nightmares are unpleasant dreams that cause fear, anxiety, or distress. They usually occur during the rapid eye movement (REM) stage of sleep, when the brain is most active and vivid dreaming happens. nightmares may be triggered by stress, trauma, emotional issues, medication, or other factors. They can affect anyone, but are more common in children and people with mental health problems. nightmares are not harmful in themselves, but they can interfere with sleep quality and daytime functioning. If nightmares are frequent or severe, they may indicate a sleep disorder or an underlying psychological condition that requires treatment.
