Regardless of their genetic propensity for depression, a recent study published in Translational Psychiatry concluded that people who spend around 1.5 hours every day exposed to outside light have the smallest risk of developing it.
In fact, the research found that there are higher risks of depression in those who spend not only less time than that outside but also more!
Millions of people around the world suffer from depression. Combining emotional, cognitive, and physical symptoms like melancholy, exhaustion, trouble focusing, changes in appetite or sleep patterns, and a lack of motivation are all part of it. In recent years, depression patients have become more prevalent all over the world.
It is thought that a combination of genetic and environmental factors contribute to depression.
Compared to children of parents who are not depressed, children of depressive parents have a 3-4 times higher risk of experiencing depression as well.
The likelihood of depression has been linked to certain genes as well as to variables like accessibility to outside light. It is well established that ambient light has an impact on critical bodily physiological functions.
When the skin is exposed to sunlight, a chemical process occurs that transforms a particular skin molecule into the active vitamin D that the body requires.
The stress hormone cortisol has been shown to be reduced by exposure to outdoor light as well.
Jing Lin, the study’s author, and her coworkers were interested in determining if exposure to outdoor light and the risk of depression were related.
They were trying to figure out the ideal amount of time spent outside to offset each person’s unique genetic propensity for sadness.
Data from the UK Biobank project was examined.
The UK Biobank is a sizable biomedical database that contains comprehensive genetic and medical data on about 500,000 people from the United Kingdom.
It was launched between 2006 and 2010 and has subsequently been expanded with new data.
Data from 380,976 White British participants, who ranged in age from 38 to 73 at the start of the trial, was evaluated for this study.
In a questionnaire, participants indicated how much time they typically spent outside in the summer as well as in the winter.
Through the use of a polygenic risk score, which took into consideration genes previously connected to the risk of depression, the genetic risk of depression was evaluated.
On the basis of the individuals’ medical data, depression was evaluated. In addition to this, the researchers looked at information on patients’ drinking and smoking patterns, physical activity levels, sleep patterns, BMI, numerous chronic illnesses, usage of vitamin D supplements, and a variety of other variables.
Results revealed that throughout the 12.5 years examined in the research, 3.58 percent of individuals had been given a depression diagnosis.
Compared to the rest of the research population, depressed participants tended to be older, more frequently women, and smokers.
Additionally, they were more likely to lack higher education, have a high BMI, sleep less, be exposed to greater levels of air pollution, and have a higher genetic risk of developing depression.
They also never or seldom used sunscreen.
Comparatively to people without depression, those with depression tended to spend more time outside on average.
However, subsequent investigation showed that the link between exposure to outdoor light and depression was not so simple.
Individuals who spent 1.5 hours outside on average each day—equivalent to 1 hour in winter and 2 hours in summer—had the lowest risk of depression.
Participants who spent either more or less were more likely to experience depression.
Less than that resulted in a 9 percent greater risk of depression, while more than 1.5 hours per day was associated with a 13 percent higher risk.
When combined with hereditary variables, the risk disparity rose to 34 to 35 percent.
Individuals with an intermediate degree of genetic risk for depression were more likely to experience the combined effects of genetic risk and outdoor light exposure.
The neuroendocrine system may suffer from a lack of outside light, according to the study.
The neurotransmitter serotonin affects our mood, and sunshine helps control its synthesis.
Lack of outside light can affect serotonin levels and cause mood swings, especially during particular seasons.
Inadequate exposure to outside light can also have a negative impact on vitamin D production, which has been linked to depression and its seasonal variations.
But why would more exposure to natural light be associated with a higher incidence of depression?
According to the researchers, this may be because extended exposure to UV radiation decreases the generation of melatonin, a hormone that aids in controlling our sleep patterns.
Our internal clock can be thrown off by low melatonin, which can worsen mental diseases like depression.
Long-term UV exposure can also increase the body’s synthesis of chemicals like IL-1 and IL-6, which are associated with inflammation and may contribute to depression.
The work makes a significant contribution to our knowledge of the scientific underpinnings of depression risk factors.
It should be emphasized, nevertheless, that the estimates of outdoor light exposure were made only using self-reported information. Furthermore, every research participant was a white British person.
Studies done on other populations utilizing more objective methods of determining outdoor light exposure could not provide the same results.