Causes of Narcolepsy

The causes of narcolepsy are not well understood, and genetics have been ruled out except for a small number of cases (about 2%).

The normal process of falling asleep begins with a phase called non-rapid eye movement (NREM) sleep. During this phase, brain waves slow down considerably. After an hour or two of NREM sleep, brain activity picks up again, and REM sleep begins. Most dreaming occurs during REM sleep.

In narcolepsy, however, a person suddenly falls into REM sleep without first experiencing NREM sleep. This, along with certain other aspects of sleep that normally occur only during REM sleep happen at abnormal times, such as during the day.

Scientists believe that people with narcolepsy who begin to feel drowsy and then drop instantly into "dream sleep" may have imbalances in certain brain chemicals important in regulating sleep.