Personal recollections about the development of Bipolar II disorder

Background: This paper reviews the development of Bipolar II disorder, defining the development of diagnosis and the current state of the art in treatment. Methods: Through his training and working in psychiatry, the author recounted the early days when Bipolar II disorder was conceptualized and developed as a separate clinical entity at the Department of Psychiatry at Washington University, US National Institute of Mental Health, and New York State Psychiatric Institute/Columbia University. The author also participated in the process leading to the inclusion of Bipolar II in the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition (DSM-IV) in 1994. In this review, the author presents his recollections how bipolar II disorder came about and entered the diagnostic criteria that we now use in psychiatry. Results: The diagnostic criteria of Bipolar II disorder in DSM-IV and DSM-5 were reviewed. Then, the author stressed the importance of differentiating Bipolar II disorder clinically, how to make the diagnosis of Bipolar II disorder, differentiating mania from hypomania, differentiating hypomania from unipolar depression (i.e., major depressive disorder), and provided useful clinical tips related to ascertaining this diagnosis. Then, he reviewed and raised some issues in treating Bipolar II disorder. The neuroscience-based nomenclatures were given for all drugs used in treating Bipolar II disorder in this review. Conclusion: Bipolar II disorder has come a long way to be accepted as a valid clinical entity. The author believes that more clinical knowledge can further improve the diagnosis and treatment for patients with Bipolar II disorder.