Bipolar disorder (manic depression) is a chronic illness that repeats depression and manic states.In Japan, it is said that about 0.7% of people, including type I, who has a severe manic state, and type II, who has a mild manic state, develop the disease.Manic state becomes abnormally "high" and takes actions that are unthinkable in common sense, causing social loss and troubles in relationships.Furthermore, when they turn into depression, they tend to blame themselves violently and take self-destructive behavior.Therefore, it is known that the rate of suicide is higher than that of depression, and the recurrence rate is also high.At present, the cause has not been clarified, and the main treatment is symptomatic treatment with drugs that stabilize the mood.

　In this study, we analyzed the metabolism of cerebrospinal fluid in patients of the same age and healthy subjects to investigate the cause.As a result, we found that the concentration of a substance called isocitric acid in the patient's cerebrospinal fluid was significantly high.Further analysis of the brains of deceased patients revealed that the gene for the enzyme that breaks down isocitric acid is poorly functioning.This suggests that the metabolic function of citric acid in the intracellular mitochondria may be abnormal.This is a result that is consistent with the mitochondrial abnormality hypothesis that has been proposed so far as the cause of bipolar disorder.

　This allowed us to broadly narrow down where the abnormality occurred in bipolar disorder.However, in order to lead to a new treatment method, it is necessary to investigate the onset mechanism in more detail, such as identifying the abnormal part of the gene involved in the metabolism of citric acid.It is expected that future research will further investigate the cause.