“It's hard to tell where narcolepsy ends and where I begin.” – Nicki

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The Science of Narcolepsy

Knowing the cause of narcolepsy can help with understanding the symptoms.

States of Sleep and Wakefulness

People have separate states of wakefulness and sleep. There is one wake state, usually during the day, and two sleep states.

Wakefulness or wake: when a person is aware, alert, and can think clearly

Non-REM sleep: light to deep restorative sleep usually without dreaming

REM sleep: when dreams normally occur and most muscles are not active

Normally, the shifts from one state to another are clear and consistent, so that people experience one state at a time. For example, they are awake all day and sleep well at night.

I’m going in and out of dreams so fast that it can be difficult to distinguish a dream from reality.

Person living with narcolepsy, FDA Voice of the Patient*

Stories about living with narcolepsy are personal.

Listen to them now »

What are the symptoms of narcolepsy?

They may not be obvious »
What in the Brain Affects Sleep and Wakefulness?

Many chemicals in the brain play important roles in sleep and wakefulness, including hypocretin and histamine. During the day, hypocretin helps people stay awake and prevents non-REM sleep and REM sleep from occurring at the wrong time. Histamine plays a similar role in sleep and wakefulness.

When a person’s brain begins to lose hypocretin, sleep and wake can happen at the wrong time.

What Happens in People Living With Narcolepsy?

In most people with narcolepsy, hypocretin levels are decreased or absent. When these levels become too low, people are more likely to have cataplexy and severe sleepiness.

In narcolepsy, the separate states of wakefulness and sleep do not work properly, shifting often from one state to another. Aspects of sleep can interrupt wakefulness, and aspects of wakefulness can interrupt sleep. For example, parts of REM sleep, such as muscle weakness, can happen briefly during the day and cause cataplexy, or at night, interruptions from wakefulness can cause disrupted nighttime sleep.

* Quoted from the U.S. Food and Drug Administration, “The Voice of the Patient: Narcolepsy” report from June 2014, available at https://www.fda.gov/downloads/ForIndustry/UserFees/PrescriptionDrugUserFee/UCM402907.pdf. Approximately seventy (70) persons living with narcolepsy or their representatives attended "The Voice of the Patient" meeting in-person, and over fifty (50) persons provided input through the live webcast and polling questions. The quote is from a person living with narcolepsy, the name of whom is not published in the report. Although participants at this meeting may not fully represent the population living with narcolepsy, the FDA believes that the input received reflects a range of experiences with narcolepsy symptoms and treatments.

Performance of routine tasks without awareness or memory.

Difficulty focusing or concentrating.

Brief loss of muscle tone with retained awareness, often triggered by strong emotions.

Frequent shifts between different states of sleep and wakefulness at night.

The inability to stay awake and alert during the day; a constant need for sleep or unintentionally falling asleep.

A chemical in the brain that helps maintain wakefulness.

Vivid, realistic, and frightening dream-like events that occur when falling asleep.

Dream-like events that occur when falling asleep. Called hypnopompic hallucinations if they occur when waking up.

A chemical in the brain that helps maintain wakefulness and prevent non-REM sleep and REM sleep from occurring at the wrong time.

Unintentionally falling asleep due to excessive daytime sleepiness; “sleep attacks.”

Restorative sleep state with decreased muscle tone.

Occurs at night and includes vivid dreams; muscles are not active to prevent people from acting out dreams.

Daytime and evening habits to improve sleep.

Brief total loss of voluntary muscle control when falling asleep or while waking up.

People with type 1 narcolepsy can be diagnosed by their cataplexy or low levels of hypocretin.

The cause of type 2 narcolepsy is unknown.