A black shadow persisted to hover and press against my chest. I couldn't breathe. I couldn't move. I was paralysed. I tried to speak, but no sound escaped my mouth.

What is Sleep Paralysis?

Sleep paralysis is a state, during waking up or falling asleep, in which a person is aware but unable to move or speak. The individual’s senses and awareness are intact, but they may feel as if there is pressure on them, or as if they are choking.

It may be accompanied by hallucinations and intense fear. Sleep paralysis is not life-threatening, but it can cause anxiety. It can happen alongside other sleep disorders, such as narcolepsy. It often starts during adolescence, and it can become frequent during the 20s and 30s. It is not a serious risk.

Between 8% and 50% of people experience sleep paralysis at some point in their life. Males and females are affected equally. Sleep paralysis has been described throughout history. It is believed to have played a role in the creation of stories about alien abduction and other paranormal events.

Symptoms

The main symptom of sleep paralysis is being unable to move or speak during awakening.

Imagined sounds such as humming, hissing, static, zapping and buzzing noises are reported during sleep paralysis. Other sounds such as voices, whispers and roars are also experienced. It has also been known that one may feel pressure on their chest.

These symptoms are usually accompanied by intense emotions such as fear and panic. People also have sensations of being dragged out of bed or of flying, numbness, and feelings of electric tingles or vibrations running through their body.

Sleep paralysis may include hypnagogic hallucinations, such as a supernatural creature suffocating or terrifying the individual, accompanied by a feeling of pressure on one's chest and difficulty breathing. Another example of a hallucination involves a menacing shadowy figure entering one's room or lurking outside one's window, while the subject is paralyzed.

Diagnosis

Sleep paralysis is not normally considered a medical diagnosis, but if symptoms are of concern, it may be a good idea to see a doctor.

Medical attention may help when:

Sleep paralysis happens regularly. 
There is anxiety about going to sleep or difficulty falling asleep
The individual falls asleep suddenly or feels unusually sleepy during the day
Suddenly falling asleep during the day could be a sign of narcolepsy, a rare brain disorder that causes a person to fall asleep or lose muscle control at unexpected or inappropriate times.

Medical treatment starts with education about sleep stages and the inability to move muscles during REM sleep. People should be evaluated for narcolepsy if symptoms persist. The safest treatment for sleep paralysis is for people to adopt healthier sleeping habits.