This overview of bipolar disorder offers six scholarly reviews of the condition, accompanied by 122 brief commentaries from international experts. The result is a stimulating and comprehensive account of recent research, set in the context of a consensus about the findings. The commentaries include many enlightening and imaginative ideas.

Akiskal's introductory review, on the diagnosis and classification of bipolar disorders, is perhaps his most articulate and convincing exposition of the concept of the ‘bipolar spectrum’ of conditions. These he subdivides into eight types, that can be recognised in up to 50% of the population. The commentaries show broad appreciation of the spectrum concept, but express the need for strict criteria to identify homogeneous groups for study. Only then can the supposed pharmacological ‘dissections’ be achieved, identifying patients who may benefit from particular therapeutic approaches.

Bowden reviews drug treatments. The different perspective of North American and European experts is intriguing. For example, in the USA there is reluctance to use antidepressants for bipolar depression for fear of inducing mania, even though authorities such as Jules Angst argue that such switches are an inevitable sequel to effective resolution of depression in these people. One commentator actually recommends two failed trials with ‘mood stabilisers’ before giving an antidepressant. Yet, the definition of a mood stabiliser is not clear and no anticonvulsant drug has unequivocal evidence for prophylactic efficacy against mania.

Several reasons suggest themselves for the divergence of expert opinion in the USA from opinion elsewhere and from clinical practice. In the USA there may be greater admiration for new approaches and more-intense fear of lawyers (and therefore of side-effects) than in Europe. Boland & Keller suggest that third-party reimbursement plays a part in diagnosis and treatment: ‘it is difficult to find a patient with any sort of chronic psychiatric illness who is not on a mood stabiliser’. Kasper suggests that North American opinion leaders ‘base their sound clinical knowledge on patient samples largely consisting of rapid-cyclers’, an uncommon sub-type of bipolar disorder in Europe. A further possibility is that American academics are disinclined to refer to journals published outside the USA. Yet American investigators have been at the forefront of developments in clinical trials of new drugs.

Other reviews deal with psychological therapies, the presentation in youth and old age, and the economic implications of the disorder. The recent expansion of knowledge means that there is a greater need for specialisation in the provision of health care to patients with bipolar disorder, who have been neglected in official plans such as the National Service Framework.