Morning or evening bright light treatment of winter depression? The significance of hypersomnia.

In a randomized crossover design 19 patients with winter depression were treated with 7 days of bright morning light (6:00 to 8:00 AM) and 7 days of evening light (7:00 to 9:00 PM). Bright light in the morning reduced the Hamilton Depression Rating Scale score from 22.3 to 5.5; bright light in the evening decreased the Hamilton score from 21.0 to 12.2. Improvement in the depression as measured by the Hamilton Depression Rating scores was greater with morning light compared with evening lights. Hypersomnia was associated (p less than 0.05) with a superior response to morning light.