Hypnic Jerk: What Is It, Causes and How to Stop

The exact cause of hypnic jerks is not yet known to researchers. Existing literature on this subject explains that a hypnic jerk or a sleep start occurs in the same brain region responsible for you to feel scared or startled. 

According to researchers, when we are drifting into sleep, sometimes a misfire occurs between nerves in the reticular brainstem that triggers a reaction, which leads to a hypnic jerk. 

How does this misfire occur? 

Well, say you are trying to fall asleep and your muscles relax completely. But, your brain may assume you are falling down from a certain height and react to it by involuntary muscle contraction. Hypnic jerks may not always be spontaneous, it can also be a physical reaction to a mental image or hallucination or dream-like imagery that is associated with them. 

A visual sleep start occurs when you see or have a sensation of blinding light coming from your head or inside the eyes. Some people hear a loud snapping noise coming from inside the head, which refers to an auditory sleep start. ‘Sensory sleep starts’ occurs when you experience only sensory phenomena without any jerk in the body. 

Researchers have identified some factors that increase the risk of experiencing a hypnic jerk and are listed below:

Sleep Deprivation

Lack of restful night sleep due to insomnia or hectic work schedule or poor sleep quality leads to sleep deprivation. Leaving your sleep unaddressed may lead to hypnic jerks besides poor concentration and low mood.

Trouble sleeping and lack of regular sleep overall, whether due to chronic insomnia or a poor night’s sleep, can both lead to sleep deprivation. Among other unwanted side effects, like poor mood and focus, sleep deprivation may increase your risk of jerking in sleep.

Stress and Anxiety

Main hypnic jerk causes are stress and anxiety. But what does it mean if you experience hypnic jerks or body jerks due to anxiety?

People diagnosed with anxiety disorder and stress are highly likely to experience insomnia, which leads to sleep deprivation and consequently hypnic jerks. Excessive stress and anxious thoughts increase the levels of stress hormone – cortisol that deprives you of good quality sleep. When you don’t relax while sleeping, it disturbs the transition between wakefulness and sleep, which is why you twitch before falling asleep.

Again people who frequently experience hypnic jerks develop anxiety around sleeping at night, which in turn increases sleep deprivation and frequency of hypnic jerks.

Exercise

No doubt, exercise improves physical and mental health and sleep quality. However, it makes you feel more alert and not exhausted. So, vigorous exercise especially in the late evenings may increase the frequency of sleep starts.

Excessive Caffeine or Nicotine Consumption

Taking caffeine or nicotine products before bedtime can increase your risk of twitching before falling asleep. Both nicotine and caffeine stay in our system for long hours and keep our brain alert and delay the onset of sleep. Those who drink coffee a full six hours before bed also have trouble falling asleep. 

So avoid such stimulants in the late afternoons and evenings to prevent sleep-onset insomnia. 

Evolutionary hypothesis

One study suggests that the origin of hypnic jerks dates back to our evolutionary ancestors. As per the hypothesis, sleep twitching helped primates readjust their sleeping positions or positions before they entered a deep sleep state. When sleeping in uncomfortable places like tree trunks or rocks, the brain interpreted the transition to relaxation as a threat to their survival. A hypnic jerk prevented the primates from falling out of a tree or getting hurt during their restful night’s sleep.