Melatonin, sleep, and circadian rhythm disorders.

In the 1970s and early 1980s, neuroendocrinology was viewed by many neuroscientists as a ""window to the brain" to an understanding of brain function." In psychiatry, many have viewed sleep physiology as a window in biological psychiatry. This is, in part, because sleep is one of the few easily quantifiable functions of interest to psychiatrists. Melatonin is a hormone with powerful effects on behavior particularly circadian and sleep behavior. In contrast with other hormones, the pathophysiology and pathology of abnormal melatonin secretion is poorly understood. In this article, we document the well-established phase-shifting and sleep-promoting effects of melatonin and discuss some implications for neuropsychiatrists when the neurophysiology of melatonin goes array. It is both striking and in some ways not surprising that the majority of patients with phase delay syndrome described in our research studies have been misdiagnosed as having depression. The reason for this is elucidated in this article and the information concerning this condition may be helpful to many who are relatively unfamiliar with this particular sleep disorder. We can anticipate that patients with specific neurological disorders may have changes in their melatonin secretion and future research, for example in patients with head injury and conditions such as retinitis pigmentosa may be the basis for reviews a few years hence.