Dr Lance Workman, senior lecturer in psychology at Bath Spa University, says sunlight has a luminosity of around 100,000 lux.
However, office lighting is more likely to be within the 200-5009-00200-5009-00 lux range - meaning people who spend most of their time indoors are not getting the illumination they might need to maintain their mood.
"People who have got a very serious problem should think about phototherapy using a lightbox," he suggests.
High power LEDs could help in the construction of these by producing high levels of illumination without becoming hot.
Dr Workman adds that lighting levels are more important than exercise during the winter to help keep people feeling positive during the shorter, darker days.
But he suggests combining light exposure with physical activity for an all-round approach to boosting mood.
