Voxel-based morphometric analysis on the volume of gray matter in bipolar I disorder

A number of previous studies have found that bipolar disorder is associated with abnormalities of brain structure. In this study we used optimized voxel-based morphometry (VBM) to compare gray matter volume between patients with bipolar I disorder and healthy controls. Twenty-four bipolar I patients (15 males and nine females) and 36 healthy controls (21 males and 15 females), who were well matched for age and gender, were scanned using structural magnetic resonance imaging. Gray matter volume was assessed and compared using optimized VBM, and the correlation between duration of illness/number of episodes and regional volumes was analyzed. There was no difference in whole-brain gray matter volume between the two groups. Optimized vVBM showed that subjects with bipolar I disorder had smaller volumes in the left inferior parietal lobule, right superior temporal gyrus, right middle frontal gyrus and left caudate. Only the volume of the right middle frontal gyrus was correlated with duration of illness and number of episodes in patients. These results suggest widespread gray matter defects in bipolar I disorder, which may play an important role in onset of the illness.