SIOUX CITY | A dark figure stands beside your bed and slowly leans in closer and closer to your face.
Startled, you jump out of bed.
Was it a nightmare?
Is your house haunted?
There's a scientific explanation for this seemingly supernatural phenomenon known as sleep paralysis, a disconnect between the rapid eye movement (REM) state and wake state. People have reported seeing ghost- or demon-like figures lurking over them or the feeling of an evil presence in their room upon waking in the middle of the night.
Mark Raymond, a neurophysiology technologist who started Mercy Medical Center's Sleep Lab in 1988, said these hallucinations could occur when you're falling asleep, but are more common when you wake up. The REM sleep cycle is longer in the morning. REM sleep is when people experience vivid dreaming.
"It's not unlike lucid dreaming. That's where you get into a dream and you know that you're in that dream and you can start acting out a bit," said Raymond, who recalls once shooting himself into space during a dream. Raymond, who is afraid of heights, said he woke up immediately.
"You can actually kind of train your brain so you can be aware of cues while you're sleeping that you are dreaming," he said.
Research shows that 25 to 50 percent of Americans will experience sleep paralysis at least once in their lives. Raymond said poor sleep, lack of sleep, stress, anxiety and some medications can make a person more prone to sleep paralysis, which is a symptom of narcolepsy, a chronic neurological disorder caused by the brain's inability to regulate sleep-wake cycles.
People with sleep paralysis might not have hallucinations, but find that they can't move.
"Your muscles are paralyzed because you're in REM sleep. A lot of people report they can open their eyes and see something coming, so it hasn't paralyzed the ocular muscles for some reason," he said.
What should you do if you have an episode or episodes of sleep paralysis?
In his 28 years of conducting sleep studies, Raymond said he can't recall a patient coming in specifically because they were only experiencing hallucinations during sleep or were paralyzed during sleep.
Raymond doesn't recommend calling your local Ghostbusters if you have an episode of sleep paralysis. He said you probably don't need to see a doctor either, unless the experience gives you anxiety.
"They might want to assess your sleep hygiene. Maybe you're taking your problems to bed," he said.
How to prevent sleep paralysis
Maintain a consistent bedtime.
Turn off electronic devices at least an hour before bedtime.
Write down the things that are causing you stress before going to sleep.
Meditate, take a warm bath or read a book before bed.
