Idiopathic hypersomnia and chronic fatigue syndrome are often confused due to overlapping symptoms. But beneath some shared experiences, these conditions are very different.

Idiopathic hypersomnia is a chronic sleep-wake disorder that belongs to a group of conditions known as central disorders of hypersomnolence. It involves excessive daytime sleepiness despite getting enough good quality overnight sleep.

Chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis, is a multisystem disease that causes severe fatigue, impaired thinking ability, body aches and pains, and a variety of other physical symptoms.

Both idiopathic hypersomnia and CFS can involve unrefreshing sleep and the experience of daytime tiredness despite getting plenty of rest. But even in these similar symptoms, differences can happen.

Idiopathic hypersomnia and CFS are not the same condition. They are separate diagnoses, although they have some surface similarities.

Both conditions can have the following features:

  • tiredness despite adequate rest
  • general fatigue
  • unrefreshing naps
  • impaired thinking ability
  • poor body temperature regulation
  • fluctuating symptom severity
  • headaches
  • depression
  • dizziness or loss of balance

However, idiopathic hypersomnia and CFS are more different than similar.

Underlying causes

The exact causes of idiopathic hypersomnia and CFS aren’t well understood, but what is known about them suggests that they have different underlying mechanisms.

Idiopathic hypersomnia is a sleep-wake disorder, which means it’s caused by disruption in the processes responsible for regulating your sleep cycles.

Because it’s a central disorder of hypersomnolence, changes in central nervous system function are the suspected cause of sleep cycle disruption in idiopathic hypersomnia. Overall, it’s considered a neurological condition.

CFS is not a sleep-wake disorder, although sleep disturbances can be a symptom for some people.

CFS is a multisystem disorder that is believed to have complex underlying causes related to genetics, changes in immune system function, infection, oxidative stress, hormones, and neuroinflammation.

Fatigue vs. excessive daytime sleepiness

In idiopathic hypersomnia, the primary symptoms are excessive daytime sleepiness and an irresistible urge or need to sleep despite having slept well the night before. Excessive daytime sleepiness is not the same as fatigue, which is the primary symptom of CFS.

Fatigue” is a broader term in CFS that describes a physical and mental state of being exhausted or worn out. It may cause you to feel tired and want to take a nap, but it’s not necessarily the same as being unable to resist sleep, as in idiopathic hypersomnia.

Fatigue and other CFS symptoms are known to get worse with physical or mental exertion, which is not a characteristic of excessive daytime sleepiness in idiopathic hypersomnia.

Idiopathic hypersomnia can cause general fatigue, and CFS can cause excessive daytime sleepiness, but they are not core diagnostic symptoms.

Body-wide symptoms

CFS features more body-wide symptoms than idiopathic hypersomnia.

CFS can affect your eyes, digestive system, joints, muscles, skin, lymph nodes, throat, and many other parts of your body.

Idiopathic hypersomnia is primarily a sleep condition. Its symptoms focus on experiences during waking up and falling asleep, though it can sometimes come with physical challenges such as headaches and dizziness or lack of balance.

Non-sleep-related symptoms are less common in idiopathic hypersomnia.

When you compare their symptoms, the differences between idiopathic hypersomnia and CFS become clearer.

Idiopathic hypersomnia symptoms

  • excessive daytime sleepiness
  • long, unrefreshing naps, usually lasting more than an hour
  • prolonged nighttime sleeping, typically for more than 9 hours
  • sleep inertia, difficulty waking, and disorientation/confusion during sleep-wake transitions
  • hyperactivity as a method of staying alert
  • impaired thinking ability
  • automatic behaviors (performing tasks without full awareness of them)
  • sleep hallucinations
  • sleep paralysis
  • headaches
  • dizziness or instability
  • poor body temperature regulation
  • depression

CFS symptoms

  • severe fatigue that is not the result of activity, is not relieved with rest, and was not present before you became ill
  • symptoms that worsen after physical or mental activity
  • sleep disturbances such as trouble falling asleep or staying asleep
  • unrestorative sleep
  • impaired thinking ability
  • orthostatic intolerance (physical symptoms that worsen when sitting or standing)
  • body aches and pains
  • headaches
  • joint swelling or redness
  • swelling of lymph nodes
  • sore throat
  • digestive issues
  • muscle weakness
  • allergies
  • lack of body temperature regulation
  • shortness of breath
  • irregular heartbeat
  • numbness or tingling in your face, hands, or feet
  • vision changes
  • chills and night sweats
  • psychological symptoms such as depression, mood swings, anxiety, and panic attacks
  • dizziness

Yes, it is possible to have both idiopathic hypersomnia and CFS.

Because they are separate conditions with different underlying causes, you might experience them as comorbid conditions (conditions you have at the same time).

Research suggests that as many as 56% of people living with CFS also have a sleep disorder.

Treatment is another area where idiopathic hypersomnia and CFS differ.

Treatment for idiopathic hypersomnia includes medications, particularly the wakefulness-promoting medication modafinil. Lifestyle changes, sleep schedule changes, and behavioral therapy may be helpful for some people but aren’t considered generally effective.

Treatment for CFS is far more diverse. It typically involves a multidisciplinary approach and a custom treatment plan based on your specific symptoms and their severity.

Treatments used in CFS include:

Your doctor may prescribe different medications based on your specific symptoms. Because CFS can vary significantly from person to person, what works for one person may not be as effective for another.

Idiopathic hypersomnia and chronic fatigue syndrome (CFS) share symptoms such as daytime fatigue, headaches, and unrefreshing sleep, but these two conditions are more different than alike.

Idiopathic hypersomnia is a sleep-wake disorder with possible neurological causes, while CFS is a multisystem disease that may be linked to factors such as genetics, immunity, infection, and oxidative stress.

You can have idiopathic hypersomnia and CFS at the time same, but the two conditions require different treatment approaches.