Borderline personality disorder (BPD) is defined within psychiatry and related psychological fields as a disorder characterized primarily by emotional dysregulation, extreme "black and white" thinking, or "splitting" (believing that something is one of only two possible things, and ignoring any possible "in-betweens"), and turbulent relationships. It can also be described by mental health professionals as a serious mental illness characterized by pervasive instability in mood, interpersonal relationships, self-image, identity, and behavior, and a disturbance in the individual's sense of self.
The disturbances suffered by those with borderline personality disorder have a wide-ranging and pervasive negative impact on many or all of the psychosocial facets of life -- including employability and relationships in work, home and social settings. Furthermore, BPDs may be marginalized by society due to their moods and behaviors.