Abstract
This systematic review investigates the long-term trajectories of depressive symptoms in individuals with acquired brain injury (ABI) and identifies factors predicting group membership in these trajectories. The review follows the PRISMA guidelines and is registered on the International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY-2023–11-0013). A comprehensive search of MEDLINE, PSYCINFO, EMBASE, CINHALPlus, ScienceDirect, Scopus, and Web of Science identified peer-reviewed studies published in English on adults aged 16 and above with an ABI diagnosis. Studies were included if they used a validated depression measure, had at least three assessment points, and applied group-based trajectory modelling. Exclusion criteria included studies focusing on neurodegenerative or neurodevelopmental disorders, or solely on treatments. The methodological quality was assessed using Joanna Briggs’ critical appraisal tool. The review synthesised data from ten studies involving 13,205 participants (average age 51.38 years, 55.86% male). Four depressive symptom trajectory groups were identified with varying prevalence: stable low (68%), persistent high (13%), increasing (20%), and decreasing (11%). Several key predictors including sex, age, injury severity, and education emerged as significant predictors of group membership in the persistent high , increasing , and decreasing depressive groups. However, variability in study methodologies and sample compositions posed challenges to direct comparison. Nonetheless, the review underscores the importance of long-term monitoring and the development of tailored interventions, as depression can manifest or intensify years post-injury. Understanding depressive symptom trajectories could help create personalised interventions, improving quality of life for those with depression after ABI.