Cataplexy is a sudden and transient episode of loss of muscle tone, often triggered by emotions. It is a rare disease (prevalence of fewer than 5 per 10,000 in the community), but frequently affects people who have narcolepsy, a disorder whose principal signs are EDS (Excessive Daytime Sleepiness), sleep attacks, sleep paralysis, hypnagogic hallucinations and disturbed night-time sleep. Cataplexy is sometimes confused with epilepsy, where a series of flashes or other stimuli cause superficially similar seizures. Cataplexy can also be present as a side effect of SSRI Discontinuation Syndrome.