Is "Waking a sleepwalker is dangerous and can cause a heart attack or brain damage" true?
Horror movies and grandparents agreed: never wake a sleepwalker or you risk a heart attack, brain damage, or worse. That fear kept families gently herding wanderers back to bed for generations. Neurologists say the medical catastrophe story is folklore. Sudden waking can startle someone into confusion or accidental injury, so guiding them calmly is still wiser, but it does not stop a heart or scramble a brain.
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What you were taught
Waking a sleepwalker is dangerous and can cause a heart attack or brain damage
What we know now
Waking a sleepwalker does not cause a heart attack, brain damage, or death; neurologists describe those claims as myth. Sleepwalking (somnambulism) is a partial-arousal disorder, usually in deep non-REM sleep early in the night. Abrupt waking can produce temporary confusion or a startle response that might lead to falls or thrashing, so gently guiding the person back to bed is preferred when possible—but the danger is incidental injury and agitation, not catastrophic medical harm.
Was "Waking a sleepwalker is dangerous and can cause a heart attack or brain damage" taught in school?
Yes — and not as a joke question on a quiz. This health claim showed up in textbooks, worksheets, and classroom posters through the 2010s, which is why so many people still remember it as settled fact long after the science moved on.
Is "Waking a sleepwalker is dangerous and can cause a heart attack or brain damage" true?
No. Waking a sleepwalker does not cause a heart attack, brain damage, or death; neurologists describe those claims as myth. Sleepwalking (somnambulism) is a partial-arousal disorder, usually in deep non-REM sleep early in the night. Abrupt waking can produce temporary confusion or a startle response that might lead to falls or thrashing, so gently guiding the person back to bed is preferred when possible—but the danger is incidental injury and agitation, not catastrophic medical harm. If you want the primary citation, start with BrainFacts/SfN - Is It Dangerous to Wake a Sleepwalker?
When was this understanding updated?
The evidence had largely shifted by around 2019. Schools don't flip overnight, though — plenty of classrooms kept teaching the older version for years after researchers had already moved on.