Oral Presentation

Objective: Acute, recurrent, or long-lasting traumatic experiences may lead to various enduring changes in individuals.Moreover, exposure to early interpersonal traumatic events or multiple trauma experiences can result in more complex clinical presentations that go beyond posttraumatic stress disorder (PTSD) symptoms and are defined as Complex Post-Traumatic Stress Disorder (CPTSD) (Cloitre et al., 2009;Herman, J. L. 1992;van der Kolk et al., 2005).Complex trauma encompasses not only PTSD symptoms but also marked difficulties in interpersonal functioning (World Health Organization [WHO], 2018).The aim of the present study is to examine within-person changes in interpersonal problems, depression-anxiety-stress, valued living, and experiential avoidance following an eight-session Acceptance and Commitment Therapy (ACT) intervention among individuals with complex trauma.Method: This study was conducted using a nonconcurrent multiple baseline design, one of the single-case experimental designs.Accordingly, eight participants were included.In addition to the daily individual measurement items assessing experiential avoidance, value-directed behavior, and interpersonal problems, participants completed standardized measures at pre-test and post-test.These standardized measures included the Clinician-Administered PTSD Scale (CAPS-5), Acceptance and Action Questionnaire (AAQ-II), the Depression Anxiety Stress Scales-Short Form (DASS-21), the Engaged Living Scale (ELS), and the Inventory of Interpersonal Problems Circumplex Scales (IIP-C).For data analysis, visual analysis and Tau-U analysis were used for daily measurements, while clinically significant change and the reliable change index were used for standardized measures.Ethical approval was obtained for the study from the Istanbul Medipol University Ethics Committee (Approval Date: 03/