Clinical applications of melatonin in circadian disorders

Chronobiological disorders and syndromes include seasonal affective disorder (SAD), total blindness, advanced and delayed sleep phase syndrome, jet lag, and shift work maladaptation. These disorders are treated by adjusting circadian phase, using appropriately timed bright light exposure and melatonin administration (at doses of 0.5 mg or less). In some cases, it may be necessary to measure internal circadían phase, using the time when endogenous melatonin levels rise.

Winter Depression: Integrating mood, circadian rhythms, and the sleep/wake and light/dark cycles into a bio-psycho-social-environmental model

The phase shift hypothesis (PSH) states that most patients with SAD become depressed in the winter because of a delay in circadian rhythms with respect to the sleep/wake cycle: According to the PSH, these patients should preferentially respond to the antidepressant effects of bright light exposure when it is scheduled in the morning so as to provide a corrective phase advance and restore optimum alignment between the circadian rhythms tightly coupled to the endogenous circadian pacemaker and those rhythms that are related to the sleep/wake cycle. Recent support for the PSH has come from studies in which symptom severity was shown to correlate with the degree of circadian misalignment: it appears that a subgroup of patients are phase advanced, not phase delayed; however, the phase-delayed type is predominant in SAD and perhaps in other disorders as well, such as non-seasonal unipolar depression. It is expected that during the next few years the PSH will be tested in these and other conditions, particularly since healthy subjects appear to have more severe symptoms of sub-clinical dysphoria correlating with phase-delayed circadian misalignment; critically important will be the undertaking of treatment trials to investigate the therapeutic efficacy of morning bright light or afternoon/evening low-dose melatonin in these disorders in which symptoms are more severe as the dim light melatonin onset (DLMO) is delayed with respect to the sleep/wake cycle (non-restorative sleep should also be evaluated, as well as bipolar disorder). The possibility that some individuals (and disorders) will be of the phase-advanced type should be considered, taking into account that the correct timing of phase-resetting agents for them will be bright light scheduled in the evening and/or low-dose melatonin taken in the morning. While sleep researchers and clinicians are accustomed to phase-typing patients with circadian-rhythm sleep disorders according to the timing of sleep, phase typing based on the DLMO with respect to the sleep/wake cycle may lead to quite different recommendations for the optimal scheduling of phase-resetting agents, particularly for the above disorders and conditions.

The phase shift hypothesis for the circadian component of winter depression

The finding that bright light can suppress melatonin production led to the study of two situations, indeed, models, of light deprivation: totally blind people and winterdepressives. The leading hypothesis for winter depression (seasonal affective disorder, or SAD) is the phase shift hypothesis (PSH). The PSH was recently established in a study in which SAD patients were given low-dose melatonin in the afternoon/evening to cause phase advances, or in the morning to cause phase delays, or placebo. The prototypical phase-delayed patient as well as the smaller subgroup of phase-advanced patients, optimally responded to melatonin given at the correct time. Symptom severity improved as circadian misalignment was corrected. Orcadian misalignment is best measured as the time interval between the dim light melatonin onset (DLMO) and mid-sleep. Using the operational definition of the plasma DLMO as the interpolated time when melatonin levels continuously rise above the threshold of 10 pglmL, the average interval between DLMO and mid-sleep in healthy controls is 6 hours, which is associated with optimal mood in SAD patients.

The circadian basis of winter depression

The following test of the circadian phase-shift hypothesis for patients with winter depression (seasonal affective disorder, or SAD) uses low-dose melatonin administration in the morning or afternoon/evening to induce phase delays or phase advances, respectively, without causing sleepiness. Correlations between depression ratings and circadian phase revealed a therapeutic window for optimal alignment of circadian rhythms that also appears to be useful for phase-typing SAD patients for the purpose of administering treatment at the correct time. These analyses also provide estimates of the circadian component of SAD that may apply to the antidepressant mechanism of action of appropriately timed bright light exposure, the treatment of choice. SAD may be the first psychiatric disorder in which a physiological marker correlates with symptom severity before, and in the course of, treatment in the same patients. The findings support the phase-shift hypothesis for SAD, as well as suggest a way to assess the circadian component of other psychiatric, sleep, and chronobiologic disorders.

Medication timing for the elderly: the impact of biorhythms on effectiveness

The concept of chronopharmacology has significant implications for drug delivery systems. Age and illness put the elderly at greater risk for adverse drug effects, and nurses caring for the elderly have a challenging opportunity to measurably improve the quality of their care by applying chronotherapeutic concepts. Pharmacologic chronotherapy is a developing science that holds much hope for increasing the effectiveness of drug therapy and for reducing the incidence of toxic drug reactions. Nurses who are aware of the principles on which chronotherapy is based are in a unique position to improve the effectiveness of pharmacotherapy for all clients. However, appropriate timing of medications is especially important among elderly clients whose physiological processes are altered or changed by age and chronic illness. In this article, the basis of chronotherapy is discussed, and several therapeutic applications are identified.

Treatment of delayed sleep phase syndrome

Delayed sleep phase syndrome (DSPS) is a common but little reported cause of severe insomnia. Affected individuals complain of difficulty falling asleep and difficulty awaking at socially acceptable hours. It results from a dysregulation of the circadian sleep-wake cycle. DSPS presents in clinically heterogenous ways as modulated by motivation, psychopathology, drug status, and treatment compliance factors. Patients respond variably to the range of possible treatments. Bright light treatment potentially corrects the circadian abnormality of DSPS. Other treatments reported to relieve some DSPS patients include schedule shifts, drugs, and vitamin and hormone treatments. The safety and efficacy of light treatment have not been conventionally defined, but available information suggests that it is ophthalmologically safe. At present, DSPS must be managed empirically by various methods.

Non-pharmacological treatment of sleep and wake disturbances in aging and Alzheimer's disease: chronobiological perspectives

Numerous studies indicate a deterioration of nighttime sleep and daytime cognitive performance in elderly people and Alzheimer patients. As a result of the increasing number of elderly people and Alzheimer patients in the western society, attention for these problems has grown. However, so far, the major research effort has been concentrating on the development of pharmacological therapies for an isolated age-related problem. In the present review it is argued that several age-related problems with sleep and wakefulness may reflect a dampening of circadian rhythm amplitudes. Non-pharmacological manipulation of circadian rhythms by means of various external stimuli appears to be effective in improving sleep and cognitive functioning in elderly people and Alzheimer patients.

Seasonal affective disorder, Part II: Phototherapy, an expanded role of the psychosocial nurse

The integration of neurobiology into the research and practice of psychosocial nursing is an imperative for the decade of the 1990s. This substantial goal probably will be achieved through the completion of smaller endeavors. This article is intended to be one such contribution. The purpose of this article are threefold. First, it will introduce the psychosocial nurse to the characteristics of Seasonal Affective Disorder (SAD). This article also will provide the psychosocial nurse with the putative biological basis of SAD and phototherapy. Finally, specific information regarding the therapeutic application of bright light is provided.

Seasonal affective disorder. Shedding light on a dark subject

Seasonal affective disorder (SAD) appears to be a disturbance of circadian rhythm caused by desynchronization between the solar clock and the human biologic clock during seasons of short photoperiods. The supplemental bright light of phototherapy resynchronizes the disturbed rhythm; however, a comprehensive theory to explain the mechanism of phototherapy is lacking. Future research on the action of melatonin and serotonin and the photochemical effect of light in relation to possible circadian rhythm disorders should help us to better understand and treat not only SAD but other conditions such as jet lag, premenstrual syndrome, eating disorder, and carbohydrate-craving obesity.