What Makes Sleep Paralysis Scary?

“I couldn’t move! — It felt like someone else was in the room.” We wake up at times and get a familiar case like the aforementioned ones and wonder what happened. Was there really someone with us in our rooms at the same time we were mid-sleep? Perhaps an ominous being with bad intentions stopping us from getting up from our beds. Well, you can rest easy because it’s actually something that naturally occurs within our own bodies and there is no real outside danger as explained in this LiveScience article about what makes sleep paralysis scary.

This weird phenomenon is known as sleep paralysis, and a new study finds that understanding why it happens helps people feel less distressed after an episode. Believing that sleep paralysis is brought on by the supernatural, on the other hand, makes people feel more unnerved.

Sleep paralysis occurs when the brain and body aren’t quite on the same page when it comes to sleep. During rapid eye movement (REM) sleep, dreaming is frequent, but the body’s muscles are relaxed to the point of paralysis, perhaps to keep people from acting out their dreams. Researchers have found that two brain chemicals, glycine and GABA, are responsible for this muscle paralysis.

Estimates of how many people experience sleep paralysis vary from 5 percent to 60 percent, likely because of differences in survey methods. Some people find themselves experiencing sleep paralysis frequently, while others wake up paralyzed only once or twice in their lifetimes. The good news is that sleep paralysis is ultimately considered harmless.

Night terror

Becoming mentally aware before the body “wakes up” from its paralyzed state can be a terrifying experience, as people realize they can’t move or speak. Frequently, these episodes are accompanied by hallucinations and the sensation of breathlessness. Such hallucinations likely gave rise to the myths of the incubus and the succubus, demons that pin people down in their sleep (and sometimes have sex with them).

People may also sense a malevolent presence nearby or believe they are about to die. Some sleep paralysis episodes come with feelings of falling, floating or dissociating from the body.

These sensory experiences are more likely to distress people than mere paralysis alone, according to the study published online in February in the journal Clinical Psychological Science.

Researchers James Cheyne and Gordon Pennycook of the University of Waterloo in Canada surveyed 293 people, mostly women, on their experiences with sleep paralysis. They found that people were most distressed after an episode when hallucinations felt threatening and when they held supernatural beliefs regarding the cause of the paralysis.

Thinking away fear

People with analytical thinking styles were less likely to hold such supernatural beliefs, and were less likely to be distressed after experiencing sleep paralysis, the study found. Though the study couldn’t pin down the causal relationship, analytical thinkers may be more likely to seek out and believe naturalistic or scientific explanations for the condition, the researchers wrote, while intuitive thinkers might be drawn to supernatural explanations.

“These results suggest that it is not only important for clinicians to be aware of the implications of supernatural beliefs on SP [sleep paralysis] distress but also sensitive to the likelihood that not everyone will accept or experience relief from naturalistic interpretations,” the researchers wrote.

The online survey drew from a self-selected, rather than random, sample and relied on self-report, the researchers wrote. But allowing respondents to tell their stories can be important, they wrote, because patients complain that their doctors often dismiss the very real fear they feel when they wake up paralyzed.

Scented Sleep Can Wash Your Fears Away

Sleeping helps us reset our brains and calm our emotions. Perhaps it can do more, though: if sleepers are exposed to odours they associate with bad memories, it appears they can lose the fear those memories bring.

Previous studies have shown that sleep helps eliminate fear in general. But whether it is possible to focus this effect through the careful use of odours has not been tested in humans.

Katherina Hauner and Jay Gottfried of Northwestern University in Evanston, Illinois, exposed subjects to four pictures of faces and a series of inoffensive smells such as mint. When one of the faces appeared, the volunteers got a painful electric shock.

Afterwards, the researchers measured the amount of electricity conducted by the subjects’ skin – a measure that goes up when afraid, because the sweat produced is a good conductor. The researchers found that conductance spiked whenever the volunteers saw the face associated with the shock.

They then let half the subjects sleep, and exposed this group to variable amounts of the odour that had been presented along with the “painful” face. The next day, these volunteers were much less afraid of the face – and those with the least fear were those that had received the highest exposure to the odour while asleep. Brain scans also showed that brain areas associated with fear and with memory were less active after this exposure.

The other group of subjects stayed awake while they received pulses of the odour associated with the “painful” face. Unlike the sleeping group, however, these volunteers became more afraid of the face with greater exposure to the odour.

The question now is why sleep dissociates the fear from the image, rather than reinforcing the connection. Hauner says a clue may lie in reports from the awake volunteers, who said they saw the face in their minds every time they smelled the odour.

The technique could eventually enhance treatments for posttraumatic stress disorder by associating images from the traumatic memory with a smell, and then using odour exposure while sleeping, says Hauner. The next step is to study whether the effect occurs during REM sleep or slow-wave sleep.

Hauner’s team presented their study at the Society for Neuroscience. conference in New Orleans, Louisiana, last week.