Sleep talking, also known as somniloquy, is a parasomnia disorder that is harmless but nonetheless is viewed as problematic and even unsettling by some. Some sleep talkers only mumble sounds, while others may ramble off long and complex strings of sentences. While the details of the effects of the disorder are fairly straightforward, the "why" behind it all is decidedly more complex.
Typically, sleep talking happens during periods following or during REM sleep, as transitory arousals occur. Consciousness does not exist and the sleep talker can neither control nor be aware of their speech. Sleep talking is not purely native to REM-based sleep circumstances, however, and can also occur during NREM sleep. In the case of NREM, sleep talking constitutes what is known as a motor breakthrough. A motor breakthrough occurs because the words spoken in a dream--the dream speech--are actually spoken aloud in the realm of reality. Hence, the boundaries between reality and the dream world are broken down in sleep-talking during NREM sleep.
Sleep talking isn't always a solitary phenomenon. While sleep talking can occur all on its own, it often comes paired with another sleep disorder. Such sleep disorders that may come paired with sleep talking include night terrors, sleep-related eating disorder (SRED), REM Sleep behavior disorder (RBD) and sleepwalking. While most of these are self-explanatory, REM sleep behavior disorder is characterized by disruptive and even obscene sleep talking.
Sleep talking is considered harmless and does not require treatment; it often occurs randomly in people, especially younger children, and may be (but not necessarily) caused by another sleep disorder (see above), substance abuse, a mental health disorder, use of prescription drugs or a preexisting medical condition. Sleep talking can occur in up to 50 percent of children, but it tends to disappear after puberty, with only roughly 5 percent of adults experiencing the phenomenon. Men and women are equally susceptible to the disorder, and sleep talking has been known to run in families.
While dedicated medical help for sleep talking isn't necessary, for peace of mind or to possibly discover an underlying reason for the phenomenon, a friend or partner may assist in monitoring the sleep talking events. If a friend or loved one is not available to help, an audio recording device may be used, particularly one which records sounds only when sounds are present. If this device or a friend records profane use of language during sleep talking, this can be an indicator that another sleep disorder is at work.