Dawn simulation vs. bright light in seasonal affective disorder: Treatment effects and subjective preference

BACKGROUND

Studies comparing the efficacy of dawn simulation to conventional bright light for the treatment of seasonal affective disorder (in parallel groups) have yielded conflicting results. This crossover study investigated treatment outcomes and long-term treatment preference.

METHODS

Forty winter depressives were treated for a week with bright light (4.300lx for 30-45min shortly after awakening) or dawn simulation (gradually increasing light during the last 30min of sleep achieving 100lx before alarm beep, with the dawn simulator placed closer to the open eyes for a further 15min: 250lx). The depression level was self-rated using SIGH-SAD-SR.

RESULTS

Depression scores reduced similarly following bright light and dawn simulation: for 43.8% and 42.2% (medians), respectively; efficacy ratio was 23:17. The preference was also similar (21:19). Among those who preferred bright light, the most common reason was that they perceived the bright light to be more effective (19/21; it was more effective, p=0.0096; this subgroup tended to have more severe depression) and ease of use (6/21). Among those who preferred the dawn simulator, the reasons were a more "natural" action (9/19), device compactness and/or time-saving (10/19) and in 4 cases where bright light caused eyestrain.

LIMITATIONS

Not overhead naturalistic light for dawn simulation, self-rating of depression.

CONCLUSIONS

Dawn simulation is similarly effective to bright light in the treatment of winter depression. Patients with more severe depression tended to report greater improvement with bright light; in such cases, this would outweigh the non-clinical advantages of dawn simulation.

The human circadian pacemaker can see by the dawn's early light

The authors' previous experiments have shown that dawn simulation at low light intensities can phase advance the circadian rhythm of melatonin in humans. The aim of this study was to compare the effect of repeated dawn signals on the phase position of circadian rhythms in healthy participants kept under controlled light conditions. Nine men participated in two 9-day laboratory sessions under an LD cycle 17.5:6.5 h, < 30:0 lux, receiving 6 consecutive daily dawn (average illuminance 155 lux) or control light (0.1 lux) signals from 0600 to 0730 h (crossover, random-order design). Two modified constant routine protocols before and after the light stimuli measured salivary melatonin (dim light melatonin onset DLMOn and offset DLMOff) and rectal temperature rhythms (midrange crossing time [MRCT]). Compared with initial values, participants significantly phase delayed after 6 days under control light conditions (at least -42 min DLMOn, -54 min DLMOff, -41 min MRCT) in spite of constant bedtimes. This delay was not observed with dawn signals (+10 min DLMOn, +2 min DLMOff, 0 min MRCT). Given that the endogenous circadian period of the human circadian pacemaker is slightly longer than 24 h, the findings suggest that a naturalistic dawn signal is sufficient to forestall this natural delay drift. Zeitgeber transduction and circadian system response are hypothesized to be tuned to the time-rate-of-change of naturalistic twilight signals.

Phase advance after one or three simulated dawns in humans

A specially designed apparatus that can simulate the waveform of the dawn or dusk signal at any latitude and any day of the year has been shown to phase shift the circadian pacemaker in rodents and primates at a fraction of the illuminance previously used. Until recently, it was considered that rather high illuminances or rather long exposure episodes to room light were necessary to phase shift human circadian rhythms. This experiment shows that, under controlled conditions of a modified constant routine protocol, a single dawn signal is sufficient to phase advance the timing of the onset of secretion of the pineal hormone melatonin. The significant phase advance of salivary melatonin of 20 minutes, which is enhanced to 34 minutes after three consecutive dawn signals, is small, but appears to be of sufficient magnitude to entrain the human circadian pacemaker, which has an endogenous period of about 24.2h.

Evening administration of melatonin and bright light: interactions on the EEG during sleep and wakefulness

Both the pineal hormone melatonin and light exposure are considered to play a major role in the circadian regulation of sleep. In a placebo- controlled balanced cross-over design, we investigated the acute effects of exogenous melatonin (5 mg p.o. at 20.40 hours) with or without a 3-h bright light exposure (5000 lux from 21.00 hours-24.00 hours) on subjective sleepiness, internal sleep structure and EEG power density during sleep and wakefulness in healthy young men. The acute effects of melatonin, bright light and their interaction were measured on the first day (treatment day), possible circadian phase shifts were assessed on the post-treatment day. On the treatment day, the evening rise in subjective sleepiness was accelerated after melatonin and protracted during bright light exposure. These effects were also reflected in specific changes of EEG power density in the theta/alpha range during wakefulness. Melatonin shortened and bright light increased sleep latency. REMS latency was reduced after melatonin administration but bright light had no effect. Slow-wave sleep and slow-wave activity during the first non-rapid eye movement (NREMS) episode were suppressed after melatonin administration and rebounded in the second NREMS episode, independent of whether light was co-administered or not. Self rated sleep quality was better after melatonin administration whereas the awakening process was rated as more difficult after bright light. On the post-treatment day after evening bright light, the rise in sleepiness and the onset of sleep were delayed, independent of whether melatonin was co-administered or not. Thus, although acute bright light and melatonin administration affected subjective sleepiness, internal sleep structure and EEG power density during sleep and wakefulness in a additive manner, the phase shifting effect of a single evening bright light exposure could not be blocked by exogenous melatonin.

The hypothermic effect of late evening melatonin does not block the phase delay induced by concurrent bright light in human subjects

This constant routine study (n = 9 men) compared the phase delay of the circadian system induced by a single pulse of evening light (5000 lx at 2100-2400 h) in the presence or absence of exogenous melatonin (5 mg p.o. at 2040 h). On the treatment day, light and melatonin protracted and accelerated, respectively, the evening decline in core body temperature (CBT). Subjective sleepiness ratings showed parallel shifts, the earlier the decline in CBT, the sleepier. On the post-treatment day, light induced a phase delay in the mid-range crossing time of CBT decline independent of whether melatonin was co-administered or not. Subjective sleepiness was delayed in parallel. The phase delay of the circadian system by evening light appears to be independent of an immediate hyperthermic effect and is not mediated by melatonin.

The importance of full summer remission as a criterion for the diagnosis of seasonal affective disorder

From 1987 to 1994, seasonal affective disorder (SAD) has been diagnosed using the Rosenthal or DSM-III-R criteria. No major differences between them have been found, except that the DSM-III-R criteria were more stringent and difficult to implement. Little attention has been paid to differences in the criterion of the quality of improvement in summer. This study compared two groups of winter depressives characterized by complete or incomplete summer remission. Incomplete summer remission is associated with increased heterogeneity of the demographic and clinical profile of the disorder and a shift of this profile to that of classical depression. The data support clinical use of the DSM-IV criterion 'full remission' in the diagnosis of SAD.

The relation of sleep-wake patterns to seasonal depressive behavior

A sample of 1644 adults in Alaska, Chukotka, Yakutiya, Western Siberia and Turkmenistan were surveyed to examine the relationship between seasonal depressive behavior and sleep-wake patterns. Interviews included items derived from the Seasonal Pattern Assessment Questionnaire, a 20 item general depression scale, and a 40 item sleep-wake questionnaire designed to assess the underlying mechanisms which regulate the cycles of sleep and wakefulness. Results show that subjects who suffer from seasonal depressive behavior, at latitudes ranging from 38-66 degrees North, are characterized by a sleep-wake pattern including 1) difficulty waking in the morning, 2) a low capacity to be awake at unusual times (out of sync with normal circadian patterns) and 3) a lower quality of nighttime sleep. Subjects with high levels of general depression suffer many of the same sleep problems, but this is not due to the measured association between seasonality and other depression. Disturbances in sleep-wake patterns may help to expand our understanding of the pathogenesis of seasonal depressive behavior, but further research to differentiate it from general depression is required.

Diurnal and seasonal variations of melatonin and serotonin in women with seasonal affective disorder

In winters 1990-1991 and 1991-1992 women with and without seasonal affective disorder, winter type, were treated by light at 2500 lux either in the morning (0800h-1000h) or afternoon (1600h-1800h). In winter before light treatment, melatonin levels in serum in daytime (1200h and 1600h) were higher in patients compared to controls (p < 0.05). This difference disappeared in the summer or after light treatment in the winter. Also, light treatment and change in season resulted in a phase advance shift of melatonin rhythm in patients. The decline in melatonin levels correlated with the decline in specific SAD symptoms of hyperphagia and carbohydrate craving. In winter, neither patients nor controls showed significant diurnal variations in levels of whole blood serotonin. In both patients and controls, levels of serotonin were higher in summer as compared with winter, especially at 2000h. Our data suggest that elevated daytime melatonin can be a state marker of winter depression, and that seasonal change of photoperiod may also affect the circadian amplitude and daytime levels of blood serotonin.

Hemispheric language lateralization in seasonal affective disorder and light treatment

Thirty-seven patients with seasonal affective disorder (SAD) and 25 control subjects were given a concurrent task, the verbal-manual interference paradigm, as a measure of hemispheric language lateralization. In winter, depressed patients showed a symmetrical interference pattern and control subjects experienced greater overall disruption in right-hand tapping during concurrent verbalization. Patients showed a greater left-hand tapping decrement compared with control subjects. Light treatment decreased the decrement in tapping with the left but not with the right hand in patients. After treatment, patients did not differ from controls in dual task interference effects. Patients also showed no difference from controls in summer. The difference between depressed subjects and controls in performance measures of laterality suggests that winter depression is associated with a shift of laterality from the left to the right. The winter abnormalities appear to be normalized by bright light.