A 15-year-old British girl often sleeps for months at a time.

''There's never any warning. I've even found her fast asleep on the kitchen floor.''

Stacey Comerford suffers from a rare condition called Kleine Levin meaning she sleeps for a lot of her life and can often drop off without any warning.

Her mum Bernie Richards said: ''There's never any warning. I've even found her fast asleep on the kitchen floor.''

But during one of Stacey's sleep episodes - which only see her wake up to use the toilet or grab a drink - she is partial to mood swings.

Stacey's condition has forced her to miss her birthday, nine exams and she has even slept through holidays.