Insomnia in Chinese Medicine: The Heart of the Matter.

Chronic insomnia affects a significant proportion of the general population worldwide, and is associated with several serious medical conditions. From the Western scientific literature, hyper-arousal (on the cognitive-emotional, behavioral, autonomic, or central nervous system level) is a final common pathway involved in its pathogenesis. However, from a Chinese medicine (CM) perspective, it is the Heart, capitalized to denote the functional system as described in CM theory, that is the key organ involved in insomnia due to its role as the "seat of consciousness." This article explores how insomnia is understood from the CM perspective, in particular the role of the Heart, and some of the neurophysiological evidence that supports these ancient theoretical understandings. The potential role of the vagus nerve and its relationship with the (biomedical) heart and CM Heart is also examined. Finally, some of the evidence in association with mechanisms of action of acupuncture in insomnia, in particular its impact on cardiovascular variables associated with insomnia, is presented, along with findings of systematic reviews.