#hypersomnia  an inability to stay awake
  exclusion:  insomnia
  supertype:  sleep_disorder__sleepdisorder  a disturbance of the normal sleep pattern
  subtype:  catalepsy  a trancelike state with loss of voluntary motion and failure to react to stimuli
  subtype:  narcolepsy  a sleep disorder characterized by sudden and uncontrollable episodes of deep sleep; "he believes that narcolepsy is attributable to an inability to suppress REM sleep during waking"

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