A hypnic jerk, or sleep start, is a sudden muscle contraction that jolts you awake just as you’re drifting off. “Up to 70% of individuals report having this abrupt and surprising jolt.”
The exact cause remains unclear, but one theory suggests that as the body relaxes, the brain misinterprets it as falling, triggering a reflex to “catch” the body. Another theory links it to the brain struggling to transition smoothly into sleep, causing miscommunication between the brain and body.
Factors like stress, fatigue, and anxiety may increase the likelihood of hypnic jerks, as an overactive nervous system is more prone to such reactions.
Though startling, these jerks are harmless. “Understanding that they are a normal part of the sleep process can help reduce anxiety about them,” making it easier to fall back asleep.
