Why do people laugh in their sleep?

Laughing during sleep, or hypnogely, is relatively common and is not usually anything to worry about. In most cases, researchers believe that the cause is laughing at a dream during rapid eye movement sleep, which is entirely harmless.

In some cases, sleep laughing has links to sleep disorders. In rare cases, hypnogely can be a symptom of a neurological disorder.

Although Sigmund Freud and other prominent psychoanalysts have attributed sleep laughing to an unconscious manifestation of primal instincts and fears, experts dismiss this theory as not being entirely credible. Is it normal?

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