Hypersomnia is present in up to 5% of the population at some point in their lives and is more prevalent in males. Causes can vary greatly but often the symptoms begin prior to age 30 and continue to progress unless treated. Some research suggests that sleep disruptions during the night (such as breathing related sleep disorder) causes the individual to lack REM sleep and therefore feel tired despite the fact that he or she has slept through the night.
The criteria for primary hypersomnia include excessive sleepiness for at least one month as evidences by prolonged sleep during the night or excessive daytime sleep. This must cause significant distress or impairment for the individual and can not occur exclusively during another mental illness, medical condition, or substance use.
Treatment can include medication, exercise, changes in diet or other techniques employed to treat associated disorders if present (e.g., breathing related sleep disorder). If associated with another mental (e.g., depression) or medical condition the symptoms of primary hypersomnia will often dissipate went the other condition improves.
Hypersomnia can be chronic, especially when not associated with another disorder and therefore can continue to worsen if left untreated. Treatments are readily available and can improve the prognosis significantly.