Narcolepsy is a sleep disorder that causes symptoms including excessive daytime sleepiness and cataplexy — sudden attacks of muscle weakness that may be triggered by strong emotion. Although narcolepsy is rare in the general population, it is more common among people with certain health conditions. These conditions can be related to narcolepsy in various ways. When someone has multiple health conditions at the same time, they are referred to as comorbidities.

Understanding common comorbidities of narcolepsy can help people recognize symptoms and talk to their doctors about treatment. Treating comorbidities may improve quality of life.

Some medications can cause dangerous interactions with narcolepsy treatments. It is important to ensure that your health care provider is aware of all medications you are taking, whether prescription, over-the-counter, vitamins, or herbal supplements.

Sleep Disorders

People with narcolepsy have an increased risk for experiencing other sleep disorders as well.

Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a sleep disorder that causes a person to stop breathing intermittently during sleep. Approximately 3 percent to 7 percent of the population has OSA. Like narcolepsy, OSA is associated with excessive daytime sleepiness. OSA is common in people with narcolepsy. In one study of 133 people with narcolepsy, 33 participants were also diagnosed with sleep apnea.

One problem arising from the frequent comorbidity of OSA is delayed diagnosis of narcolepsy. OSA can be diagnosed from an overnight polysomnography (sleep study), but some doctors may attribute excessive daytime sleepiness solely to OSA. This can result in treating sleep apnea without further testing for narcolepsy. Unfortunately, continuous positive airway pressure (CPAP), often does not alleviate the excessive daytime sleepiness caused by narcolepsy.

Restless Legs Syndrome

An estimated 7 percent to 10 percent of the U.S. population has restless legs syndrome (RLS), a neurological sleep-related movement disorder that causes uncomfortable sensations in the legs that become worse with rest or at night. A study published in the journal Sleep found that 14.7 percent of people with narcolepsy type 1 (narcolepsy with cataplexy) had restless legs syndrome, compared to 3 percent of those without narcolepsy​. About half of RLS cases are familial, meaning that the condition tends to run in families and is likely influenced by genetic factors.

RLS can cause disrupted sleep and make it difficult to nap. Some common treatments for restless legs syndrome can cause excessive daytime sleepiness as a side effect.

Periodic Limb Movement Syndrome

Also known as periodic limb movements disorder, periodic limb movement syndrome (PLMS) is another sleep-related movement disorder that can disrupt sleep and contribute to daytime sleepiness. PLMS causes rapid, repetitive twitching movements of the limbs during sleep. PLMS may occur with or without RLS in people with narcolepsy.

Psychiatric Disorders

The Burden of Narcolepsy Disease (BOND) study included 9,312 American adults diagnosed with narcolepsy. Published in 2013, the results of the BOND study found a high rate of psychiatric comorbidities compared with rates seen in people without narcolepsy. These comorbidities included mood disorders such as:

• Depressive and bipolar disorders
• Anxiety and attention disorders
• Psychotic disorders including schizophrenia

Accumulating research shows a relationship between sleep — especially REM sleep — and the regulation of emotions. Sleep is thought to help us protect and regulate the process of forming emotional memories and to contribute to healthy emotional reactivity. Sleep loss, on the contrary, makes it harder to modulate emotion.

Treatments for psychiatric disorders may make it more difficult for doctors to diagnose narcolepsy. Some treatments for psychiatric disorders, such as antipsychotic medication, may worsen narcolepsy symptoms. Stimulants prescribed for narcolepsy may also worsen psychotic symptoms.

Depression

In general, people with chronic health conditions are at higher risk for depression. In one study published in 2017, researchers surveyed 1,699 people who reported having narcolepsy. Depression was the most common comorbidity reported. According to the BOND study, people with narcolepsy were 22.8 percent more likely to develop depressive disorders compared with healthy controls.

Anxiety

The results of the BOND study showed that adults with narcolepsy are 13.1 percent more likely to have anxiety disorders than those without narcolepsy. People with narcolepsy may experience panic attacks or social anxiety related to fear of having a sleep attack in public or losing control of their bodies.

Bipolar Disorder

Among participants in the BOND study, those with narcolepsy had a 6.2 percent higher chance of having bipolar disorder. Formerly known as manic depression, bipolar disorder involves swings of mood, energy, and concentration that may be “up” or “down.” In a case study involving a 22-year-old male with narcolepsy, the treatments modafinil (Provigil) and venlafaxine (Effexor) worsened the subject’s manic episodes.

Schizophrenia and Other Psychotic Disorders

The BOND study found that people with narcolepsy had a 2.5 percent higher risk for schizophrenia — a mental health condition that affects how people think, feel and behave — and other psychotic disorders. While both schizophrenia and narcolepsy can cause hallucinations, people with schizophrenia are more likely to hear voices or sounds that aren't real. In contrast, the hypnagogic hallucinations (hallucinations that occur when falling asleep) in narcolepsy are usually visual. A case study about a 6-year-old female child with narcolepsy type 1 found she had been misdiagnosed with schizophrenia.

Metabolic Disorders

People with narcolepsy have a higher risk for developing metabolic disorders, which relate to energy, weight, and sexual development.

Obesity

Overweight and obesity are common in people with narcolepsy. Doctors diagnose overweight and obesity based on a person’s body mass index (BMI), which is a ratio of weight to height. A person is diagnosed as overweight if their BMI is between 25 and 29.9, and a BMI of 30 or higher is considered obesity. Overweight and obesity are risk factors for several health conditions, including heart disease, type 2 diabetes, high blood pressure, and sleep apnea.

Researchers have found that adults with narcolepsy tend to have a higher BMI than those without the condition. According to research in The Lancet, the BMI scores of males with narcolepsy are higher than 75 percent of the general male population, and the BMI scores of females with narcolepsy are higher than 61 percent of the general female population.

Children who develop narcolepsy often experience significant weight gain in the months following the onset of symptoms. According to research published in the journal Sleep, overweight and obesity are highly prevalent in children with narcolepsy, affecting 74 percent of them. According to the National Heart, Lung, and Blood Institute, around 20 percent of children in the U.S. have obesity.

A 2007 study of 13 people with narcolepsy found that those with narcolepsy type 1 had a lower metabolism and tended to eat less than people without narcolepsy. The researchers theorized that these changes in metabolism may be linked to low levels of hypocretin (also known as orexin), a brain chemical that plays a key role in the regulation of sleep and is deficient in people with type 1 narcolepsy.

Precocious Puberty

The development of narcolepsy in childhood is strongly associated with precocious puberty and obesity. (Precocious puberty is defined as puberty starting before age 8 in girls and age 9 in boys.) In a study published in 2013, researchers evaluated 43 children with narcolepsy. The rate of precocious puberty among participants was 17 percent, almost 1,000 times higher than the rate in the general population. The researchers concluded that narcolepsy in children is likely related to dysfunction in the hypothalamus, the region of the brain where hypocretin is produced, and its relationship to the production of hormones that mediate puberty and metabolism.

Type 2 Diabetes

According to The Diabetes Council, 33 percent of people with type 2 diabetes (also called diabetes mellitus) have disturbed sleep, which may include restless legs syndrome or periodic limb movement syndrome. Sleep disruptions in diabetes grow more severe if hyperglycemia (high blood glucose) is poorly controlled. Sleep deprivation also seems to contribute to increasing insulin resistance.

One theory suggests that hypocretin, the chemical deficient in people with narcolepsy type 1, has a protective effect against diabetes. Thus, the risk for developing diabetes rises in people with narcolepsy.

Talk to Your Doctor

Narcolepsy can increase the risk of developing several other health conditions, some of which can be serious, such as sleep apnea, mood disorders, and metabolic issues. If you or a loved one with narcolepsy is struggling to manage symptoms, or if new symptoms are emerging, it's important to speak with a doctor. Properly managing narcolepsy and addressing any related health concerns can greatly improve quality of life and reduce the risk of complications. Don’t hesitate to reach out to your health care provider for guidance and support.

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