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trouble, often the patient does not have an aware-ness that he or she is in trouble or annoys others. Hypomanic stateOn the other hand, in the hypomanic state of bipolar II disorder, the patient is energetic as if he or she has changed from the usual, becomes active in human relations, moves around without hesita-tion even after a short period of sleep, and looks clearly “high” to those around him or her compared to the usual. However, they do not cause trouble to the people around them as in a manic state.Depressive stateWhile the manic state is the most troubling symptom for the family, the depressive state is the most painful for the patient. The two core symp-toms of depression are “depressed mood,” which is a feeling of inexpressible annoyance that lasts all day, every day, and “loss of interest and pleasure,” which is a loss of interest in everything and the inability to feel happy or joyful in anything. The presence of at least one of these two symptoms is considered necessary for diagnosis.Including these two essential symptoms, depres-sion is defined as the daily occurrence of five or more of the various symptoms of depression for two weeks or more, such as sleep disturbance, decreased or increased appetite (and weight loss or gain), fatigue, psychomotor retardation (slowing down of movements), guilty feeling, loss of concen-tration, and suicidal thoughts.Clinical courseIn bipolar disorder, there is often an interval of about five years between the first episode (depres-sion or mania) and the next. During the remission state, when mania and depression have subsided, there are no symptoms, but if preventive therapy is not used, relapse will occur in most cases. If left untreated, the inter-episode interval gradually shortens over time1), and if the disease shifts to rapid cycling (four or more episodes per year), it becomes difficult to respond to pharmacotherapy.Comparing the duration of the manic state and depressive state, the duration of the depressive state is longer, and the patient is often unaware of the manic or hypomanic state, so many patients visit the clinic in a depressed state. However, in 18many cases, patients do not tell their doctors about their previous manic or hypomanic states at the time of their visit, in which case they are diagnosed with major depressive disorder and do not receive appropriate treatment.Bipolar disorder is a serious illness that can be life-threatening in its depressive state due to suicide and socially life-threatening in its manic state due to the consequences of its behavior. On the other hand, bipolar patients are also known to be at increased risk for cardiovascular disease, and cardiovascular disease is the leading cause of death in bipolar patients2).Worldwide, bipolar I disorder is considered to affect around 1% of the population, and 2-3% if both bipolar I and II are included1).On the other hand, in Japan, epidemiological studies large enough to estimate the prevalence have not been conducted, and the lifetime preva-lence of bipolar I and II patients combined is reported to be about 0.16 to 0.6%3-5), which is lower than in Europe and the United States. In the United States, the prevalence of bipolar disorder is lower in Asians compared with other ethnicities, suggesting that different genetic backgrounds may underlie this difference5).It is reported that 16% of patients who are being treated for the depressive state are bipolar disorder6), which is a higher percentage than the difference in lifetime prevalence (lifetime prevalence of depres-sion is about 15% worldwide and about 7% in Japan). This may be because, unlike depression, in which about a half of the patients experience only a single episode for a lifetime, bipolar disorder is characterized by multiple recurrent manic and depressive episodes.Bipolar disorder is classified into two categories based on the degree of mood elevation. The manic state is so severe that it interferes with family and work and requires hospitalization; On the other hand, the hypomanic state is a state of mood eleva-tion in which the person is clearly different from the person as usual but is not so severe to require hospitalization.Bipolar disorder with a manic state is called EpidemiologyDiagnosis