Idiopathic hypersomnia (IH) is a sleep disorder in which a person is excessively sleepy (hypersomnia) during the day and has great difficulty being awakened from sleep. Idiopathic means there is not a clear cause.

Hypersomnia - idiopathic; Drowsiness - idiopathic; Somnolence - idiopathic

IH is similar to narcolepsy in that you are extremely sleepy. It is different from narcolepsy because IH doesn't usually involve suddenly falling asleep (sleep attacks) or losing muscle control due to strong emotions (cataplexy). Also, unlike narcolepsy, naps in IH are usually not refreshing.

Symptoms often develop slowly during the teens or young adulthood. They include:

• Daytime naps that do not relieve drowsiness
• Difficulty waking from a long sleep -- may feel confused or disoriented (''sleep drunkenness'')
• Increased need for sleep during the day -- even while at work, or during a meal or conversation
• Increased sleep time -- up to 14 to 18 hours a day

Other symptoms may include:

• Anxiety
• Feeling irritated
• Loss of appetite
• Low energy
• Restlessness
• Slow thinking or speech
• Trouble remembering

Your health care provider will ask about your sleep history. The usual approach is to consider other possible causes of excessive daytime sleepiness.

Other sleep disorders that may cause daytime sleepiness include:

• Narcolepsy
• Obstructive sleep apnea
• Restless leg syndrome

Other causes of excessive sleepiness include:

• Depression
• Certain medicines
• Drug and alcohol use
• Low thyroid function
• Previous head injury

Tests that may be ordered include:

• Multiple-sleep latency test (a test to see how long it takes you to fall asleep during a daytime nap)
• Sleep study (polysomnography, to identify other sleep disorders)

A mental health evaluation for depression may also be done.

Your provider will likely prescribe stimulant medicines such as amphetamine, methylphenidate, or modafinil. These medicines may not work as well for this condition as they do for narcolepsy.

Other medicines for idiopathic hypersomnia, which are also commonly used for narcolepsy, include sodium oxybate (or oxybate salts) and newer wake-promoting agents such as pitolisant and solriamfetol.

Lifestyle changes that can help ease symptoms and prevent injury include:

• Avoid alcohol and medicines that can make the condition worse
• Avoid operating motor vehicles or using dangerous equipment
• Avoid working at night or social activities that delay your bedtime

Discuss your condition with your provider if you have repeated episodes of daytime sleepiness. They may be due to a medical problem that needs further testing.

Avidan AY. Sleep and its disorders. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 101.

Dauvilliers Y, Bassetti CLA. Idiopathic hypersomnia. In: Kryger M, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 113.

Nallu S, Benbadis SR. Disorders of sleep. In: Wing EJ, Schiffman FJ, eds. Cecil Essentials of Medicine. 10th ed. Philadelphia, PA: Elsevier; 2022:chap 108.