On Health.com, experts explain sleep paralysis symptoms, causes, and treatments—and reveal that it’s more common than you probably realize. 

Sleep paralysis occurs when you’re in a borderline state between sleep and consciousness as you’re dozing off or waking up, says Dr. Kushida. Researchers don’t understand why this temporary loss of voluntary muscle control happens. “One theory is that there’s some crossover with rapid eye movement (REM) sleep, also known as dream sleep,” says Neil Kline, DO, a sleep disorder physician in Lancaster, Pennsylvania and a representative of the American Sleep Association.