A French study found that the most common phrases spoken during sleep-talking episodes include profanities and the word "no."

The study included 232 adults – 15 were healthy participants, while the rest suffered from parasomnias (sleep disorders).

The researchers were able to record about 900 sleep-talking episodes from the participants during one or two consecutive nights in a laboratory. The utterances were analyzed for a variety of factors including: number of words spoken; propositions; frequency, gaps and pauses (denoting turn-taking in conversation); verbosity; tone; first/second person; politeness; and abuse, according to the study.

Fifty-nine percent of the utterances were either nonverbal or couldn’t be understood due to mumbling, whispering or laughing.

But out of the sleep-talking phrases that could be analyzed, 24 percent contained negative content, 22 percent had “nasty” language and nearly 10 percent contained the word “no” in some form. For reference, “no” accounted for 2.5 percent of awake language.

Profanity words were used during sleep more than 800 times as often as when awake. Other than “no”, the “F-word” was one of the most common words spoken while asleep.

According to the study authors, verbal abuse lasted longer in REM sleep and was mostly directed toward insulting or condemning someone, whereas swearing predominated in non-REM sleep.

The team also noted that overall, men sleep-talked more than women and used a higher rate of profanities.

Some theories suggest that dreaming has an evolutionary purpose – dreams simulate threats that could occur while awake to better prepare individuals for those potential scenarios. With this logic, it would make sense that many of the words were negative or profanities.

They also found that sleep talking remained grammatically correct and followed patterns of everyday speech in terms of pauses and number of words in a statement. This finding demonstrates that the sleeping brain can still function at an elevated, complex level.