Table 1 Advantages of merging bipolar I and II disorder vs. maintaining distinction

Advantages of merging

1. Conforms to clinical dimensional reality. Truer reflection of clinical picture of illness

2. Promotes greater consistency in treatment approaches

3. Encourages more coherence in bipolar spectrum thinking and research—accommodates mixed states and allows for differential clinical expression of bipolar disorder

Advantages of maintaining distinction

1. Consistent with lack of evidence to support change

2. Less disruptive to patients and families

3. Acknowledges differences in clinical characteristics

 a. Dominance of depression in bipolar II disorder

 b. Differential susceptibility to switching

 c. Greater functional impairment in bipolar I disorder due to destructive nature of manic states