Parasomnias can be described as “strange things that go bump in the night”. They are a group of acute, undesirable, episodic physical phenomena that usually occur during sleep, or are exaggerated by sleep. Even though parasomnias occur during different stages of sleep and at different times during the night they are characterized by partial arousals before, during, or after the event. It intrudes into the sleep process and creates disruptive or abnormal sleep events. It's believed that these abnormalities occur in a mixed state of sleep and wakefulness, where the sleeper is alert enough to perform complex behaviors, yet remains unaware of his or her actions. Typically these occurrences do not indicate significant psychiatric or psychological problems. These disorders are often hereditary and are often more severe when you are sick, sleep deprived, or taking certain medications.

Another factor to consider is stress. During increased times of stress, parasomnias may be seen more frequently, precipitated or perpetuated. Parasomnias are usually accompanied by periodic limb movements, like: twitching, jerks of the arms or legs which cause repeated arousals. When parasomnia persists most nights a week for weeks, it can cause increased tension, decreased energy, and personality and mood changes.

Examples of parasomnias are:

	Sleepwalking
	Teeth grinding
	REM sleep disorder
	Sleep-awake transition disorders, etc.
	Arousal disorders (presumed to be due to an abnormal arousal mechanism)

The best know parasomnia is sleepwalking, which is thought to afflict as much as 18% of the population. As is well known, sleepwalkers can venture out of the house into traffic and even walk through glass windows, harming themselves. When they wake up,the remember nothing.