It is a difficult task to comment upon an individual's clinical model for treating ‘Bipolar II Disorder’ (BP II) without clarity about the criteria being used to make that diagnosis. In contemporary academic and clinical practice there is a myriad of definitions for BP II, each with associated stated and unstated connotations. There is a consequent unfortunate conflation in the use of this term, with the implicit message that ‘all Bipolar II Disorder is the same’. This is in fact not true, as a quick reflection on the historical origins of the use of this term would indicate. The term ‘Bipolar II Disorder’ was originally coined by Fieve and Dunner (1975) to describe an attenuated form of classical bipolar disorder/manic depressive illness in which the elevated component of the illness was less severe than in Bipolar I Disorder (BP I). This concept of BP II, which became enshrined in the RDC and DSM nosological systems, and incorporates minimum durations of hypomania varying from 2 to 7 days, has been validated by being demonstrated to be genetically related to BP I.

A more recent usage has stemmed from the broad concept of the ‘soft bipolar spectrum’ (Akiskal and Mallya, 1987), in which conceptualisation of BP II has been extended to include brief hypomanic episodes as well as cyclothymic and hyperthymic personality traits (Akiskal et al., 2000).