Work by the window

In one office study, 104 workers spent four weeks under their usual lighting and four weeks under blue-enriched light, a whiter, cooler light. It was bluer, not brighter. Under the bluer light they said they were more alert and in a better mood, less tired in the evening, and slept better. Evidence: decent

Two limits. The lighting was purpose-built for the study, not an ordinary office lamp. And it was all self-reported: people rated how they felt, nobody measured their alertness.

A window and open blinds haven't been tested the same way. Daylight is both brighter and bluer than office light, so it's a related idea, and it's free. Evidence: worth trying For the morning version, see daylight in the first hour.