If you’ve already enjoyed being in nature, you know a new benefit has been discovered: Spending an average of 1.5 hours a day outdoors can reduce the risk of depression, according to a study recently published in Translational Psychiatry, regardless of genetic predisposition”. The study found that both people who spent more time outdoors and those who spent less time had a higher risk of developing depression.
Depression is a common mental illness that affects millions of people around the world and is associated with emotional, cognitive and physical symptoms such as sadness, fatigue, difficulty concentrating, poor appetite or sleep and lack of motivation. In recent years, the number of cases of depression has increased worldwide.
Scientists around the world believe that a combination of genetic and environmental factors may be the main cause of depression. Children of parents with a history of depression are three to four times more likely to develop the disorder than children of nondepressed parents. Certain genes such as B3GALTL, FADS1, TCTEX1D1, XPNPEP3, ZMAT2, ZNF501 and ZNF502 have been associated with a higher risk of depression in previous studies.
the new ally
In addition to genetic factors, the availability of outside light is also associated with the risk of depression. External light plays an important role in the body’s physiological processes. When skin is exposed to sunlight, a chemical reaction takes place that converts a skinspecific molecule into active vitamin D, which is essential for the human body. In addition, there is a recent discovery that links stress to levels of the stress hormone (cortisol).
The study team, along with lead author Jing Lin, wanted to investigate the link between time spent outdoors and the risk of depression, taking into account individual genetic predisposition. Researchers analyzed data from the UK Biobank Project, an extensive biomedical database of genetic and health information from half a million participants in the UK.
Participants reported how much time they spent outdoors on a typical day in both summer and winter. Genetic risk of depression was assessed using polygenic risk scores that accounted for genes previously associated with depression. The medical records of the participants were used to assess the presence of depression. Data on smoking and drinking habits, physical activity, sleep duration, body mass index and other factors were also analyzed as they were considered relevant to the observation.
Now, a new study that took about 12.5 years to analyze found that 3.58% of participants were diagnosed with depression. These individuals exhibited characteristics such as older age and a higher frequency of being female and smoking compared to the rest of the study sample. In addition, they rarely or never used sunscreen, had low education, high body mass index, slept less, were exposed to higher levels of air pollution, and had a greater genetic predisposition to depression.
Interestingly, it has been observed that, on average, people with depression spend more time outdoors compared to people without the condition. However, further analysis found that the association between exposure to outdoor light and depression was ambiguous. The lowest risk of depression was found among people who spent an average of 1.5 hours a day outdoors, which corresponds to one hour a day in winter and two hours a day in summer.
Those who spent more or less time had a higher risk of developing depression. Participants who spent less time outdoors had a 9% higher risk, while those who spent more than 1.5 hours a day had a 13% higher risk. When combined with genetic factors, this risk difference increased to 3435%, especially in people with an intermediate genetic predisposition to depression.
The researchers suspect that the lack of external light can negatively affect the neuroendocrine system. Sunlight plays an important role in regulating the production of serotonin, a chemical that affects our mood. Lack of outside light can affect serotonin levels and lead to mood swings, especially at certain times of the year.
However, it is important to ask why being outdoors for longer is associated with an increased risk of depression. According to the same researchers, this may be because prolonged exposure to ultraviolet light decreases the production of melatonin, a hormone that regulates our sleep patterns, a decrease in which can disrupt our internal clock and contribute to psychiatric disorders such as depression. Prolonged exposure to UV rays can also stimulate the production of certain substances in our body, which can also promote depression.