Fluctuations of dissociation and inner tension during inpatient dialectical behavior therapy: associations with self-injury and suicidal ideation

Background In Dialectical Behavior Therapy (DBT), monitoring inner tension and state dissociation is considered helpful for understanding a patient’s affective and behavioral responses, especially regarding self-harming behaviors. This study aims to investigate how potentially aversive internal states including dissociation, inner tension and fluctuations of tension, i.e. affective instability, during the initial phase of inpatient DBT relate to self-injury, suicidal ideation, and symptom reduction. Methods 41 patients with personality disorder (borderline or combined), undergoing an 8-week inpatient DBT program used a smartphone application for ecological momentary assessment of inner tension and state dissociation. We assessed the Borderline Symptom List (BSL-23) upon admission and discharge, self-injury during the inpatient stay, and the intensity of suicidal ideation per day (diary card ratings) retrospectively from digital patient files. We employed linear mixed models to analyze the trajectories of inner tension, affective instability (i.e. squared difference between consecutive inner tension ratings), and state dissociation over the initial 3 weeks of therapy and variability across hours, as well as daily associations with the intensity of suicidal ideation. We used logistic regression to examine if aversive internal states are associated with the occurrence of self-injury during DBT. Results We found a slight reduction in state dissociation, affective instability, and high levels of inner tension during the initial 3 weeks of therapy. Analyses of intraday data showed a slight increase in state dissociation from morning to midday and self-injury during DBT was associated with slightly higher mean dissociation levels. On days with greater intensity of suicidal ideation, elevated inner tension and state dissociation levels were found while affective instability was not related to self-injury or suicidal ideation. Changes in BSL-23 over therapy were not related to aversive internal states during the initial therapy phase. Conclusion Aversive internal states decreased early in inpatient DBT, with midday emerging as a critical time for dissociation management. Daily increases in state dissociation and inner tension might serve as warning signs for suicidality and our data confirm the utility of their monitoring in self-harm prevention. When state dissociation is therapeutically addressed during DBT as in the program investigated, it does not seem to hamper improvement in borderline symptoms. Trial registration Retrospectively registered - https://osf.io/dfq9y/?view_only=4c19b891bb6448009b22f60b2552bd73. Supplementary Information The online version contains supplementary material available at 10.1186/s40479-026-00339-1.