Increased levels of a mitochondrial DNA deletion in the brain of patients with bipolar disorder

Mutations in mitochondrial DNA (mtDNA) have been implicated in the pathophysiology of affective disorders. To examine possible pathophysiological significance of mtDNA deletions in bipolar disorder, the concentration of the 4977-base-pair deletion in mtDNA in the autopsied brains of 7 patients with bipolar disorder, 9 suicide victims, and 9 controls was examined using a quantitative polymerase chain reaction method. The ratio of deleted to wild-type mtDNA in cerebral cortex was significantly higher in patients with bipolar disorder [0.23 ± 0.18 (mean ± SD)%] compared with that in age-matched controls (0.06 ± 0.07%, p < 0.05). This result supports a hypothesis that mtDNA deletions may play a role in the pathophysiology of bipolar disorder.