Seasonal depression
La seasonal depression, or Seasonal Affective Disorder (TAF), is depression related to lack of natural light. In order to medically speak of seasonal depression, this depression must occur at the same time each year, in autumn or winter, for at least 2 consecutive years, and that it lasts until the following spring.
During the winter period, the days are short and the brightness less intense. This would drop from 100 lux (unit of measurement of luminosity) on sunny summer days to sometimes barely 000 lux on winter days.
Who is affected?
In Canada, about 18% of people experience a ” winter blues »26 characterized by a lack of energy and one moral more fragile. Some individuals experience this phenomenon more intensely. Achieved a true seasonal depression, they may have difficulty carrying out their usual activities. This is the case for 0,7 to 9,7% (36) of the adult population in North America.
In Europe, studies of seasonal depression concern 1.3 to 4.6% of the population. But the method of calculation depends on the objective criteria.
The majority, between 70 and 80% of those affected are women. Children and adolescents are more rarely affected.
The further one moves away from the equator, the more the number of people affected increases, because the number of hours ofsunshine fluctuates more during the year. For example, in Alaska, where the sun does not rise at all for more than 1 month during the winter, 9% of the population suffers from seasonal depression.1.
In people with classic depression or bipolar disease (with depressive episodes), depression is seasonally exacerbated in 10 to 15% of those affected.
As with classic depression, symptoms of seasonal depression can get worse to the point of leading to suicidal thoughts.
Seasonal depression in summer? Some people have seasonal depression in the height of summer. This may be due to the heat, that are sometimes difficult to bear or strong light. No specific treatment has been designed for people with seasonal summer depression. Doctors offer standard treatment for depression (psychotherapy, antidepressant drugs). Some people manage to relieve their symptoms by using an air conditioning system and reducing the ambient light in their place of residence, or by traveling to temperate regions.25. |
Causes
The Dr Norman E. Rosenthal, psychiatrist and researcher at the National Institute of Mental Health, was the first to demonstrate, in 1984, the link between light and depression34. He defined the seasonal depression. In fact, the “discovery” of this type of depression is inseparable from the invention of light therapy. It was by noting that exposure to broad-spectrum artificial light could benefit people suffering from depressive symptoms during the winter season that Dr. Rosenthal was able to demonstrate the role played by light on thebiological clock internal and mood.
Indeed, light plays an important role in the regulation of the internal biological clock. This controls several functions of the body according to very precise rhythms, such as wake and sleep cycles and the secretion of various hormones depending on the time of day.
After entering the eye, the light rays are transformed into electrical signals which, once sent to the brain, act on neurotransmitters. One of these, serotonin, sometimes called the “happiness hormone,” regulates mood and governs the production of melatonin, another hormone responsible for wake-sleep cycles. Melatonin secretion is inhibited during the day and stimulated at night. The hormonal disturbances caused by a lack of light can be severe enough to cause symptoms related to trough.
Degree of brightness: some benchmarks Sunny summer day: 50 to 000 lux Sunny winter day: 2 to 000 lux Inside a house: 100 to 500 lux In a well-lit office: 400 to 1 lux |