Narcolepsy is a neurological disorder that is primarily believed to be related to disruptions in the sleep cycle, particularly with the rapid eye movement sleep cycles that many people refer to as REM sleep.
This disorder can be diagnosed in nearly anyone, but is it typically diagnosed between the ages of 7 and 25.
The most commonly documented symptoms that are associated with narcolepsy are:
- Excessive daytime sleepiness (EDS): Individuals diagnosed with narcolepsy display extreme episodes of daytime sleepiness. These episodes are far more severe than normal feelings of lethargy, fatigue, or sleepiness that many individuals experience from time to time. Individuals who have EDS will often experience numerous involuntary sleep episodes where they actually fall asleep for a few seconds or more numerous times during the day. They often continue to perform the behaviors that they were performing before the involuntary sleep episode occurred, which can include writing, talking, walking, driving, etc. Often, the only clue that they have to indicate that they drifted off to sleep is the disruption in their behavior pattern during the involuntary sleep episode. For instance, someone driving a car and having an involuntary sleep episode may actually go off the road briefly, or someone writing a letter or dictating a report may look back and notice intermittent sections where they wrote or recorded gibberish. Obviously, this manifestation of narcolepsy can result in some potentially hazardous situations for both the individual and others around them, and these individuals need to be restricted until these involuntary sleep episodes can be controlled.
- Issues with nighttime sleep: Despite the common manifestation of EDS and potential involuntary sleep episodes, individuals with narcolepsy often experience issues with sleeping at night. These issues can include initial insomnia (difficulties falling asleep or initiating sleep), waking up in the middle of the night and being unable to return to sleep (middle insomnia), issues with vivid dreams that may be disturbing and often wake them, and involuntary limb movements that wake them up. Once these individuals wake up, they have extreme difficulty returning back to sleep. In some instances, individuals who experience very vivid dreams may find themselves acting them out.
- Sleep paralysis: Sleep paralysis occurs when an individual is either drifting off to sleep or waking up and has the sensation that they are paralyzed or they cannot move at all. This is a common occasional occurrence for many people; however, individuals with narcolepsy may experience numerous episodes of sleep paralysis that are sometimes accompanied by very vivid visual hallucinations. Most often, the hallucinations are visual in nature, but they can be auditory, tactile, or even olfactory. Hypnagogic hallucinations are hallucinations that occur when one is falling asleep, whereas hypnopompic hallucinations result when one is waking up.
- Cataplexy (drop attacks): Some people who are diagnosed with narcolepsy experience periods where they have a severe loss of muscle tone, muscle control, and an inability to make voluntary movements. In extreme cases, the individual may lose the entire ability to control themselves and collapse even though they are totally conscious. During these drop attacks, individuals are still conscious and aware but they cannot speak or even open their eyes. In some individuals, a number of events can trigger drop attacks, such as emotional episodes or even eating a heavy meal.
- Obesity: In many cases, individuals with narcolepsy may gain weight once the disorder occurs.
Narcolepsy is often divided up into two subtypes. Narcolepsy type I is often labeled in individuals who have narcolepsy with cataplexy, whereas narcolepsy type II is often the label use for individuals who have narcolepsy but do not experience cataplexy. Narcolepsy is relatively rare, and the prevalence rate for narcolepsy is often reported as being around 1:2000. It appears equally common in men and women. There is no known cause for this disorder and it is believed that there is a strong genetic component associated with the disorder, even though a large number of individuals diagnosed with narcolepsy have no family history of the disorder.
There is ongoing research that has suggested that low levels of a neurotransmitter known as orexin or hypocretin may be associated with the disorder, and some forms of narcolepsy may be associated with the loss of neurons in the brain that produce this neurotransmitter. This research indicates that at least some cases of narcolepsy may result from an autoimmune disorder that results in the loss of these neurons and that this autoimmune disorder may have a genetic component. In rare cases, individuals who experience traumatic brain injuries may develop narcolepsy, further suggesting that disruption of specific categories of neurons may be one potential cause of the disorder.
- Diagnosing Narcolepsy
Since narcolepsy is a neurological disorder, it can only be diagnosed by a physician, preferably a neurologist. Some of the assessments used to assist in the diagnosis of narcolepsy include:
- A thorough examination: A thorough medical evaluation that includes a full medical history and physical examination is needed.
- Multiple sleep latency tests: These tests are performed when the person is awake to determine and measure whether or not the individual is having involuntary sleep episodes that include intrusive REM sleep episodes. These tests also measure all of the individual’s physiological activities.
- Polysomnogram: This test measures numerous physiological activities when the individual sleeps and can reveal if the person has any difficulties with REM sleep.
- Spinal tap: This test can be used to measure levels of hypocretin in the spinal fluid and determine if these levels are low. If they are and the person presents with symptoms of narcolepsy, this is often taken as a diagnostic marker.
- Self-report measures: In many cases, certain self-report measures, such as specific types of surveys or questionnaires like the Epworth Sleepiness Scale, can reveal useful information about the individual’s sleeping behaviors, daytime sleepiness, sleep attacks, cataplexy, etc.
- Narcolepsy and Substance Abuse
It appears that a large number of individuals with narcolepsy may develop depression, and individuals who develop major depressive disorder are at risk for the development of substance use disorders. However, individuals diagnosed with narcolepsy without a co-occurring psychological/psychiatric disorder do not appear to be considered to be at high risk for the development of a substance use disorder.
There is research that looks at the associations between impulsiveness and the symptoms of narcolepsy that has indicated that individuals with narcolepsy with cataplexy were found to be significantly more impulsive under certain cognitive tests than individuals with narcolepsy without cataplexy. Increased impulsivity is associated with an increased risk to develop substance abuse.
There is also research that indicates that a small number of individuals with sleep disorders also develop substance use disorders, such as alcohol use disorders, or abuse other substances to help them induce sleep; however, this research does not specifically apply to individuals with narcolepsy. Unless individuals diagnosed with narcolepsy also have depression or some other psychological/psychiatric disorder, these individuals as a group are probably not at a significantly increased risk to develop a substance use disorder; however, some individuals with narcolepsy may abuse alcohol and other medications in an effort to induce sleep.