Narcolepsy is a neurological disorder that alters sleep-wake cycles, the 24-hour biological cycles of sleep and wake that drive our urge and need for rest and activity. Narcolepsy is perhaps best known for a single symptom—a sudden, overwhelming urge to sleep that can occur at any time. These abrupt episodes of intrusive sleep are often referred to as sleep attacks. But the sleep disorder, which affects roughly 1 in 2000 people, has a cluster of debilitating and disruptive symptoms that can affect a person’s sleep and waking life. In addition to sleep attacks, narcolepsy is often characterized by:

Excessive daytime sleepiness. Along with sleep attacks, this is the most common symptom of narcolepsy. People with narcolepsy can experience persistent and severe tiredness during the day, which often isn’t relieved by sleep.

Restless nighttime sleep. Because their sleep-wake cycles are in an ongoing state of disruption, people with narcolepsy often don’t sleep soundly at night. They may experience symptoms that are similar to insomnia, including difficulty falling asleep and waking often throughout the night.Narcolepsy

Cataplexy. This refers to a sudden loss in muscle tone that can overtake people with narcolepsy. Episodes of cataplexy appear to be triggered by intense emotions, both positive and negative: shock, anger, excitement, amusement, joy, fear. The degree of muscle-tone loss in cataplexy can vary widely among people with narcolepsy. In some cases, cataplexy can be relatively mild and limited to certain muscle groups. In other cases, episodes of cataplexy can affect the entire body, and cause slurred speech, collapse, and temporary paralysis. Not all people with narcolepsy experience cataplexy.

Sleep-related hallucinations. People with narcolepsy can experience disorienting, sometimes scary visions as they drift off to sleep or upon awakening. These hallucinations often involve elements of fear, such as falling, seeing a dark figure nearby, or sensing a presence in the room. Sleep-related hallucinations aren’t only experienced by people with narcolepsy—they are one type of parasomnia that can happen to anyone. But people with narcolepsy are more likely than other people to have these sleep-related hallucinations.

Sleep paralysis. This is another frightening and difficult symptom of narcolepsy. Sleep paralysis occurs in the midst of waking or falling asleep, when a person becomes aware that they cannot move or open their mouths to speak. Sleep paralysis can last for just a few seconds, or may persist for a minute or more. Like sleep-related hallucinations, sleep paralysis isn’t exclusively a symptom of narcolepsy, and not everyone with narcolepsy will experience these disturbing episodes of paralysis. But people with narcolepsy are at greater risk for sleep paralysis than people without.

Narcolepsy can have a powerfully limiting effect on people’s lives as it  may interfere with nearly every aspect of daily life. Sleep attacks can occur suddenly at any time, which can make normal, routine activities like driving dangerous.

What causes narcolepsy? Narcolepsy has been linked in scientific studies to deficiencies in a particular neurotransmitter that helps to regulate wakefulness. Scientific research suggests there may be a genetic component to the sleep disorder. Environmental factors are also considered possible triggers. Scientists are investigating the possibility that narcolepsy may be linked to immune system dysfunction.

Treatment for narcolepsy usually involves medication to help alleviate sleepiness and sleep attacks, as well as lifestyle changes and careful adherence to sleep routines, including regular sleep schedules and scheduled naps.

For more information about Narcolepsy, check out Project Sleep.