A 15-year-old British girl fell asleep in April. But when she woke up, it was June.

The Sun reports on the curious case of Stacey Comerford, who has Kleine-Levin Syndrome, or Sleeping Beauty Syndrome. People with the condition have "episodes" where they sleep for as long as 20 hours a day for periods of time, according to the National Institutes of Health.

Comerford's latest period of time with the conditionlasted two months, The Sun reported.

"When she's in an episode, she might get up to go to the toilet or get a drink but she's not awake. I call it sleep mode," Comerford's mother, Bernie, told The Sun, adding that she feeds her when she's in this trance-like state. "When she wakes, she thinks it's the following day. She doesn't have any memory of it."

Bernie told the Daily Mail that when her daughter is having an episode, she reverts to a child-like state.

"When she's in sleep mode she can be quite moody but she can't help it," she told the Daily Mail. "She's like a toddler who wants to do things her own way. She stamps her foot if she doesn't get what she wants. It's like having two different kids in the house."

Stanford University's Center for Narcolepsy reported that Kleine-Levin Syndrome is actually a kind of rare sleep disorder that usually affects teens. However, people typically stop experiencing signs of the condition once they reach adulthood.

The cause of the condition is not entirely known, though scientists do suspect that it is an autoimmune disease, according to Stanford.

The National Institutes of Health reported that there is no exact treatment for the condition, and "watchful waiting" is typically the strategy of choice, rather than medication.

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