Accumulating evidence has proven that narcolepsy type 1 (previously narcolepsy with cataplexy) is caused by the loss of hypocretin-1 (orexin) neurons in the lateral hypothalamus [16,17,18], but patients with narcolepsy type 2 are found to have normal hypocretin levels, and its etiology remains unknown [19]. This evidence concerns the gene HCRT and narcolepsy without cataplexy.