This condition is similar to narcolepsy in that you are extremely sleepy. It is different from narcolepsy because idiopathic hypersomnia does not usually involve suddenly falling asleep (sleep attacks) or losing muscle control due to strong emotions (cataplexy). Also, unlike narcolepsy, naps in idiopathic hypersomnia 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

The health care provider will ask about your sleep history. The usual approach is to consider other potential 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, and modafinil. These drugs may not work as well for this condition as they do for narcolepsy.

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

Hypersomnia – idiopathic; Drowsiness – idiopathic; Somnolence – idiopathic

Bassetti CL, Dauvilliers Y. Idiopathic hypersomnia. In: Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 5th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 86.

Masri TJ, Gonzales CG, Kushida CA. Idiopathic hypersomnia. Sleep Med Clin. 2012;7:283-289.

Updated by: Allen J. Blaivas, DO, Division of Pulmonary, Critical Care, and Sleep Medicine, VA New Jersey Health Care System, Clinical Assistant Professor, Rutger’s New Jersey Medical School, East Orange, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.