Sleep paralysis is the feeling of being paralyzed despite of being conscious and aware of the things that are happening around you. In 
addition, while in this state, the person who is experiencing this will not be able to move nor speak.
Dating back to the 10th century, sleep paralysis was believed to be caused by demons or spiritual possessions until the 19th century, when it was termed “sleep palsy” and eventually, “sleep paralysis”. If sleep paralysis occurs while falling asleep, it is called hypnagogic or predormital sleep paralysis and if it occurs upon waking up, it is called hypnopompic or postdormital sleep paralysis.
For the hypnagogic sleep paralysis, upon falling asleep, your body relaxes and usually you do not notice the changes because you are no longer aware of what is happening to your body. However, if you remain aware while falling asleep, you may notice that you cannot speak nor move. Conversely, for the hypnopompic sleep paralysis, during sleep, the body alternate between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep. NREM sleep occurs first then REM sleep. During NREM sleep the body enters the state of atonia which means relaxation of the muscles then entering almost the state of paralysis. At the end of NREM, your sleep shifts to REM hence, quick movement of eyes and it is where dreams occur. During REM sleep, all the muscles in the body are turned off and if you become aware before REM cycle ends, you may notice that you cannot move nor speak. Thus, creating hallucinations. Fortunately, most people who experience sleep paralysis need no treatments. Additionally, treating any underlying conditions such as narcolepsy may help if you are unable to sleep well and these treatments include: improving sleeping habits, using antidepressants, treating any mental health that may contribute to sleep paralysis and lastly, treating any other sleep disorders.
