Vol 9, No 3 - Chronobiology in Psychiatry
Past issues Contributors How to publish Contributions and comments Home
 
 
he view that living organisms are three-dimen- sional beings, with height, length and depth, might be cor- rect when applied to gross anatomy, but represents a sim- plified and misleading description of most aspects of physiology and biochemistry. Biology operates in the fourth dimension, ie, time, and the number and extent of time-related and oscillating bodily functions is huge: most physiological functions are coded or structured in time. This conclusion comes from clinical studies of a descrip- tive nature, as well as from in-vitro studies on isolated cells or cell groups from multicellular organisms, and on unicellular organisms.1 For example, in endocrinology, the extent of a cell secretory response depends on the inter- spike and interburst intervals from afferent axons.2 Physiological mechanisms have diverse durations and oscillation  frequencies,  from  nanosecond  changes  in membrane ion channel shifts or enzymatic reactions and protein synthesis, to electroencephalographic or electro- cardiographic waves, to ultradian rhythms of a few min- utes or hours, to longer circadian rhythms, and up to cycles that last a month, a season, a year, or even more. It has long been recognized that the incidence of disease in humans can show annual fluctuation. Meteorological conditions favor the spread of many infections during either the cold or hot or damp months. Centuries ago in France, the lack of vitamins in food during winter was a cause of visual impairment during early spring, described in poor people such as the French peasants. More recently, clinical and epidemiological studies have shown that given syndromes or disorders tend to occur more frequently at given astronomical times, for example myocardial infarc- tion during the very early hours of the morning.3 Although the role of astronomical time in the occurrence and the incidence of various disorders was recognized centuries ago, basic and medical research on biological clocks is only recent. In the 18th century, the French sci- entist  Jean-Jacques  Dortous  de  Mairan  (1678-1771) described a circadian rhythm in plant leaf movements S t a t e  o f  t h e  a r t T Biological clocks and the practice of psychiatry Pierre Schulz, MD Endogenous  biological  clocks  enable  living  species  to acquire  some  independence  in  relation  to  time.  They improve the efficiency of biological systems, by allowing them to anticipate future constraints on major physiologi- cal systems and cell energy metabolism. The temporal orga- nization of a given biological function can be impaired in its coordination with astronomical time or with other bio- logical functions. There are also external conditions that influence biological clocks. This temporal organization is complex, and it is possible that a series of psychiatric dis- orders   and   syndromes   involve   primary   or   secondary changes in biological clocks: seasonal and other mood dis- orders, premenstrual syndromes, social jet lag, free-running rhythms, and several sleep disorders are among them. In this review, we describe the main concepts relevant to chronobiology and explore the relevance of knowledge about biological clocks to the clinical practice of psychiatry.   © 2007, LLS SAS Dialogues Clin Neurosci. 2007;9:237-255.Keywords:  chronobiology; circadian rhythm; ultradian rhythm; human study;
psychiatric disorder Author  affiliations:  Unité  de  psychopharmacologie clinique, Hôpitaux Universitaires de Genève, Chêne-Bourg, Switzerland Address for correspondence: Pierre Schulz, MD, Médecin-chef, Unité de psycho-pharmacologie clinique, Hôpitaux Universitaires de Genève, Domaine Belle-Idée, 1225 Chêne-Bourg, Switzerland (e-mail: pierre.schulz@hcuge.ch) Copyright © 2007 LLS SAS.  All rights reserved www.dialogues-cns.org