A monster is choking you and there’s nothing you can do about it.

You’re asleep and you’re falling. You feel the rush of the air, the fear of the crash. You brace yourself for the inevitable impact. And then you wake up. You’re in your bed, and you’re completely fine. You fall back asleep and forget everything.

The phenomenon of falling during sleep is so common there’s a name for it: the hypnic jerk. The sensation is involuntary and usually triggered by anxiety or stress. Hypnic jerks are especially prevalent amongst children, but they lessen as we age.

Those who have experienced a hypnic jerk know the feeling can be unsettling and even scary. It’s not unusual for sleepers who have experienced one to wake up sweaty and rattled. But hypnic jerks are nothing when compared to the abject terror that accompanies sleep paralysis.

What is sleep paralysis?

Sleep paralysis is a sleep disorder where the brain is alert and awake, but the body is paralyzed. The condition is essentially the opposite of a night terror, in which the brain is asleep, but the body is still capable of thrashing around.

The disorder affects almost eight percent of the general population, and the phenomenon is more likely to occur among young adults and people struggling with mental health issues. There is no known cause for the disorder, but experts believe that stress, anxiety, alcohol, caffeine and jet lag can exacerbate its presence.

This is your brain on sleep

There are five stages of sleep, and it takes about ninety minutes for your brain to cycle through all of them. Sleep paralysis occurs during REM (rapid eye movement), the deepest stage of sleep in which dreaming occurs.

Your brain never takes a break, not even at bedtime. While you’re busy dreaming, your brain is using neurotransmitters to turn off the specialized cells that control motion. Theoretically, this is your brain’s way of deterring you from acting out your dreams and accidentally falling down the stairs in the process. But the one body part that your brain does not unplug is your eyes. This is why sufferers from sleep paralysis report being able to see during an episode, even when they lack control over the rest of their body.

A literal waking nightmare

80–90% of all sleep paralysis is accompanied by nightmares and disturbing hallucinations. Sufferers say that they wake up to the sounds of screaming and feel choked or experience severe pressure on their chest. Many claim to see ghosts or sense that other supernatural presences, like aliens or demons, are nearby. The sensations only dissipate after the sleeper is able to rouse himself.

According to a report in the journal “Consciousness and Cognition,” there are three types of hallucinations that sleepers experience:

  • A feeling that an intruder is present in the room
  • Difficulty breathing as a result of direct pressure applied to the chest or back
  • The sense that they are flying, floating or otherwise outside of their own body

Sleep paralysis is neither chronic nor dangerous and only 6% of people experience the disorder regularly. The phenomenon is often a side effect of other sleep issues, like insomnia, narcolepsy, PTSD and other anxiety or panic disorders.

For most people, sleep paralysis results in one terrifying night, but for those who experience it regularly, the disorder can be far more insidious. Regular sufferers tend to avoid sleep, dreading the hallucinations and terror they know to be imminent. This dread can eventually cycle into insomnia, depression and even suicidal thoughts and tendencies.

There is no cure for sleep paralysis, but the phenomenon does offer one benefit: if the sleeper is able to calm themselves down during the paralysis and return to sleep, they are sometimes able to access a state of lucidity, where, mentally, they can control the direction of their dreams.

And, really, isn’t that what we all want to do?