Gradual versus rapid dawn simulation treatment of winter depression

Bright light therapy has been shown to be effective in treating winter depression. Dawn simulation, a low-illuminance light that gradually increases in intensity while the person sleeps, decreased depression in an uncontrolled study. The present study compares a gradual dawn signal with a hypothesized placebo condition, a rapid dawn signal.

In a 4-week, randomized crossover design, nine patients with winter depression were treated with a gradual, 2.5-hour dawn simulation for 1 week and a rapid, 10-minute dawn simulation for 1 week. Both dawns had a maximum illuminance of 275 lux. At the end of each baseline week and treatment week, blind raters assessed the level of depression.

Hamilton Rating Scale for Depression mean scores significantly decreased for both the gradual dawn (17.7 to 5.9, p < .05) and the rapid dawn (17.2 to 7.0, p < .05) condition. The improvement was similar for both treatments. Early morning awakening was significantly (p < .01) more common with the gradual dawn (7/9) than with the rapid dawn (1/9) condition.

Depression decreased under both dawn simulations. Because the degree of improvement was similar, a placebo effect rather than the efficacy of dawn simulation might explain the results. However, a mere placebo effect is an unlikely explanation. The degree of improvement was similar to that shown in studies of bright light therapy and clearly superior to previous "placebo" control conditions. The side effects from the gradual dawn may have obscured a potential superiority of the gradual dawn over the rapid dawn.