“Waking a sleepwalker is dangerous for them.”

The idea that waking a sleepwalker is dangerous, potentially causing a heart attack or brain damage, has roots in historical misunderstandings and cultural fears surrounding this mysterious nighttime phenomenon. For centuries, before scientific understanding of sleep, sleepwalking was often attributed to supernatural (Review) forces. In medieval times, some believed the soul left the body during sleep, and a sudden awakening could leave a person "soulless" or otherwise gravely afflicted. Such folklore and old wives' tales, often dramatized in literature and popular culture, cemented the misconception that rousing a sleepwalker could lead to severe harm.

Modern sleep science, however, has thoroughly debunked the notion of physical danger like heart attacks or brain damage from waking a sleepwalker. Neurologists confirm these stories are pure myth. Sleepwalking, or somnambulism, occurs during a partial arousal from deep, non-REM sleep, meaning the individual is in an in-between state of being partly awake and partly asleep. The actual concern with abruptly waking a sleepwalker stems from their likely reaction rather than any inherent physical harm.

People often believe the myth because there is a practical "nugget of truth" in the advice to avoid startling them. If suddenly awakened, a sleepwalker can become extremely confused, disoriented, or frightened, much like someone suddenly roused from a very deep sleep in an unfamiliar place. This startled response could lead them to lash out defensively, trip, fall, or accidentally injure themselves or others as they struggle to understand their surroundings. Therefore, while waking them isn't inherently dangerous to their health, the safest and most recommended approach is typically to gently guide them back to bed without fully waking them, ensuring their environment is clear of hazards.