Attachment characteristics play a key role in mental health and in understanding mental disorders. The aim of this study was to gain insight into the role the attachment characteristics can play in treatment effects in adult patients with intrapsychic and interpersonal problems who underwent Equine-assisted Short-term Psychodynamic Psychotherapy (ESTPP). In the first part of the study, we compared the effects of ESTPP to treatment-as-usual from a previous dataset regarding psychological dysfunction. For this, an explorative experimental non-randomized pre-treatment and 1-year post-treatment design was used. A mixed model revealed a significant decline in psychological dysfunction for both conditions, with no significant difference between the two. In the second part of the study, we examined the course of ESTPP effects over the period of 1 year when controlled for attachment styles and, subsequently, for internal working models of self and others. To this end, measurements were taken at baseline, 2 months waiting time, one-week intensive module, 6 months, and one year after the start of the treatment. Mixed models accounted for repeated measures showed significant improvements in psychological dysfunction, remoralization, and depression for ESTPP patients over time. The study implies that models of self and others may be used to predict the course of effects, which is relevant in determining what works for whom. In particularly, duration and intensity of therapy and a focus on the Model of Self seem relevant for shaping a more personalized treatment. ESTPP seems beneficial for patients with low pre-treatment attachment security.
Keywords: attachment; equine-assisted psychotherapy; internal working models; psychodynamic; trauma.