Sleepwalking, or somnambulism, happens during deep non-REM sleep — notably not during REM sleep, which is when most vivid dreaming occurs. This is one of the most persistent misconceptions about it: sleepwalkers are not acting out a dream. Their brain is in a genuinely unusual state, partway between deep sleep and wakefulness, capable of complex movement without the awareness that would normally accompany it.
What's happening in the brain
During a sleepwalking episode, the parts of the brain responsible for movement and basic function are active, while the areas responsible for conscious awareness, memory formation, and full alertness remain in a deep-sleep state. This split explains the classic features: purposeful-looking movement, open eyes, sometimes speech, but a blank or confused expression and no memory of it afterward.
Is it safe to wake someone sleepwalking?
Yes — the old belief that waking a sleepwalker is dangerous is a myth. It's not harmful, though the person may be confused or briefly disoriented upon waking. The bigger practical concern is safety during the episode itself: sleepwalkers can navigate stairs, unlock doors, and move through their environment while genuinely unaware of real hazards, so gently guiding someone back to bed, or ensuring a safe environment, matters more than whether or not to wake them.
Who it affects
Sleepwalking is most common in children, who typically grow out of it, but it persists or begins in adulthood for some people. It tends to increase with sleep deprivation, stress, fever, alcohol, and an irregular sleep schedule — all factors that make it harder for the brain to complete a clean transition through sleep stages.