Broad personality change occurs in 68.1% of patients with traumatic brain injuryMost Patients With Brain Injuries Experience Lasting Personality Changes

Background: Personality change is a debilitating consequence of traumatic brain injury (TBI), yet its prevalence, characteristics, and treatment remain poorly understood. Methods: We completed a pre-registered (CRD42023440990) systematic review and meta-analysis searching four databases (MEDLINE, PsycINFO, EMBASE and CINAHL) for primary studies assessing personality change after TBI. We synthesised conceptualisation, prevalence, longitudinal outcome, lesion location and treatment. Prevalence was estimated using a random effect meta-analysis using the Paule-Mandel estimator, with subgroup, meta-regression and robustness analyses. Results: 101 studies were included in this review, seventeen of which were suitable for meta-analysis. Personality change was defined inconsistently although common symptoms involved the emergence or increase of affective, behavioural, and social disturbances, including irritability, depression, emotional instability, anger outbursts, social withdrawal, anxiety, impulsivity, restlessness, aberrant motor behaviours, and aggression. The prevalence of secondary personality disorder was estimated as 29.1% (CIs 22.5% - 36.2%) and prevalence of broad personality change was 68.1% (CIs 53.4% - 81.2%). Robustness analyses showed that the estimate for broad personality change should be treated with caution as it was unstable when adjusted for risk of bias and potential publication bias. Follow-up studies, although of varying quality, consistently showed personality change remained stable over long follow-up periods. The relationship between personality change and specific lesion locations in TBI remains unclear, likely due to the poor methodological quality of studies examining this association. Perhaps most concerning, there is limited evidence and very few systematic studies addressing treatment. Conclusion: Personality change is a common and persistent consequence of TBI. Varying definitions, and the lack of high-quality lesion mapping studies and systematic investigations into treatment highlights critical gaps in understanding and management.