71 This has been shown with tryptophan deletion tests, where relapse after successful light therapy is induced, as well as the successful treatment of SAD patients by SSRIs.71 More direct evidence of the immediate effects of light on serotonin turnover in the brain has come from an in vivo study in healthy subjects: not only is serotonin turnover high in spring and summer and low in autumn and winter (the pattern following the hours of available sunshine), but serotonin turnover increases immediately after light exposure.73 Assuming that mood state #this website keyword# is at least partially linked to serotonin turnover, the conclusions are obvious: more light, better mood. The serotonin connection

suggests that a broader use of light therapy is indicated. A rapid response within a week in SAD does

not mean that other major depressive disorders will improve so fast: trials of light therapy over at least 4 to 6 weeks, as would be standard for a drug treatment trial, are required. Inhibitors,research,lifescience,medical There is already good evidence for efficacy in bulimia, preliminary evidence Inhibitors,research,lifescience,medical for usefulness in prepartum and postpartum depression (clinical indications where new nondrug therapies are sorely needed),74 and promising findings in major depression, particularly as an adjuvant (Table I). 74 Light is being recognized not only as a major zeitgeber necessary for our daily well-being (with applications in the work place and in architecture), but also as a ”drug“ that can be prescribed in dose, timing, and duration for specific diagnoses.71 An important step forward for the

clinician has been that all available randomized studies of light therapy for both SAD and nonseasonal depression are being analyzed for efficacy, and will soon be published in the Cochrane Library (www.cochrane.de). Inhibitors,research,lifescience,medical “Dark” therapy Single case studies of rapidly cycling bipolars have shown that extending darkness Inhibitors,research,lifescience,medical (or rest, or sleep) immediately stops the recurring pattern, which is a rather astonishing result in these therapy -resistant patients.38,39 Further support comes from recent findings that extended darkness (not rest and not sleep) in manic bipolar patients can control their symptoms within days (B. Barbini, personal communication). The pineal hormone melatonin is designated the “hormone of darkness.” Physiologically, it is important for timing the cascade of events initiating sleep in humans.20 The nocturnal onset of melatonin secretion else opens the gateway for sleep propensity, involving peripheral thermoregulatory mechanisms.75 The “warm feet effect” underlies its soporific action and use in a variety of sleep disorders.20 The few studies administering melatonin to depressed patients have indeed found improvements in sleep, but not in mood.76,77 Emerging therapies New drugs, such as agomelatine (a melatonin agonist and 5-HT2c antagonist), with a core action on circadian rhythms, are currently in development for the treatment of mood disorders.