The main symptom of Idiopathic Hypersomnia (IH) is excessive deep sleep. Despite adequate and often extraordinary amounts of good quality sleep (eg: 11 hours or more per night) people with IH still feel excessively sleepy during the day. Other symptoms typically include:


  • Chronic excessive daytime sleepiness often resulting in long daytime naps.

  • Long and unrefreshing naps. Naps are usually more than one hour long and are typically not refreshing.


  • Extreme and prolonged difficulty awakening from sleep, accompanied by confusion, disorientation, irritability and poor coordination with an uncontrollable desire to go back to sleep. It can also include automatic behaviour
    ie: performing tasks without consciously knowing it and not remembering you have done them eg: turning off alarm clocks or
    answering your phone. This is known as “sleep drunkenness”.


  • Cognitive dysfunction (commonly referred to as 'brain fog'): problems with memory, automatic behaviour, concentration and attention.

Unlike in other sleep disorders, the sleep in patients with Idiopathic Hypersomnia is normal; there are no disturbances that can account for these symptoms.

Click here to view and download our Idiopathic Hypersomnia Factsheet*. If you are a medical professional and would like free copies of our (trifold) IH information Brochure* for your practice please contact us.

Our Factsheet/Brochure was written by HA's director Michelle Chadwick and has been vetted and is endorsed by Professor Ron Grunstein, MBBS, MD, PhD, FRACP, and international Idiopathic Hypersomnia researcher Professor Karel Šonka MD, DSc.