Bright Artificial Light Research Articles

Entrainment of human circadian rhythms by artificial bright light cycles.

Artificial bright light cycles (LD 8:16) of about 5000 lux during the light period were applied to two subjects in a temporal isolation unit, who had shown free-running circadian rhythms in sleep-wakefulness and rectal temperature. The circadian rhythms were successfully entrained by the artificial light cycle, but the phase relation of the rhythms to the light cycle was substantially different between the two subjects. The result indicated that the artificial bright lights are able to reset human circadian rhythms.

Midwinter insomnia in the subarctic region: evening levels of serum melatonin and cortisol before and after treatment with bright artificial light.

"Midwinter insomnia" (MI), mainly characterized by difficulties in falling asleep at night, is a common complaint during the period of obscuration or "dark period" north of the arctic circle. We hypothesize that MI is a result of a phase delay of the sleep-wake cycle due to insufficient exposure to daylight. In the present study based on this hypothesis, we wanted to find out whether otherwise healthy subjects with MI show abnormalities in the endocrine markers melatonin and cortisol late in the evening, and whether exposure to intensive light for one half hour in the morning for 5 days has any effect on the insomnia and on the endocrine variables. Nine subjects with typical MI were compared to eight controls. Before light exposure, the MI group had a significantly lower level of plasma melatonin in the evening than the controls, and a nonsignificant increase of plasma cortisol. After light exposure, the following results were seen in the MI group: sleep latency was moderately but significantly shortened, plasma melatonin increased to the same level as in the controls, and there was a nonsignificant increase of plasma cortisol. These results are largely in accordance with the predictions made from the phase delay hypothesis. However, other explanations cannot be ruled out.

Phototherapy of seasonal affective disorder. Time of day and suppression of melatonin are not critical for antidepressant effects.

Seasonal affective disorder is characterized by recurring cycles of fall-winter depression and spring-summer hypomania (or euthymia). In winter, depressed patients with seasonal affective disorder respond to daily treatments with five to six hours of bright artificial light in two to three days. They relapse two to three days after light is withdrawn. In this study carefully controlled experimental conditions were used to determine whether phototherapy acts via a photoperiodic mechanism in which the timing of light is critical for its therapeutic effect. Photoperiodism is a common regulatory mechanism in animal seasonal rhythms and depends for its effect on light-induced changes in the pattern of nocturnal melatonin secretion. The results reported herein of "skeleton photoperiod" experiments indicate that the efficacy of phototherapy may not depend on its timing or its effect on melatonin secretion.

Phototherapy for seasonal affective disorder in Alaska.

Six patients with seasonal affective disorder showed marked improvement in depressive symptoms after following three different 2-hour schedules of bright artificial light, and they relapsed when the light was withdrawn.

Refractory depression

AbstractRefractory depression is a poorly defined illness involving the persistence of symptoms of major depression or dysthymia over a prolonged period of time despite attempts at medical and psychotherapeutic intervention. The authors present a review of literature relevant to defining, evaluating and treating refractory depression. Medical illnesses, medications and substances of abuse may cause refractory depressions that fail to respond to conventional or extra‐ordinary treatments. Numerous medication strategies including the use of tricyclic and monoamine oxidase inhibitors, lithium, bright artificial light and electroconvulsive therapy constitute the major medical interventions available. Psychotherapies include cognitive, interpersonal, marital, psychoanalytic and group approaches. The clinician dealing with chronically depressed patients must be familiar with most of these diagnostic and treatment approaches in order to plan an effective long‐term intervention strategy for helping the patient to deal with the demoralization and seemingly overwhelming life stresses that frequently occur in refractory depression.

Use of light to treat jet lag: differential effects of normal and bright artificial light on human circadian rhythms.

Use of light to treat jet lag: differential effects of normal and bright artificial light on human circadian rhythms.

Antidepressant effects of sleep deprivation in bright and dim light.

In order to test whether exposure to bright artificial light at night is a necessary condition for the antidepressant response to sleep deprivation therapy, five patients were totally sleep-deprived on two separate nights, once in very bright light and once in nearly total darkness. During the day after the sleep-deprivation night patients were found to have responded equally well to sleep deprivation in both conditions. During the sleep-deprivation night, however, antidepressant responses may have been greater in the bright light condition. Thus, light at night is not necessary for the antidepressant response to sleep deprivation, but we cannot rule out the possibility that the effects of light exposure and sleep deprivation are additive or that exposure to light at some time after sleep deprivation begins (including during the following day) is necessary for the response.

Photoradiation therapy of gynecologic malignancies

Four patients with gynecologic tumors recurrent either to the vagina or skin were treated with photoradiation therapy. A cytotoxic effect on the tumor was achieved by injecting hematoporphyrin derivative intravenously followed by exposing the treatment area to light of 630 nm from an argon-ion pumped-dye laser 72 hr later. Of seven tumor sites which were treated, one was completely destroyed, two were diminished in volume by more than 30%, and no response was seen in four. Toxicity was limited to one episode of facial edema and first-degree burn after prolonged exposure to bright artificial light. Phototherapy might be a useful treatment of some gynecologic tumors which recur after standard attempts at control of disease.

Critical interval hypotheses for depression.

Two chronobiologic models are presented for the etiology of depression. The internal coincidence model suggests that a phase advance of the strong oscillator in reference to the weak oscillator causes depression. An external coincidence model suggests that depression is caused when the light/dark cycle or photoperiod provides too little illumination during a critical photosensitive interval, which might in turn occur early due to a phase advance. Thus, depression might be treated by drugs or other manipulations which delay the phase of internal circadian rhythms. Depression might also be treated with bright illumination during the critical photosensitive interval. Preliminary experiments suggest that bright artificial light does have antidepressant effects. The optimal times for light exposure and the most responsive patient groups have not yet been identified.

Effects of light on human melatonin production and the human circadian system

1. 1. Bright artificial light appears to have similar effects in humans as in other species. 2. 2. Bright light may therefore be used as a clinical research tool and as a therapeutic modality for treating certain biological rhythm disorders. 3. 3. Melatonin production appears to be a particularly useful “biological marker” for the human endogenous circadian pacemaker and the effects of light.

Light suppresses melatonin secretion in humans.

Bright artificial light suppressed nocturnal secretion of melatonin in six normal human subjects. Room light of less intensity, which is sufficient to suppress melatonin secretion in other mammals, failed to do so in humans. In contrast to the results of previous experiments in which ordinary room light was used, these findings establish that the human response to light is qualitatively similar to that of other mammals.