Snopes investigates the old myth holds that waking a sleepwalker could cause serious harm.

Claim: Waking up a sleepwalker could cause the person to have a heart attack, go into a coma, or experience other serious medical conditions.

Origin: In late October 2020, a video on the social media platform TikTok went viral. It appeared to show a man in the process of sleepwalking as he mimes eating with a fork in his hand. The man is startled awake when the person holding the camera shouts at him, and he reflexively throws the fork at her.

snopes.com