Over the centuries, symptoms of sleep paralysis have been described in many ways and often attributed to an "evil" presence: unseen night demons in ancient times, the old hag in Shakespeare's Romeo and Juliet, and alien abductors. Almost every culture throughout history has had stories of shadowy evil creatures that terrify helpless humans at night. People have long sought explanations for this mysterious sleep-time paralysis and the accompanying feelings of terror.
- 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