Recently, the US National Renewable Energy Laboratory found that natural light increases human productivity, improves body function, normalizes the sleep-wake cycle, and provides additional strength. Scientists also note that daylight provides the mental and visual stimulation needed to regulate a person's daily biorhythms.
It's all about vitamin D, which is synthesized in our skin under the influence of ultraviolet rays, coming along with daylight. Lack of this vitamin can lead to a weakening of the immune system and an increased risk of developing cardiovascular diseases.
Of course, in winter we feel a significant lack of not only vitamin D, but also daylight itself. Not to mention the fact that not all workplaces are close to windows. In such a case, one can only advise to go out more often. Well, or ask the boss for a new job, telling him about the research of scientists and your ability to work.