Patients with IH do not experience cataplexy, sleep paralysis or hypnagogic hallucinations.
They wake in the morning feeling tired and drowsy, and it can take several hours before feeling alert.
They feel extremely sleepy and the need to take naps during the day is almost overwhelming. It is common to nap for 1-2 hours several times each day, but IH sufferers usually wake from these naps feeling unrefreshed.
Whilst research has provided us with several clues as to possible causes of IH, our understanding remains quite limited.