Vol 5 n° 4 - Chronobiology and Mood Disorders
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This issue of Dialogues in Clinical Neuroscience is devoted to circadian rhythms and related disorders. Many patients with psychiatric disorders show disturbances in circadian rhythms and frequently sleep disorders. These disorders are considered either to be the cause or the symptoms of the corresponding psychiatric disorder. Whether they be the cause or the effect, it is important to take them into con- sideration for treatment decisions. Specific treatments, such as melatonin, light therapy, advanced and delayed sleep phase, and sleep deprivation, are reported here. Chronobiology   (circadian,   ultrarapid,   and   seasonal rhythms) is an essential component of human and animal lives. Disturbances in these rhythms result in behavior abnormalities and mental and somatic symptoms. Exceptionally, in this issue two State of the art articles illus- trate the current knowledge of the complexity of circadian rhythms. In the first, Anna Wirz-Justice (page 315) refers to diurnal  variations  of  mood  and  sleep  disturbances  in depression, leaving open the question of its etiological sig- nificance. Antidepressant treatments, medication, sleep deprivation, and exposure to bright light (corresponding to sunlight) are discussed. The opposite of light—darkness— and the hormone melatonin are examined, as well as future aspects, which are delineated in an extensive manner. The second State of the art article by Alain Reinberg and Israel Ashkenazi (page 327) is more conceptualized, relat- ing biological rhythms to environmental factors as adap- tive phenomena to the movement of the earth. In this sophisticated text, they focus on human chronobiology and the problem of desynchronization, which can occur without clinical symptoms (which they call allochronism) or with numerous pathological symptoms (dyschronism). They describe diseases with chronic sleep disturbances, for example, night shift workers who are intolerant to desyn- chronization. The Basic research article by Paul Pévet (page 343) focus- es on the sleep hormone melatonin. The paper elucidates the role of melatonin in animals with special respect to cir- cadian and seasonal rhythms. The administration of exoge- nous  melatonin  shows  the  complexity  of  melatonin‘s actions. Depending on the dosage, the time of administra- tion, and the sensitivity of melatonin receptors, different effects are reported. Melatonin has various effects, which are mediated through the different melatonin receptors. Pharmacological treatment with melatonin or similar sub- stances has to consider this complexity. Two articles in this issue deal with chronobiological disor- ders and techniques of light therapy. In the Pharmaco- logical aspects article, Barbara L. Parry and Eva L. Mau- rer (page 353) focus on phototherapy and its possible mechanisms in various psychiatric conditions and subsyn- dromal states, including gender issues like premenstrual dysphoric disorder. It is a comprehensive article covering most of the existing relevant literature related to this topic. More clinical aspects are covered in the Poster by Ulrich Voderholzer (page 366) on sleep deprivation therapy, which is one of the most effective therapies for severe depression. Unfortunately, it is only short-lasting, but its effect can be prolonged   in   combination   with   pharmacotherapy, advanced sleep phase therapy, and light therapy. Predictors for the response to sleep deprivation therapy from brain imaging and endocrine studies are discussed. Sleep disorders are strongly related to disturbances of cir- cadian rhythms and are comprehensively described in the Clinical research article by Vivien C. Abad and Christian Guilleminault (page 371). They describe exactly the differ- ent forms of sleep disorders and present guidelines for treatment. Additionally, other circadian rhythm disorders are mentioned and options for treatment with chronother- apy and light therapy are given. Restless legs syndrome, periodic limb movement disorders, obstructive sleep apnea, narcolepsy, and parasomnia are comprehensively discussed. The second article to deal with light therapy is a Clinical research   article  from  Nicole  Praschak-Rieder  and Matthäus Willeit (page 389). It covers the treatment of mood and also seasonal affective disorder (SAD), which may be a subform of major depression, recurrent, or bipolar disorder. The current knowledge of the patho- physiology of SAD and the various treatments with bright light are presented as a first-line option for SAD. Recom- mendations for the general management of such disor- ders are given, also mentioning a combination of thera- pies with psychotropic drugs. 3 1 3 I n   t h i s   i s s u e . . .