People suffering from hypersomnia find it difficult to stay awake during the day due to a compromise in the alertness system. There are primary and secondary causes of hypersomnia.

Secondary hypersomnia means that there is an identifiable reason behind the sleepiness. Sometimes. it’s an easily identifiable cause – like just not allowing for enough sleep at night. Other times, sleep is disrupted by specific behavioral causes (such as nicotine and alcohol usage in the evenings) or by sleep disorders (e.g. sleep apnea). In contrast, primary hypersomnia are disorders that are not due to other easily identifiable causes. Examples include narcolepsy, idiopathic hypersomnia, and Kleine Levin syndrome.


Sleep and wake states are mediated by chemicals in your brain called neurotransmitters. One of the main regulators of these neurotransmitters includes a protein called orexin (AKA hypocretin). Orexin allows certain neurotransmitters to be dominant during the day (allowing for wakefulness and alertness) while others predominate during sleep to allow for continuous cycling between different sleep stages.

Narcolepsy is a condition with an absence or relative lack of orexin, which occurs at birth or shortly thereafter. In some cases of trauma (e.g. subarachnoid hemorrhage), narcolepsy can also manifest. The relative absence of orexin results in dysregulation of the sleep and wake neurotransmitters, manifesting as both an inability to stay awake as well as difficulty staying asleep. When sleep is disrupted, sleep intrudes into wakefulness, which can manifest as a variety of symptoms including:

  • Sleepiness during the day.
  • Cataplexy, which is transient muscle weakness (e.g. eye closure, slack jaw, weak knees) triggered by a strong emotion such as laughter, anger, and surprise.
  • Hypnogogic or hypnopompic hallucinations, which are dream imagery (e.g. figures in the doorway, things crawling across the floor, voices in the next room) that occur upon falling asleep or waking up from sleep.
  • Sleep paralysis, which is the relative inability to move, similar to being in a sleep state, even if you are wide awake.

Idiopathic Hypersomnia

Idiopathic hypersomnia (IH) is thought to occur either because the excitatory (wake system) is less sensitive or because the inhibitory system is hypersensitive. Clinically, there is an overwhelming sense of sleepiness, which – unlike narcolepsy – is not quite refreshing and persists regardless of how much sleep is involved. People with IH often report the same amount of wakefulness and alertness regardless of the amount of sleep, whether it is 8 hours of 12 hours.

Cyclic Hypersomnia

Cyclic hypersomnia syndromes (e.g. Kleine Levin syndrome) are episodes of extreme sleepiness that appear sporadically. These self-limited episodes include massive amounts of sleep, interspersed only by using the restroom or eating episodes. Eating episodes are frequently altered and may include inappropriate foods that are not normally eaten (e.g. large amounts of carbohydrates, flour, butter). Mood during these brief wake periods can be altered, including inappropriate language and behaviors (e.g. cursing) and moodiness. Duration of episodes typically consists of a few days after which either relative insomnia occurs or normal sleep-wake pattern resumes. The cycling between hypersomnia-insomnia mimics a “bipolar” pattern, even if a mood disorder is not apparent.


Medical evaluation will likely consist of a review of your symptoms, physical examination, blood tests to evaluate for underlying medical issues (e.g. anemia or thyroid issues), and potentially sleep studies. For primary hypersomnia, testing consists of a polysomnography study which is an overnight sleep study in a laboratory, monitored by a technician. The polysomnography study (or PSG) involves placement of electrodes on the scalp to monitor brain waves and sleep stages, face to measure eye movements, neck for airflow and snoring, belts on the chest and belly to monitor breathing, a heart monitor, oxygen monitor over the finger, and leg monitors to monitor movement. Following this overnight study, a next-day napping test (called a Multiple Sleep Latency Test, or MSLT) will commence. The MSLT consists of 5-nap sessions, which occur every 2 hours, to measure how quickly you fall asleep. In between naps, activities are not limited except for lack of caffeine. The naps are assessed for the average time to fall asleep and whether the dream stage of sleep (called REM sleep) occurs during the nap.

Do I have a hypersomnia disorder?

It is important to talk to a sleep doctor who can properly diagnose the cause of your hypersomnia and implement the most effective treatment. If you have symptoms of sleepiness, talk to your doctor!

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