beurs et al., 2007).

Personality functioning was measured using the Severity Indices of Personality Problems short form (SIPP-SF) (Verheul et al., 2008). The SIPP-SF consists of a 60 item dimensional self-report measure to assess 16 facets clustered into five higher-order ‘broad’ domains on a 4-points scale, ranging from 1 = fully disagree, 2 = partly disagree, 3 = partly agree, 4 = fully agree and referring to the last 3 months. The five higher-order domains with their facets are: Self-control = emotion regulation, effortful control; Identity integration = self-respect, stable self-image, self-reflexive functioning, enjoyment, purposefulness; Responsibility = responsible industry, trustworthiness; relational capacities = intimacy, enduring relationships, feeling recognized; Social concordance = aggression regulation, frustration tolerance, cooperation, respect. High scores indicate better adaptive functioning. The SIPP has demonstrated good validity in several countries in clinical and nonclinical populations (Arnevik et al., 2009; Feenstra et al., 2011).

The therapeutic alliance was measured using the Working Alliance Inventory (WAI) and Helping Alliance Questionnaire (HAQ). The WAI consists of 12 items rated on a 5-point scale. The questionnaire measures three dimensions: the therapeutic relationship, agreed-upon therapeutic goals, and therapeutic tasks (Horvath & Greenberg, 1989). The used Dutch version of the WAI demonstrated good reliability and validity (Paap et al., 2019; Stinckens et al., 2019). The Helping Alliance Questionnaire (HAQ), like the WAI, is a tool used to assess the quality of the therapeutic relationship from the patient's point of view. It consists of 19 items rated on a 6-point scale. The HAQ has been found to have good reliability and validity (Luborsky et al., 1996). The results of the WAI and HAQ were pooled and standardized with z-scores. A cutoff score of 3.45 for WAI and 4.14 for HAQ was used meaning qualitatively good or positive therapeutic alliance to compare for quality of the therapeutic alliance.

Intervention

ESTPP was administered through a 1-week intensive individual inpatient module at a ranch in Spain/France, followed by outpatient sessions in the Netherlands over 12 months. The module comprised four 2-h daily sessions, and outpatient sessions were 1 h long at descending frequency (assessed by the treatment team), up to the end of the trajectory (12 months, approximately 25 sessions). The trajectory consisted of a diagnostic or stabilization phase, a focal phase, a consolidation phase, and termination phase. The trajectory had an experiential character in which the therapists, who are additionally trained by animal experts, reflected on what was occurring between the patient, the horse, and the therapist (Kovács, 2018). The sessions were well-structured, with a balance between therapeutic exercises and rest, with set eating and feeding times for respectively patient and animals. Exercises with the horses—alongside as well as on the horse—consist of guided tasks in observation, (physical) contact, tuning into the affective state of the horse, finding synchronicity and dealing with the instantaneous feedback of the horse, leadership, congruence, body posture, ‘letting go’, relaxation, concentration, setting boundaries, dealing with fear and longing, balance and taking control, taking care of oneself and the animal. These experiences in the patient's here-and-now are metaphorically related to patient’s daily life and core-conflict with the help of the therapist (Kovács, 2018). The control condition, TAU, involved multimodal inpatient group psychotherapy over 9–12 months, for 3 days/week incorporating Short Term Psychodynamic Psychotherapy and expressive therapies like art and psychomotor therapy, conducted 3 days/week in the Netherlands.

Statistical Analysis

IBM SPSS Statistics for Windows, Version 27 was used IBM Corporation, Armonk, USA (IBM Corporation, Armonk, NY, USA). Descriptive analyses in SPSS characterized the study population. Linear mixed models with random intercepts were employed to estimate the intervention effect, accommodating repeated measurements within participants. These models address complexities and variations in treatment effects across multiple outcome variables and time points within a relatively small sample.

To assess the effects of ESTPP and TAU on psychological dysfunction as dependent variable, a mixed model that accounted for repeated measures within the participants was built as a basic model with fixed effects for group (ESTPP- compared to TAU-condition) and time (time-point t1 compared to t0). This model was extended with both two- and three-way interaction terms for time points, intervention condition, personality functioning and therapeutic alliance (as ordinal variables, fixed effects) as predictors. The interaction terms were personality functioning × time, personality functioning × group (intervention condition), group × time, personality functioning × time × group and therapeutic alliance × group, and therapeutic alliance × time. Subsequently, to assess the effects of the intervention condition on personality functioning (dependent variable) additional models were built. These models accounted for repeated measures and included fixed effects for group (ESTPP- compared to TAU-condition), time (t1 compared to t0), and therapeutic alliance as predictors. All models were adjusted for age and sex.

When personality functioning was missing at baseline, we imputed the scores with available posttreatment scores that can be regarded as a conservative approach reflecting no changes in personality functioning. Patients were included in analyses if they had a non-missing psychological dysfunction score and a non-missing score on at least one score of the personality functioning. The scores on the questionnaires were transformed into standardized values to improve comparability using the mean value and the standard deviation at t0. For example, interaction personality × time represents the effect at postintervention with personality function score of 1 SD at baseline (standardized scores); interaction personality × group represents the effect for ESTPP compared to TAU when personality functioning equals 1 SD at baseline. The two-tailed significance level was set at α = 0.05.

Results

Table 1 shows the baseline data. The total sample consisted of n = 199 patients.

Table 1 Descriptives study population at baseline
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Table 2 shows the difference between ESTPP and TAU regarding psychological dysfunction. Both intervention conditions demonstrated a decrease in psychological dysfunction scores over time, as indicated by the basic model with the time predictor showing an estimated effect of − .5 [− .7 to − .3], p < .001. Notably, the ESTPP condition exhibited higher psychological dysfunction scores at both time points, as shown in the basic model with the group predictor and an estimated effect of .9 [.6 to 1], p < .001. Furthermore, although both groups experienced changes in psychological dysfunction over time, the rate of change did not differ between the two groups. Age (not shown in Table 2) did seem to have a significant effect on psychological dysfunction in this basic model as age increases, psychological dysfunction tends to decrease (estimated effect, − .01 [95% CI − .02 to .00], p = .04).

Table 2 Results mixed models on psychological dysfunction accounting for personality functioning domain, time and ESTPP compared to TAU (group)
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The adjusted models with personality functioning variables as predictors showed that for all personality functioning domain scores (self-control, identity integration, responsibility, relational capacities and social concordance) that increases in these scores were associated with decreases in psychological dysfunction (Table 2). We found significant interaction effects for self-control × time and identity integration × time that imply that these personality functioning domains may weaken the improvements of psychological dysfunction between t0 and t1 in both conditions.

We observed significant interaction effects for group × personality domain for all domains but self control. This indicates that with higher scores on personality functioning domains, except for self-control, patients in ESTPP condition had less psychological dysfunction. However, all three-way interaction terms (personality × group × time) were not significant, which implies that the changes in psychological dysfunction over time were not differently influenced by personality in the ESTPP condition compared to TAU. Age and gender were not associated with scores on psychological dysfunction in these models except for the model with social concordance, where an increase in age was weakly associated with a significant decrease of psychological dysfunction (estimated effect, − .02 [95% CI − .03 to − 3.5], p = .05).

The models that examined the effects on personality functioning domains (as dependent variables) revealed increased scores at t1 compared to t0 in both ESTPP and TAU conditions for self-control, identity integration, responsibility, and relational capacities. No effect of time was observed for social concordance (see first column in Table 3). Furthermore, the change in personality functioning was not different for ESTPP and TAU for all domains but identity integration. For identity integration, the improvement of 0.5 at t1 disappears in the ESTPP condition with identity integration scores larger than 1 SD (estimated effect for the interaction time × group, − .5 [− 1 to .01], p = .04, Table 3). Age and gender seemed to be associated with scores on responsibility, i.e. as age increases responsibility scores tend to increase (estimated effect, .01 [.00 to .02], p = .02) and the responsibility scores of men seem to be lower than those of women (estimated effect, − .4 [− .7 to − .08], p = .02).

Table 3 Results mixed models for the effects in personality functioning domains when accounting for time points, and ESTPP compared to TAU (group)
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The models built to assess the effects of the therapeutic alliance on psychological dysfunction (as dependent variable) and personality functioning domain (as dependent variable), revealed non-significant effects of therapeutic alliance. Meanwhile, cut-off scores of > 2.45 for WAI and > 4.14 for HAQ indicated a qualitatively good or positive therapeutic alliance (Table 1).

Discussion

The aim of this study was to investigate the potential impact of personality functioning domain levels on psychotherapy outcomes. Psychological dysfunction levels, measured with the BSI, served as the outcome measure for patients with intra- and interpersonal problems undergoing ESTPP. Additionally, the study aimed to explore changes in personality functioning domain levels and psychological dysfunction levels before and after considering the therapeutic alliance. To our knowledge, this study is the first to examine this relationship in the field of AAP, thus extending previous research on personality functioning associated with outcome and contributing to the body of evidence in AAP.

Our results showed a decline in psychological dysfunction scores over time for both intervention conditions. However, the ESTPP group exhibited higher psychological dysfunction scores at both pre- and post-treatment compared to TAU, with nearly one standard deviation difference between the two. Despite this initial disparity, both groups demonstrated similar progress during psychotherapy. This finding aligns with broader research on treatment outcomes, suggesting parity in effectiveness across different psychotherapies (Fonagy, 2015). Although the ESTPP group showed a greater reduction in psychological dysfunction post-intervention, this difference was not statistically significant. Larger participant groups or more extensive investigations may be needed to establish definitive trends in psychological dysfunction within the ESTPP group over time. It's possible that individuals seeking ESTPP often have heightened psychological distress, similar to patients with personality problems, which could manifest as resistance to change (Bach & Simonsen, 2021). This highlights the potential benefit of equine-assisted psychotherapy for highly distressed patients, supporting the idea of tailoring treatments to individual needs in line with Leichsenring et al.'s (2019) perspective. Moreover, exploring the complementarity and benefits of ESTPP as an add-on intervention, as investigated by Kovacs et al. (2021), could offer valuable insights for further study.

The results of this study align with previous research on personality functioning and psychotherapy outcomes. Typically, individuals with higher levels of self-esteem, empathy, conscientiousness, and openness tend to experience better psychotherapy outcomes (Papamalis et al., 2020). In this study, higher levels of personality functioning also correlated with a lesser degree of psychological dysfunction. This suggests that individuals with better personality functioning at the start of psychotherapy tend to benefit more, underscoring the importance of addressing personality functioning during both equine-assisted psychotherapy and TAU.

Both conditions exhibited decreased levels of self-control and identity integration after therapy, which may suggest increased self-reflection and distress among patients (significant interaction effects for self-control × time and identity integration × time). This observation could result in heightened feelings of distress or sadness, reminiscent of the concept of “sadder but wiser” (Sattel et al., 2012). Specifically, in ESTPP, interactions with the horse might intensify confrontations with aspects of identity, prompting patients to acknowledge recurring self-image challenges. Although not statistically significant, there is an emerging trend linking higher levels of responsibility and relational capacities with increased psychological dysfunction over time. These intrapsychic aspects may pose challenges to mentalization skills during psychotherapy (Jewell et al., 2021).

No significant three-way interaction effects (group × time × personality functioning) were observed, indicating no specific advantage of one intervention over the other. Generally, ESTPP patients displayed higher scores on personality functioning domains, except for self-control, and less psychological dysfunction compared to TAU (group × personality functioning). The effectiveness of ESTPP in reducing psychological dysfunction may vary depending on initial personality functioning, highlighting the importance of assessing personality when selecting an intervention. Self-control, considered a behavioral facet, showed similar effects on distress reduction in both conditions. However, identity integration, an intrapsychic aspect targeted by ESTPP (Kovács et al., 2021), notably influenced psychological dysfunction scores, with ESTPP showing lower scores compared to TAU. This suggests that ESTPP may particularly address identity integration, impacting patient well-being. Further research is needed to explore ESTPP's potential in delving deeper into intrapsychic aspects.

Our study's findings align with previous research by Bales et al. (2015) and Smits et al. (2020), indicating improved personality functioning during psychotherapy. Identity integration emerged as a significant factor, consistent with the therapeutic focus on identity (Bogaerts et al., 2021). Both ESTPP and TAU led to enhanced identity integration compared to baseline, but the rate of improvement varied between conditions. Patients with higher identity integration scores in ESTPP showed comparatively lesser improvement, possibly due to their initially higher levels. However, identity integration had a more pronounced impact on psychological dysfunction within ESTPP. The observed prominence of self-control and identity integration may mutually influence each other, with a robust identity contributing to self-regulation and vice versa (Guo et al., 2022).

While social concordance influenced psychological dysfunction during psychotherapy in our study, we observed no significant changes in this aspect of personality functioning over time in either condition, consistent with findings by Papamalis et al. (2020). Social concordance encompasses social (re)integration skills, which might require more time or attention during psychotherapy. Smits et al. (2020) suggested the need for patients to generalize therapy learnings to real-world situations, promoting independence and regulation in daily challenges outside the psychotherapy setting.

In contrast to prior literature (Prusiński, 2023; Bach & Simonsen, 2021; Del Re et al., 2021; Dolev & Zilcha-Mano, 2019), our study found no significant association between the therapeutic alliance and outcome variables, including personality functioning. This suggests that the therapeutic alliance reached a beneficial level by the time of measurement, given baseline cutoff scores, and improvement across personality functioning. While we did not assess drop-outs, future research should explore this, as maladaptive personality functioning is linked to therapy attrition. The therapeutic alliance may have been equally beneficial in both conditions due to group member interaction in TAU (Hestbæk et al., 2022) and animal interaction in ESTPP (Parish-Plass, 2020), potentially outweighing patient–therapist interaction measured by the questionnaire. Additionally, our study did not identify a specific therapeutic advantage solely attributed to the therapeutic alliance, warranting further investigation into this relationship.

Limitations of the Study and Future Directions

Firstly, this study exclusively relied on self-report instruments, lacking therapists' observations of patient progress, which could have provided an alternative perspective. Additionally, there was no data on therapy fidelity or adherence, despite certified therapists administering the interventions. Secondly, despite using an imputation strategy for missing data, the sample size (N) remained relatively low. However, the conservative imputation approach yielded comparable results. Thirdly, the absence of significant three-way interactions hinders drawing strong conclusions about treatment preferences or predictors over time. Future studies with larger sample sizes may yield significant interactions. Fourthly, the potential contribution of pharmacotherapy to observed improvements was not accounted for, as medication use during treatment was not included in the analyses. Fifthly, implementing a randomized design in this naturalistic study, given the unique features of AAP, presents challenges. However, future studies should consider randomized strategies for more targeted outcomes, although the naturalistic design offers enhanced external validity. Furthermore, the TAU condition, a well-established psychotherapy (Bartak et al., 2010), enables a comprehensive comparison. Lastly, despite the conceptual overlap between functioning and traits, using personality function levels as a baseline measure to explore the impact of personality malfunction on psychotherapy outcome was justified (Bach & Hutsebaut, 2018). Future research should delve into the influence of personality functioning changes during long-term treatment to identify specific predictors for more personalized treatment strategies. Additionally, future studies should explicitly examine the influence of animals in psychotherapeutic domains, akin to the therapeutic alliance in EAP.

Clinical Implications

Psychotherapy providers should be prepared to offer additional clinical attention and support for individuals with dysfunctional levels of personality functioning, especially focusing on self-control and identity. Previous research underscores the significance of addressing identity in understanding personality disorders dimensionally (Bogaerts et al., 2021). Deficiencies in self-control and identity integration increase susceptibility to psychological distress, such as the development of CPTSS (Kampling et al., 2022). Thus, it's crucial to equip staff with the necessary skills for targeted interventions addressing these personality functions to ensure appropriate treatment. Certain domains like identity integration and social concordance may require longer psychotherapy duration beyond a 12-month period to reach healthier levels (Verheul et al., 2008).

Recognizing the therapeutic benefits of experiential psychotherapy for individuals with personality dysfunction (Centonze et al., 2021, 2023), this study suggests that Equine-assisted Short Term Psychodynamic Psychotherapy (ESTPP), as a profoundly experiential approach, has the potential to create a novel narrative through the horse. This experiential method can aid individuals in cultivating a more integrated sense of self, emphasizing the importance of identity development (Lind et al., 2022). Despite higher initial psychological dysfunction in the ESTPP group, both ESTPP and TAU exhibited similar reductions in psychological dysfunction, implying that highly distressed patients may benefit from experiential therapies like ESTPP. The intensified nonverbal interaction with horses likely contributes to these therapeutic benefits, highlighting the potential of experiential approaches in treating personality dysfunction.

Conclusion

The findings suggest that Equine-assisted short-term Psychodynamic Psychotherapy (ESTPP) yields outcomes comparable to treatment-as-usual (TAU), with both influenced by levels of personality functioning, particularly in the domains of self-control and identity integration. ESTPP may offer specific benefits to patients grappling with high psychological distress due to maladaptive personality functioning, aligning with the call for personalized interventions. The unique dynamics of horse interaction, including their individual personality traits, could facilitate acceptance despite the confrontational aspect, fostering a supportive therapeutic environment. The improvement observed in psychological dysfunction and personality functioning across both conditions underscores the importance of further exploration and application of ESTPP in appropriate therapeutic settings.