In an article published in this month’s Biological Psychiatry entitled “Structural Magnetic Resonance Imaging in Bipolar Disorder: An International Collaborative Mega-Analysis of Individual Adult Patient Data” (Hallahan et al.), researchers pulled together a large number of magnetic resonance imaging studies to compare the brains of people with bipolar disorder to those of healthy control subjects. Their goal was to make sense of some of the conflicting data that had come out of the studies individually.
Using so many studies, from research groups all over the world, the authors are able to examine all of the results together and come up with some more comprehensive findings. This is called a “meta- analysis.” “Mega-analysis” is an informal term that describes a huge meta-analysis.
The findings point to several brain areas that are larger in patients with bipolar disorder – the right lateral ventricle, the left temporal lobe, and the right putamen – regions strongly connected with emotional regulation and processing.
There was also suggestion of overall decreased cerebral (brain) volume in people with bipolar disorder, and longer duration of illness was associated with more reductions in brain volume. Patients with bipolar disorder also showed decreased volume of the hippocampus – a brain region that is very important in mood and emotions.
A striking result of this meta-analysis was that people treated with lithium were found to have increased volume of the hippocampus as compared to people with bipolar who were not treated with lithium, as well as compared to healthy control subjects. Lithium treatment was also associated with increased volume of the amygdale – another brain region that plays key roles in anxiety and mood reactions.
So in addition to more definitively describing the brain areas that are altered in people with bipolar disorder, the study suggests that Lithium treatment might actually correct some of the underlying brain changes that are associated with bipolar disorder. These are remarkable steps in the journey toward more fully identifying the biology of bipolar disorder, helping us understand why certain treatments may be effective, and helping us develop more specific and effective treatments in the future.
Photo by Marieke Kuijjer, available under a Creative Commons attribution license.