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Idiopathic Hypersomnia

Click here for the
Living with Idiopathic Hypersomnia Community Group

Idiopathic Hypersomnia (IH), sometimes referred to as Idiopathic Hypersomnolence, is a neurological sleep/wake disorder characterised by excessive sleep, chronic daytime sleepiness and cognitive dysfunction. IH is usually a debilitating, often lifelong, condition which profoundly affects work, education, relationships, and mental health. This is particularly the case for those without support. Idiopathic Hypersomnia is quite rare and the cause is poorly understood.

Most people can feel tired, fatigued and, at times, excessively sleepy, particularly when they do not get enough sleep. However, people with IH are different; they suffer from extreme sleepiness despite getting adequate or typically more than adequate hours of sleep.

Their sleep may be deep and uninterrupted, but it is not refreshing. Despite extraordinary amounts of good quality sleep, people with IH are in an almost constant state of sleepiness.


  • Overwhelming need for excessive sleep. Despite adequate and often extraordinary amounts of good quality sleep (e.g., 10–11 hours or more per night), people with IH still feel excessively sleepy during the day.

  • Chronic excessive daytime sleepiness, often resulting in long daytime naps.

  • Long and unrefreshing naps. Naps are usually more than one hour long and are typically not refreshing.

  • Extreme and prolonged difficulty waking up with an uncontrollable desire to go back to sleep. It is accompanied by confusion, irritability, and poor coordination, e.g., dropping things, walking into doorways. Speech may also be slow or slurred. It can also include automatic behaviour, i.e., performing tasks without consciously knowing it and not remembering you have done them, e.g., turning off alarm clocks or answering your phone.

  • Cognitive dysfunction (commonly referred to as ‘brain fog’): problems with memory, concentration and attention, and automatic behaviour.

In an attempt to combat the overwhelming sleep pressure, people with IH may develop ADHD-like symptoms such as fidgeting and talking a lot.

Additionally, autonomic dysfunction, a condition affecting the nervous systems control of automatic functions, is common in IH. This can manifest as headaches, dizziness upon standing, and trouble regulating body temperature.

Many people with IH regularly sleep more than 10–11 hours out of every 24. Despite good-quality sleep, it is not refreshing. Sleep is generally deep, and waking up can be extremely difficult. Sleep inertia, which is extreme difficulty awakening from sleep, can be so severe in people with IH that they sleep through multiple loud alarms and may even fall back to sleep several times. They often require humans to wake them and make sure they stay awake.

Sleep drunkenness is typically experienced with sleep inertia. Sleep drunkenness consists of confusion, disorientation, poor motor coordination, and slowness. People with sleep drunkenness may say irrational or unintentional things. Their speech may be slow or slurred. They may be clumsy, e.g., drop things, walk into doorways, or bounce off walls. Some people report sleep drunkenness lasting as much as 4 hours or more and that it can sometimes be more problematic than the chronic daytime sleepiness in IH. Those that experience sleep inertia or sleep drunkenness usually experience it every time they wake up, i.e., in the morning and when waking up from naps. People with IH commonly say that they never feel fully awake and that they struggle with a constant mental fogginess that can make carrying out even basic tasks difficult. Learn more about sleep drunkenness and sleep inertia here.

Symptoms frequently appear in the mid-to-late teens or early twenties. IH is a chronic disorder with limited treatment options. Medications do not treat the cause, are often not very effective, and can cause intolerable side effects. Even with medication, people with IH may struggle with ordinary day-to-day activities. Learn more about managing IH here.

Unlike in other sleep disorders, the sleep in people with Idiopathic Hypersomnia is normal; there are no disturbances that can account for these symptoms.


Diagnosing IH can be difficult as excessive daytime sleepiness can be caused by various disorders and/or conditions as well as numerous medications. A physical examination, medical tests, and a comprehensive medical history are necessary to rule out all other possible causes, including insufficient sleep. Sleep studies involving a Polysomnography (PSG) followed immediately by a Multiple Sleep Latency Test (MSLT) are also carried out to exclude other sleep disorders such as sleep apnea. Learn more here.

Treatment and Management
As the cause of IH is unknown, there is no cure nor medication specifically designed to treat it. Medications used to treat narcolepsy, including stimulants and wake-promoting medications, are prescribed to help manage daytime sleepiness. Unfortunately, these medications don't address all symptoms, such as cognitive dysfunction or the extreme difficulty waking up and sleep drunkenness.

Stimulant and wake-promoting medications can be helpful to relieve sleepiness for some people, but they are rarely effective long-term and generally don’t provide quality wakefulness. There are also potentially unpleasant side effects, which can include sleep deprivation, heart problems and anxiety. Learn more here.

Who does IH affect?
The pathogenesis of IH is unknown. Researchers have considered an autosomal dominant mode of inheritance because around 50% of people with IH have at least one family member who also has symptoms. It appears IH may be more common in females.

The prevalence of IH is thought to be 0.005%–0.3%, but due to a lack of epidemiological studies, biological markers, and misdiagnosis of the disease, the real prevalence is unclear.

Though the symptoms mainly begin in adolescence or young adulthood (typically between 15 and 30 years of age), it is not uncommon for there to be a delay of many years before an accurate diagnosis is made.

More information can be found at Hypersomnolence Australia.

Click here for information on the worldwide Idiopathic Hypersomnia Awareness Week® and for awareness posters you can share on social media.

Are you living with Idiopathic Hypersomnia?
Meet others you can relate to at Hypersomnolence Australia's regular Living with IH Community catch ups. The Living with IH Community meets monthly via Google Meet. If you would like to attend a meeting please register here. 
If you have any questions about the Living with IH community please email Michelle at
You can more information about the Living with IH Community on the Support Group page on Hypersomnolence Australia's website.

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Looking for a Facebook Support group?
We recommend the Idiopathic Hypersomnia Australia Facebook group. The Idiopathic Hypersomnia Australia group is a support and information sharing group run by the Living with IH Community Group Facilitator, Michelle Chadwick. The group is for people living in Australia and New Zealand who have been officially diagnosed with Idiopathic Hypersomnia. The group also welcomes parents of minors (under 18 years of age) who have been diagnosed with IH.

Read stories and perspectives by people living with Idiopathic Hypersomnia here

10th April 2022
Brisbane Convention and Exhibition Centre

On Sunday 10th April 2022, following the Sleep Health & Wellbeing Expo (on 9th April) we partnered with Hypersomnolence Australia for the Idiopathic Hypersomnia and Narcolepsy Education Day.

Researchers and clinicians in Australia receive very little or no education with regard to narcolepsy and disorders of hypersomnolence. This lack of knowledge and understanding has direct negative health outcomes for sufferers including delayed diagnosis and treatment. Our Education Day was a unique opportunity designed for medical and allied health care professionals, sufferers, and their families and friends to learn more about these disorders from our invited speakers and from each other.

Missed this event? There are videos of all of the info sessions. Go to Hypersomnolence Australia's YouTube Channel to watch them.

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