Special Issue on Bipolar Disorder

The past two decades have seen a burgeoning of interest in Bipolar Disorder. This has been marked by a wealth of new research evidence but also by an increasing understanding of the significant impact that this illness has, not only for sufferers and their carers, but also for society. Bipolar Disorder is common. Bipolar Type I and Type II sub-types have a lifetime prevalence of between 1% and 2% and the Bipolar spectrum, a category about which much remains unknown, is found in up to an additional 5%. The World Health Organization has estimated that Bipolar Disorder is the 6th leading cause of disability worldwide among young adults (Murray & Lopez, 1997) underlining that Bipolar Disorder is a serious public health concern. Many patients make a relatively good symptomatic recovery from Bipolar Disorder but functional recovery lags well behind that. A recent pan European study revealed that two thirds of Bipolar patients have a moderate or poor outcome and employment rates in Bipolar Disorder are disappointingly low, particularly when the predicted trajectory of employment for many patients is taken into consideration (Goetz et al., 2007).

Despite the large burden of Bipolar Disorder on patients, carers and society, research on Bipolar Disorder was relatively limited until about 10–15 years ago. In 2003, Clement and colleagues published a paper showing that the number of publications, grants and clinical trials in Bipolar Disorder up to the year 2000 was about a third of that of schizophrenia (Clement, Singh, & Burns, 2003). However, this situation has changed dramatically in the last decade and major advances are being made in the understanding of the disorder and its natural history and in the elucidation of its aetiopathogenesis and neurobiology. There has also been a large increase in the number of clinical trials and an improving evidence base for treatment. At the end of this decade it is timely that this special issue of the Journal of Mental Health is published and it includes four papers reviewing selected areas of exciting new research in Bipolar Disorder which illustrate the progress made.

Bipolar Disorder has been a relative latecomer to the studies which utilize developments in neuroimaging. The paper by Cousins and Palaniyappan summarizes some of the new data in this field with a particular focus on the issue that Bipolar Disorder may be a disorder of network connectivity. There has been a considerable interest in studies which have shown that Bipolar patients, even when euthymic, have neurocognitive abnormalities, particularly in executive function tasks which link to the frontal cortex. However, studies have shown that there is no major loss of grey matter in the cortex in Bipolar Disorder in the same way as this is found in schizophrenia (Kempton et al., 2008). However, several lines of evidence point to changes in white matter in Bipolar Disorder and this paper reviews the up-to-date evidence in this field. This very strong lead will provide a focus and a potential biomarker in future studies looking at the aetiopathogenesis of Bipolar Disorder, particularly in genetic and developmental studies.

There have been a lot of studies on the treatment of Bipolar Disorder over the last decade which has been very welcome. The positive effect of certain medications in Bipolar Disorder may also provide an important clue to help understand the disorder. Two papers in this special issue tackle this issue. Firstly, lithium remains the gold standard particularly for the prevention of manic episodes particularly in patients with Bipolar Type I Disorder. Smith and colleagues review the data on predictors of outcome from use of lithium and detail studies which have investigated whether various candidate polymorphisms are linked to lithium responsivity. This exciting research may well provide us with important clues to help us to tailor treatment to individual patients but also help us to understand the disorder in more detail and aid the development of new medications, perhaps with better side effect profiles. A further lead is that some but not all anti-convulsants are effective in Bipolar Disorder. Grunze reviews this topic and looks into the question of whether or not the mechanism of action underlying the anticonvulsants efficacy profile differs and whether it can help us understand this differential efficacy. Again such research should lead to the development of improved treatments in the near future.

Finally, Berk and colleagues review the issue of service delivery for Bipolar Disorder and particularly the notion of early intervention. There is no doubt this disorder's large morbidity is partly due to the consequences of the disorder and the evidence is increasing that early intervention and prevention of consequences is the way forward. The group in Melbourne are very well placed to review this topic since they have done very active research on this theme. It is very important to recognize that, whilst changes in understanding of the disorder and its neurobiology and its treatment are vital, it is also important that those treatments are delivered in the appropriate setting for this disorder with its very specific clinical and social problems. The paper argues that the development of a staging model would assist in the development of treatment tailored to the stage of illness and discusses the need to develop treatments and services appropriate to patients early in their illness. Some of the obstacles that need to be overcome, such as diagnostic dilemmas and the problem of patients'acceptance of the illness at an early stage, are also usefully outlined.

The contents of this special issue are inevitably selective and there are developments in other fields and in other methodologies which are as important but which cannot be reviewed here for the sake of space. However, we hope that putting these papers reviewing cutting edge issues in Bipolar Disorder together will help to stimulate the field further.