Sleep paralysis - Causes of sleep paralysis
NHS Choices Medical Reference
Sleep paralysis is caused when hormones produced
by the body to help you sleep do not wear off as you wake up.
This means that you remain temporarily paralysed but conscious.
To understand better what causes sleep paralysis, it is useful to know what usually happens when you are asleep.
Sleep occurs in cycles and each cycle is split into two phases - rapid eye movement (REM) sleep and non-REM sleep.
The brain is very active in REM sleep and most dreams occur at this stage of sleep. Also, during REM sleep the body is paralysed, apart from the movement of the eyes and diaphragm (the main muscle used in breathing). The paralysis is thought to occur to prevent you acting out the actions in your dreams.
Sleep paralysis occurs when the normal muscular paralysis of REM sleep temporarily continues after you have woken up.
Certain factors make you more likely to get sleep paralysis:
age - it is more common in teenagers and young adults
sleep deprivation - sleep paralysis is more common in people who do not get enough sleep
irregular sleeping patterns - people with irregular schedules or who work shifts are more prone to sleep paralysis
narcolepsy - some people with narcolepsy (a sleep disorder where you suddenly fall asleep at inappropriate times) also experience sleep paralysis
family history - you may be more likely to have sleep paralysis if another member of your family also has it; however, this is an area where further research is needed