Winter, which is drawing to a close, has been emotionally hard on some people. Cold, higher work or study load, less leisure... and few hours of daylight. The short winter days influence emotional discomfort. There is, in fact, even a clinical category for those who are especially affected by a lack of light: seasonal affective disorder, whose acronym in English corresponds precisely to the word "sad" in that language (seasonal affective disorder, SAD).
Sustained sun deprivation is capable of generating irritability, lack of energy, concentration problems or decreased sexual desire. One study set out to see if it might not be other environmental factors, such as pollution or temperature, that are connected to seasonal affective disorder. Seasonal changes in sunlight remained the protagonists.
The isolation in the houses in response to the pandemic put on the table the dependent relationship of people with the sun king. Thus, it has been reported that those with less access to sunlight remained less active during confinement and that the pattern of sleep and wakefulness was delayed due, in part, to less exposure to the sun in the morning.
“The sun performs the function of synchronizing our body, of indicating at what time of day we are. Like the rest of the animals that have lived on this planet, we have had to adapt to the fact that there is light and darkness. This entails the expression of one type of gene or another depending on the day or night”, explains Néstor Sánchez, psychoneuroimmunologist and co-founder of the company specialized in training and private clinical care Regenera.
Light regulates what is known as the circadian rhythm, an internal biological clock that marks those physiological patterns with a 24-hour cycle. Sleep is one of the controlled functions, to which others such as eating or physical activity are added.
To have the clock on time, the sun is essential, which ultimately controls the production of the hormone melatonin. For this reason, "morning exposure to the sun is interesting", in the words of Sánchez. And avoid light at night. Screens before bed are not good friends with circadian rhythms as they have the ability to alter them.
A set clock will facilitate the best quality of sleep and the opposite will have an impact on mood or on a cognitive level. Memory, for example, is one of many capacities affected by sleep deprivation. Who has not had numerous distractions after spending a bad night?
Regarding emotional well-being, beyond the negative part of the absence of sun, there is practically unanimity in affirming that exposure to it is related to numerous benefits when done prudently. Among its properties are: stress reduction, fewer depressive symptoms, better cognitive functioning or even greater satisfaction with work when it happens under the sun's rays.
“Looking at the sun for 15 minutes when we get up generates measurable changes in mood,” says Sánchez. One trial found that treatment with sunlight-simulating light for half an hour in the morning led to improvements in people with depression, both alone and in combination with the antidepressant fluoxetine.
Hence, the rays of the star have been used therapeutically throughout history. There are several experiments in which having sunny rooms in a hospital with psychiatric admissions led to patients being discharged earlier.
Sunlight has been shown to be able to trigger the release of serotonin, a central neurotransmitter in the brain and related to a positive state of mind. The absence of the first would decrease the level of the neurotransmitter, which has been related to the aforementioned SAD.
The positive effect on emotional well-being could in turn be mediated by the role of vitamin D. More than 90% of its total amount comes from exposure to sunlight and a lack of it has been associated with depressive symptoms. However, it seems that the relationship is not so clear.
“Vitamin D is precisely an immunoregulator and is involved in brain aging and mental pathologies. The exaggerated activity of the immune system, inflammation, has a lot to do with mood, although pathologies of this type do not always have to be related to inflammation”, says Sánchez.
The expert explains that the central hours of the day are better, especially in winter, to squeeze this vitamin from the sun's rays. “At dawn you will not synthesize vitamin D, but you will prepare yourself so that, at noon, when you are exposed to the sun, you will synthesize it better and burn less,” he affirms.
All light, however, has its shadow. Added to the bulk of the beneficial consequences is the evidence on the increase in violent suicides or the onset of episodes of disorders such as bipolar related to high heat stroke.