The reason behind sleep-talking is not completely understood at this point, however, it is mainly believed to be caused by unrepressed brain signals.
The act of talking while sleeping is actually called somniloquy, however we average people know it simply as sleep-talking. Sleep-talking is actually a type of sleep disorder, in which a person talks during their sleep. This ‘talk’ can range from simple nondescript mumbling to a full on conversation. It may even include a loud shouts or screams. However, most people do not even know that they sleep-talk as they have no memory or sensation of that event. In fact, until someone overhears them and tell them, most sleep-talkers will go through life without ever finding out.
Sleep-talking is more common in children than in adults. In fact, about 50% of children actually experience sleep-talking. Most of them actually outgrow it by puberty. Only 4% of adults reportedly talk in their sleep. Sleep-talking may occur by itself or as part of sleepwalking, night terrors, rapid eye movement behavior disorder (RBD), or Sleep-related eating disorder (SRED).
Additionally, certain factors increase the risk of sleep-talking, such as if your parents were sleep-talkers. It is believed that sleep-talking like sleepwalking is hereditary. However, sleep-talking is also possible if neither parents were sleep-talker, but the chances of it occurring are drastically reduced. Also, there are a large portion of adults who start talking later in life without any history of sleep-talking.
There are many other factors that may create an onset of sleep-talking or lead to frequent bouts of sleep-talking. These include increased stress, lack of sleep, as well as not eating enough, or eating heavy meals just before bedtime.
Sleep-talking commonly occurs during the less-deep non-rapid eye movement (NREM) phase of the sleep. Sleep-talking also does occur during other periods of sleep, however it is less common.
The reason behind sleep-talking is not completely understood at this point, however, it is mainly believed to be caused by unrepressed brain signals. During sleep, our body is relaxed, however our mind is still active; hence, it continues to send the body signals to act and speak. However, as we are asleep these signals need not be followed; hence other neurological mechanisms suppress these commands. In sleep-talkers, these signals are not properly suppressed at times. During these times, some of these commands are followed by the body unconsciously. The effect of this is that the person either sleep-talks or sleepwalks without having any memory of it.
Sleep-talking is mainly harmless. The only risk that one runs during sleep-taking is to accidentally offend the person who is listening. This is very possible as some sleep-talkers take the name of the person they are dreaming about, or their sleep-talking may be dramatic, emotional, or even profane. Also, if the listener is does not know about the sleep-talking, they may mistake their utterances as being conscious speech.