BackgroundAlthough observer-rated instruments assessing therapist's adherence to relapse-preventive treatments are available, they do not adequately cover specific relapse-preventive elements that focus on implementation of strategies after terminating treatment. This study describes the development of the KERI-D (Kodierbogen zur Erfassung Rückfallprophylaktischer Interventionen bei Depression/Coding System to Assess Interventions of Relapse Prevention in Depression). The KERI-D is a new observer-based rating tool for acute or continuation/maintenance-phase sessions and assesses relapse-prevention elements including implementation into patient's daily routines. MethodsThe development of the KERI-D included iterative steps referring to theoretical, clinical and empirical sources. It consists of 19 content items within four categories (self-care, early warning signs, triggering events/situations, termination of therapy) and one global item. For empirical analyses, videotaped psychotherapy sessions of 36 psychotherapies were rated by three independent observers and analyzed for their psychometric properties. ResultsMost items showed moderate to good inter-rater reliability (median ICC = .80) and retest reliability (median ICC = .93). Principal-axis factor analysis revealed three subscales, and first evidence of content validity was demonstrated. No associations with clinical follow-up data were found. LimitationsAnalysis was limited to a relatively small sample of selected psychotherapy sessions. Evaluation of predictive validity is a desirable next step to further examine applicability and scope of the instrument. ConclusionsThe KERI-D is the first observer-based rating instrument measuring specific relapse-prevention strategies in psychotherapy for depression. It may help to identify elements that prove effective in reducing relapse/recurrence in the long-term and thereby help to optimize effect duration of depression treatment.