A neuroscientist breaks down a common misconception about a rare sleep disorder.

In an Instagram post, Ben Rein, PhD, explains the difference between narcolepsy and cataplexy.

Narcolepsy is a chronic neurological sleep disorder that affects the brain’s ability to regulate sleep-wake cycles. It often causes excessive daytime sleepiness, sudden sleep episodes, sleep paralysis, and vivid hallucinations.

Cataplexy is not a separate disorder—it is a symptom of narcolepsy type 1 that causes sudden muscle weakness triggered by strong emotions such as laughter or surprise. A person remains fully awake during these episodes, but muscle control may weaken from a slight droop to a complete collapse.

In short:

Narcolepsy = the disorder
Cataplexy = a possible symptom involving sudden muscle weakness
People can experience cataplexy without narcolepsy, though it is rare
All people with cataplexy have narcolepsy, but not everyone with narcolepsy has cataplexy