is needed; then, medication substitution can be undertaken. Mood disorders, like depression, anxiety disorder and bipolar disorder, can also be associated with hypersomnia. The complaint of excessive daytime sleepiness in these conditions is often associated with poor sleep at night. "In that sense, insomnia and EDS are frequently associated, especially in cases of depression." Hypersomnia in mood disorders seems to be primarily related to "lack of interest and decreased energy inherent in the depressed condition rather than an increase in sleep or REM sleep propensity". In all cases with these mood disorders, the MSLT is normal (not too short and no SOREMPs). Posttraumatic hypersomnias In some cases, hypersomnia can be caused by a brain injury. Researchers found that the level of sleepiness is correlated with the severity of the injury. Even if patients reported an improvement, sleepiness remained present for a year in about a quarter of patients with traumatic brain injury. Recurrent hypersomnias Recurrent hypersomnias are defined by several episodes of hypersomnia persisting from a few days to weeks. These episodes can occur weeks or months apart from each other. There are 2 subtypes of recurrent hypersomnias: Kleine-Levin syndrome and menstrual-related hypersomnia. Kleine-Levin syndrome is characterized by the association of episodes of hypersomnias with behavioral, cognitive and mood abnormalities. The behavioral disturbances can be composed of hyperphagia, irritability, or sexual disinhibition. The cognitive disorders consist of confusion, hallucinations or delusions. Mood symptoms are characterized by anxiety or depression. Menstrual-related hypersomnia is characterized by episodes of excessive sleepiness associated with the menstrual cycle. Researchers found that the degree of premenstrual symptoms were correlated with daytime sleepiness. Unlike Kleine-Levin syndrome, hyperphagia and hypersexuality are not reported in people with menstrual-related hypersomnia, but hypophagia could be present. Ordinarily, these episodes appear 2 weeks before menstruation. A few studies have attested that some hormones as prolactin and progesterone could be responsible for Menstrual-Related Hypersomnia. Therefore, different contraceptive pills could improve the symptoms. The sleep architecture changes. There is a decrease of slow-wave sleep and an increase of slow-Theta-wave activity. Assessment tools Polysomnography Polysomnography is an objective sleep assessment method. It comprises a lot of electrodes which measure physiological variables related to sleep. Polysomnography often includes electroencephalography, electromyography, electrocardiography, muscle activity and respiratory function. Polysomnography is helpful to identify the very short sleep onset latency period, the very efficient sleep (more than 90%), the increased slow wave sleep, and sometimes an elevated amount of