This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To assess the beneficial and harmful effects of psychological therapies for people with borderline personality disorder (BPD). B A C K G R O U N D Description of the condition Borderline personality disorder (BPD) is a condition first recognised in the 20th century (Gunderson 2009). Historically, the term BPD was coined by Adolph Stern to describe a condition in the 'borderland' between psychosis and neurosis (Stern 1938). Subsequent psychoanalytic contributions (especially that of Kernberg 1975) have reaffirmed this distinction, emphasising that the capacity to test reality remains grossly intact but is subject to subtle distortions, especially under stress. According to current diagnostic criteria, BPD is characterised by a pervasive pattern of instability in affect regulation, impulse control , interpersonal relationships, and self-image (APA 2013; WHO 1993). Clinical hallmarks include emotional dysregulation, impulsive aggression, repeated self-injury, and chronic suicidal tendencies (Fonagy 2009; Lieb 2004). Whereas some authors have suggested that it is a variant of affective disorders (Akiskal 2004), others claim that it is only the causes of these diseases that partially overlap in BPD (Paris 2007). Despite the difficulties in defining and delimiting the condition, BPD is still being widely researched. Its importance stems from the considerable psychological suffering of the persons concerned (