145 healthy participants have used Philips EnergyLight (2500 lux) for at least 1 hour per day and at least 5 days per week at their workplace during 2 (out of 4) of 4-week periods (the other 2 4-week periods they used no extra light at their workplace). Even for the participants with no seasonal variation of mood and energy the bright light exposure has improved vitality and mood when compared to the weeks without extra light.