Introduction: Several studies have been carried out regarding the possible overlap between Bipolar Disorder and borderline personality disorder. Up to now, it is not possible to provide a definitive picture. In fact, there is currently significant debate about the relationship between Borderline Personality Disorder and Bipolar Disorder.
Methods: MEDLINE searches were performed to identify the latest studies of these disorders, considering psychodynamic aspects.
Discussion: Bipolar disorder and borderline personality disorder share common clinical features, namely affective instability and impulsivity which however differ in quality. Consequently, to better understand these aspects, it is necessary to trace the stages of childhood psychological development.
Conclusions: It has been claimed that Bipolar Disorder Type II can be divided into two subtypes: one stable and functional between episodes and one unstable between episodes which is related to Borderline Personality Disorder. However, better diagnostic theories, psychiatrist's empathy and patience remain the essential tool to understand and to face human suffering.