Idiopathic hypersomnia is an uncommon sleep disorder that causes you to be very sleepy during the day even after a full night of good sleep. Its cause is unknown. It also often causes difficulty waking up after you've been asleep. If you take a nap, you generally don't feel refreshed and you may wake up confused and disoriented.

The need to sleep can strike at any time, including when you're driving a car or working, which makes idiopathic hypersomnia potentially dangerous.

The condition often develops gradually. Diagnosing idiopathic hypersomnia requires ruling out more-common sleep disorders. The aim of treatment is to control symptoms with medication.