A nightmare is a disturbing dream associated with negative feelings, such as anxiety or fear. Nightmares usually occur during the stage of sleep known as rapid eye movement (REM). You normally go through four to six sleep cycles a night, cycling through the sleep stages in about 90 minutes. Your REM stage lengthens with each cycle, from several minutes in the first cycle to up to an hour in the last. You’re more likely to have a nightmare in the second half to the last third of your night.
A nightmare may involve these features:
- Your dream seems vivid and real, often becoming more disturbing as the dream unfolds
- Your dream storyline is usually related to threats to your safety or survival
- Your dream wakes you
- You feel scared, anxious, angry, sad or disgusted as a result of your dream
- You feel sweaty or have a pounding heartbeat, but do not leave the bed
- You can think clearly upon awakening and can recall details of your dream
- Your dream occurs near the end of your sleep time
- Your dream keeps you from falling back to sleep easily