White matter integrity affects functional outcome in bipolar disorder
MedWire News: The functional outcome of patients with bipolar disorder is influenced by cognitive performance, clinical course, and white matter volume, research shows.
The study, published in the Journal of Affective Disorders, is the first to report an association between white matter integrity and functional outcome.
"A frequent criticism of research into functional outcomes in psychiatry is that it offers little or no information with regards to biological mechanisms. The present results provide a direct link… and extends the argument for the importance of white matter integrity for the pathophysiology of the disorder," Sophia Frangou (King's College London) and colleagues report.
Almost two thirds of bipolar disorder patients show moderate to severe functional impairment; approximately 50% are either unemployed or have reduced occupational roles. Additionally, up to a third never marry and between 20 and 60% live with the support of family members.
Both clinical factors such as depression and cognitive impairment in various domains have been found to influence functional outcome - but together account for no more than 40% of the variance in outcomes, according to prior research.
"These findings underscore the need to expand the search for outcome predictors and consider candidates within the wider phenotypic spectrum of bipolar disorder," Frangou et al comment.
The researchers therefore assessed the relationship between functional status and key clinical, cognitive, and brain structural parameters in 41 euthymic bipolar disorder patients and 50 of their unaffected first-degree relatives.
Psychosocial function was evaluated using the General Assessment of Functioning (GAF) scale.
Multiple regression analyses revealed that IQ, total white matter volume, and a predominantly depressive illness course were independently associated with functional outcome in bipolar disorder patients, but not in their relatives, and accounted for a substantial proportion (53%) of the variance in patients' GAF scores.
There were no significant domain-specific associations between cognition and outcome after consideration of IQ. This is in keeping with a general shift in the field from multiple cognitive domains to composite or global measures that appear to better capture the cognitive profile of patients, say Frangou et al.
"Our results argue that white matter integrity is pertinent to outcome across a broad range of disease severity and suggest that preservation of white matter integrity may prove an important therapeutic target in its own right," they comment.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010
By Andrew Czyzewski