Marwaha, StevenAltaweel, Nada2025-02-122024https://hdl.handle.net/20.500.14154/74860Background: Major depressive disorder (MDD) is a common, debilitating, highly recurrent disorder representing a significant health concern and a leading cause of disability and mortality worldwide. Despite effective treatments, many depressed patients relapse, with around 50% to 80% likely to experience further episodes after achieving recovery. Personality has been proposed as an essential risk factor for recurrent depression. However, researchers have addressed limited personality traits and focused on personality disorders, leaving the role of many other personality traits in recurrent depression unclear. This thesis aimed to identify what personality traits contribute to the risk of recurrent depression in addition to other MDD outcomes (onset, persistence, recovery). Methods: Chapter two comprises a systematic review of personality traits as risk factors for relapse/recurrence in MDD. Chapter three includes a secondary data analysis that used prospective data from the Adults Psychiatric Morbidity Survey (APMS, 2000) to evaluate the association between borderline, obsessive-compulsive, and dependent personality traits and the change of depression status at 18 months (onset, persistence, and recovery). Chapter four presents a case-control study that examines the association between emotional dysregulation, affective lability, impulsivity, and recurrent depression. Results: The systematic review revealed that individuals with high neuroticism, borderline, obsessive-compulsive and dependent personality traits or disorders are more prone to the risk of recurrence compared to those without these traits. Additionally, the secondary data analysis study showed that borderline personality was the most robust factor; increased dependent personality traits were significantly associated with persistent MDD, and elevated traits of obsessive-compulsive personality were found to be related to the onset of MDD. The case-control study showed that emotional dysregulation and childhood maltreatment could work as risk factors for recurrent depression. Conclusion: These findings have important theoretical and practical implications, including efforts to develop targeted intervention plans tailored to patients’ characteristics. This thesis concludes by contextualising the findings within the existing literature, addressing their limitations, and proposing future directions. Overall, this thesis presents valuable insight into the role of personality traits in the risk of recurrent depression, highlighting their role in other important MDD outcomes and emphasising the need for further investigations in this area.187enDepressionRecurrent depressionRelapseRecurrencePersonality traitsEmotional dysregulationThesis