The most common symptoms shared by suffers of IH are:
- Greater than 10 hours sleep per 24 hour period – often as much as 16+ hours per 24 hour period
- Long unrefreshing naps that normally last several hours
- Awaking from sleep feeling unrefreshed, often with significant sleep inertia (commonly known as ‘sleep drunkenness’)
- An inability to be woken from sleep – even multiple alarm clocks or physical attempts made by family/friends are largely unsuccessful
- Cognitive problems caused by the overwhelming desire to sleep (commonly known as ‘brain fog’)
As the condition progresses less common symptoms can include:
- Anxiety and depression – often as a result of the limits this disorder creates on what is able to done with their time awake
- Raynaud’s type phenomena – freezing cold hands and feet
- Loss of impulse control – especially in regard to food
- Impotence
Those with IH often describe themselves as experiencing two types of sleepiness:
1) A physical exhaustion that ‘normal’ people might experience after missing several nights sleep in a row
2) A cognitive exhaustion similar to Executive Dysfunction that can make even simple tasks like reading, conversation with friends or watching a movie beyond their reach