Bipolar disorder patients have significant brain volume changes compared with healthy individuals that are linked to age and duration of illness, but the changes do not appear to be diagnostically specific, say UK researchers.

Previous studies and meta-analyses of volumetric magnetic resonance imaging (MRI) in bipolar disorder and schizophrenia have revealed significant differences between affected individuals and healthy controls. However, there is substantial heterogeneity between the findings.

Danilo Arnone, from the University of Manchester, and colleagues therefore searched the Cochrane Library, EMBASE, PsychINFO, OVID and PubMED databases to identify volumetric MRI studies of brain regions comparing bipolar disorder patients with unrelated controls and schizophrenia patients. The team conducted a systematic review of the studies and a random-effects meta-analysis, while meta-regression was used to determine heterogeneity between the findings.

From 180 studies identified, 72 met the inclusion criteria. Of the included studies, 65 compared bipolar disorder patients and controls, with 18 of these also including patients with schizophrenia. Overall, the studies involved 1823 patients with bipolar disorder, 670 schizophrenia patients, 29 schizoaffective disorder patients, 106 unipolar depression patients, and 1940 healthy controls.

Bipolar disorder patients had, compared with healthy controls, a small but significant reduction in whole brain volume, at an effect size of -0.15, and significant increases in left and right lateral ventricles, at an effect size of 0.27. In both cases, there was no significant heterogeneity or publication bias.

It was also shown that bipolar disorder patients had significant increases in globus pallidus volumes versus controls, at an effect size of 0.57. However, there was significant heterogeneity and publication bias.

Compared with schizophrenia patients, bipolar disorder patients had significant increases in right amygdala volumes, at an effect size of 0.47, and bilateral reductions in the lateral ventricles, at effect sizes at the right and left ventricles of -0.35 and -0.26, respectively.

Heterogeneity was detected in a large number of nonsignificant brain volume changes. The effect sizes for specific volume changes compared with controls correlated with duration of illness, use of antipsychotic medication, age at onset, average age, year of publication, slice thickness, and use of mood stabilizers.

Age, percentage of male participants, and euthymia were also associated with specific volume changes in comparison with schizophrenia patients, the team reports in the British Journal of Psychiatry.

The team writes: “We found that bipolar disorder is associated with global and prefrontal volumetric brain reductions, enlarged lateral ventricles and an enlarged globus pallidus.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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