This is, we believe, the first monograph focusing on Bipolar II Disorder by itself. ‘By itself’ raising an obvious question. If Bipolar II is a true mood disorder, is distinctly more common than Bipolar I (or manic depressive illness) but has comparable disability, sequelae and suicide rates, why has it not invited any previous definitive overview? The answer will be quickly apparent to readers.

Firstly, Bipolar II is a relatively ‘new’ condition, in the sense of it being defined and detailed only over the last few decades. Secondly, its status as a ‘condition’ is challenged by many. Thirdly, its detection by professionals is low and delayed. Fourthly, it is commonly viewed as a mild condition (e.g. ‘bipolar lite’), and as therefore of little consequence in terms of its differentiation from unipolar depression. Fifthly, there are no treatment guidelines for its management, with clinical management – if conceding such a diagnosis – generally extrapolating strategies from the management of Bipolar I Disorder.

Most psychiatric monographs are written when there is a bank of knowledge. Not on this occasion. Here, author after author, all with expertise in the bipolar disorders, note the lack of a clear knowledge base and of any formalised clinical guidelines. This book was designed, however, to detail both what is currently known or debated, and what needs to be clarified.