Qs people asked me on science and my replies to them - part 171

Q:Sometimes I feel someone is giving me an immediate push while I was asleep, like a ghost kicking me with a sound which makes me wake up. What might be happening?

Krishna: After reading your question, I could think about a few things. 

1. Sleep paralysis: Up to as many as four out of every 10 people may have sleep paralysis. This common condition is often first noticed in the teen years. But men and women of any age can have it.
During sleep, your body alternates between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep. One cycle of REM and NREM sleep lasts about 90 minutes. NREM sleep occurs first and takes up to 75% of your overall sleep time. During NREM sleep, your body relaxes and restores itself. At the end of NREM, your sleep shifts to REM. Your eyes move quickly and dreams occur, but the rest of your body remains very relaxed. Your muscles are "turned off" during REM sleep. If you become aware before the REM cycle has finished, you may notice that you cannot move or speak.

Explanations about this sensationalist events —can have a profound impact on how people experience sleep paralysis. Beliefs about the disorder heightens symptoms in a bizarre mind-body interaction with “nocebolike” effects (2). An active imagination had the astonishing ability to shape physiological experiences. Based on research findings, it appears that the more people fear sleep paralysis, the more they experience it, and the stronger its effects are. What were once thought to be benign, even inventive, beliefs have transformed the disorder, triggering conditioned fear and coloring the content of hallucinations. Anxiety and stress predispose people to an attack, so those who dread it are often more likely to experience it. 

If you find yourself unable to move or speak for a few seconds or minutes when falling asleep or waking up, then it is likely you have isolated recurrent sleep paralysis. During this time, you might 'feel' your dreams are true and if they are nightmarish, you think you are dealing with ghosts, which is not actually true.

Sleep paralysis is caused by what appears to be a basic brain glitch at the interface between wakefulness and rapid eye movement (REM) sleep (1). During REM, you have intensely lifelike dreams. To prevent you from acting out these realistic dreams (and hurting yourself!), your brain has a clever solution: it temporarily paralyzes your entire body. Indeed, your brain has a “switch” (a handful of neurochemicals) that tilts you between sleep and wakefulness. Sometimes the “switch” fails, however—your brain inadvertently wakes up while your body is still under the “spell” of REM paralysis, leaving you stuck in a paradoxical state between parallel realities: wakefulness and REM sleep. During sleep paralysis, the crisp dreams of REM “spill over” into waking consciousness like a dream coming alive before your eyes—fanged figures and all.

These hallucinations—often involving seeing and sensing ghostly bedroom intruders—are interpreted differently around the world.

Factors that may be linked to sleep paralysis include: Lack of sleep, sleep schedule that changes, mental conditions such as stress or bipolar disorder, sleeping on the back, other sleep problems such as narcolepsy or nighttime leg cramps, use of certain medications, such as those for ADHD, substance abuse.

Usually, you don’t need to go for a treatment. But treating any underlying conditions such as narcolepsy may help if you are anxious or unable to sleep well. Improve your sleeping habits. Try to reduce your stress levels.

2. Hypnic jerks: Hypnic jerks, which people also refer to as hypnagogic jerks or “sleep starts,” are involuntary muscle contractions that some people experience as they are falling asleep.  It tends to happen just as the person is transitioning from a wakeful state to a sleeping state. Some hypnic jerks are mild and hardly noticeable. Others can be intense — anyone who has been close to falling asleep and then felt a sudden jerk that has woken them up has experienced a hypnic jerk. It is possible to wake up from a hypnic jerk, but this does not always happen, as the strength of the muscle contraction that a person experiences will vary. In some cases, these large contractions can make a person feel as though someone else is pushing them off the bed. The other symptoms of a hypnic jerk may also wake the person up. Sometimes the person dreams that they are falling either out of bed, from a tree, or through a void. Although it is uncertain which sensation comes first, this can be enough to scare the person awake.

Hypnic jerks are common and occur randomly. The exact cause of these twitches is unclear, but some factors may increase their likelihood.

Hypnic jerks are a type of involuntary muscle movement called myoclonus. Hiccups are another common form of myoclonus. The strength of a hypnic jerk may vary. Some people may not be aware of the twitches, and may only know that they experience them if somebody else notices the movements. Other times, the spasms can be strong enough to startle the person and wake them up.