Parasomnias are divided into two main categories based on whether or not they occur during REM (rapid eye movement) sleep.
Non-REM (NREM) Related Parasomnias
NREM-related parasomnias include behaviors like walking, talking, eating, urinating, or initiating sexual activity during sleep. These normally occur in the first half of the night and are generally related to repeated partial arousals from sleep. To a bed partner, you may seem distant or “zombie-like.” Despite being asleep, your eyes may be open. You probably won’t remember these episodes in the morning. Other common NREM parasomnias include confusional arousals -- stirring from sleep, maybe even sitting up in bed, and seeming confused -- and sleep terrors.
REM-related parasomnias normally occur in the second half of the night during “dream sleep.” These include nightmares and sleep paralysis (temporarily being unable to move as you wake up).
REM sleep behavior disorder -- or RBD -- is the most common REM-related parasomnia. Rather than staying paralyzed during sleep, you physically act out your dreams. Your behaviors and actions will seem purposeful (for example, punching or kicking), can be violent, and may be dangerous to you or your bed partner. Usually, your eyes stay closed. When you wake up, you quickly become alert and will often remember your dream. RBD can be a precursor to neurodegenerative diseases like Parkinson’s disease.