Why do we dream?
Scientists do not fully know why we dream. Leading ideas say dreams help the brain sort memories, process emotions and rehearse responses to threats.
Most vivid dreams happen during rapid eye movement, or REM, sleep, when the brain is very active but the body's muscles are mostly paralyzed. Adults go through several REM periods a night and spend about two hours dreaming in total, though most dreams are quickly forgotten.
One theory says dreams help strengthen memories and link new information to older knowledge. Another suggests they help us cope with emotions by replaying feelings in a safer setting. The threat simulation theory proposes that dreams let us practice reacting to danger.
Nightmares and lucid dreams
Nightmares are common, especially during stress. Some people have lucid dreams, in which they know they are dreaming and can sometimes control what happens. Scientists study both to learn more about how the sleeping brain works.
Did You Know?
People who are blind from birth dream too. Their dreams involve sounds, touch, smell and taste rather than images.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.