Medical Terminology


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Hypersomnia is distinct from idiopathic hypersomnia (IH). It is a broad medical term that generally refers to sleeping excessive amounts, excessive daytime sleepiness, or both. In some medical classification systems (such as the ICSD-3, which the Hypersomnia Foundation follows), the word “hypersomnia” is reserved to refer to several specific diagnoses, including idiopathic hypersomnia and the related sleep disorders. The related word “hypersomnolence” refers to the symptoms of long sleep and/or excessive daytime sleepiness, regardless of cause. These examples demonstrate the difference:

  • People have or are diagnosed with a hypersomnia (a disease). “My loved one has been diagnosed with a hypersomnia called idiopathic hypersomnia, which is often referred to as IH.”
  • People experience hypersomnolence (a symptom). “My loved one experiences severe, daily hypersomnolence; they’re overwhelmingly sleepy almost all the time.”

For more details, see Classification of Hypersomnias.