Assessing Risk and Resilience for Bipolar Disorder

by Sandra A. Swanson

September, 2009

London researchers have gained insight into changes in brain structure that correspond with bipolar disorder and why some close relatives of patients with the disorder do not develop it.

In a study published Sept. 2 in the Journal of Neuroscience, the investigators examined magnetic resonance imaging scans from 30 patients with bipolar disorder and 50 of their close relatives (either offspring or siblings), as well as a control group of 50 nonrelatives who did not have the disorder. They found that people with a genetic risk for the disorder (irrespective of whether they had it) had greater volume in the left insula, a region responsible for physical sensations that stem from emotions, as when “butterflies in the stomach” result from nervousness.

“Although [it is] interesting, this finding does not tell us who will stay well or who will develop a mood disorder,” says lead researcher Sophia Frangou of the Institute of Psychiatry at King’s College London.

Other findings did show a correlation between specific brain structures and the development of bipolar disorder, however. Analysis of the scans revealed that the volume of the substantia nigra was greater in bipolar patients. Located in the midbrain, this region links emotion with movement.

“Its involvement in bipolar disorder … is probably connected to the overactivity patients show during periods of mania,” Frangou says.

The researchers also found brain-structure similarities in relatives who lacked any psychiatric symptoms. In those subjects, the left cerebellum was enlarged. “It seems that [a larger cerebellum] helps balance emotional reactions and may therefore contribute to resilience to mood disorders,” says Frangou.

The researchers plan to examine the effect bipolar-disorder risk genes have on cognition and on brain structure and function. In an effort to identify high-risk patients, they are also collaborating with colleagues who specialize in bioinformatics, says Frangou: “We are working together to implement more sophisticated statistical methods for using biological data, such as the results of this study, to develop diagnostic tests.”