Complaints of hypersomnia in mood disorders are more common in women than men, younger people than older people, and those with bipolar rather than unipolar depression. Hypersomnia symptoms such as prolonged nighttime sleep and daytime sleepiness have been shown to be risk factors for recurrence and relapse of depressive episodes and are considered to be clinically important symptoms. Even if patients complain of hypersomnia, objective findings on prolonged nighttime sleep and excessive daytime sleepiness are identified by polysomnography and multiple sleep latency tests only in some patients, suggesting that hypersomnia in mood disorders can be pathologically different from central hypersomnia, such as narcolepsy. In a depressed state, prolonged time in bed due to fatigue, decreased motivation, and lying in bed as an avoidance behavior may also be regarded as hypersomnia symptoms.
 When physicians hear complaints of hypersomnia, they should first exclude the sedative effect of the drugs that patients are taking. It is also necessary to exclude excessive daytime sleepiness due to insomnia and other sleep disorders, such as obstructive sleep apnea, restless legs syndrome, and periodic limb movement disorder. A recent study demonstrated that the hypersomnia symptoms of long sleep and excessive sleepiness are independent and not correlated. Therefore, it is also important to distinguish them in order to appropriately manage them.
 As for treatment of hypersomnia symptoms in mood disorders, there are a few methods that have been shown to be effective for some subtypes and related diseases. In seasonal affective disorder, bright light therapy has been reported to be effective not only for depressive symptoms but also for hypersomnia. Low-dose aripiprazole, which has come to be used for delayed sleep phase disorder, may be effective for hypersomnia symptoms in mood disorders, but this has not yet been verified. Bupropion, which has an inhibitory effect on noradrenaline and dopamine reuptake, was reported to be more effective than selective serotonin reuptake inhibitors for hypersomnia in depression. In the present paper, the author reviewed the literature regarding hypersomnia in mood disorders, and described the current approach to its management as well as the author's proposed approach.
 Author's abstract