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Seasonal depression: when the light plays with the mood

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It's a fact: some people's moods turn gray with the onset of winter. Urban dwellers and women are particularly affected. However, seasonal depression can be easily treated.


Seasonal depression, or seasonal affective disorder, is a depression related to a decrease in natural light.

Serotonin production is decreasing

Still unexplained, in some people, a lack of light appears to decrease the production of serotonin, the brain's chemical messenger that regulates mood.

Then the mechanism of depression is activated: permanent sadness, especially in the morning; mood disorders (irritability, tendency to burst into tears, etc.); intense and unexplained fatigue; weight variation; persistent negative thoughts.

Not always taken seriously, seasonal depression is very disabling. The psychological suffering and the discomfort that it causes do not stop having an impact on the emotional and professional lives of those affected.

Some populations are more concerned

Women (75% of cases) are the most affected by seasonal depression. A large study (among 150,000 people) published in late 2017 by Scottish researchers confirmed this finding. More generally, this form of depression affects people with mood disorders or depression more easily. This complicates the diagnosis, since the seasonal episode is not always recognized as such when it occurs and, therefore, is not adequately treated.

Seasonal depression affects residents of the northern hemisphere and people of southern countries of the southern hemisphere, particularly those who have a lifestyle (subway, work, sleep) that exposes them less to daylight, the inhabitants of the cities and suburban dwellers than country dwellers.

Inuit populations, which inhabit the Arctic regions and therefore are subjected to polar night for several weeks, do not seem to be affected in the same way. Different hypotheses are put forward: her organism would have adapted to the lack of light over the centuries; her consumption of fatty fish (rich in omega-3 acids) would ensure good brain function despite the lack of light.

Recognize a seasonal depression

Two points are specific to seasonal depression: episodes of bulimia with a strong attraction to sugar that generally lead to weight gain;

hypersomnia, an overwhelming need to sleep that leads to long nights of sleep, but does not prevent you from feeling tired.

We all feel vague moments in the bad season, probably also related to the lack of light. But mild self-diagnosis of seasonal depressions is to downplay the actual illness.

This diagnosis can only be made seriously after an identical repetition of symptoms for two years in a row, without any other depressive events occurring. This is not easy as people with dysthymia (mood disorders) are also more easily affected by seasonal depression.

We must also be careful not to confuse the seasonal depression that recurs every year with the cyclical depressive phases of bipolar disorder.

Light therapy to help with seasonal depression

The solution to this form of depression is simple: take advantage of natural light for at least 30 minutes a day. Otherwise, the standard treatment for seasonal depression is light therapy (or phototherapy): the person is exposed for half an hour a day, upon waking, to a 10,000 lux lamp that reproduces natural sunlight. This treatment is applicable at home using specific lamps available on the market.

Very effective (70 to 80% of cases according to studies), phototherapy must be accompanied by an increase in physical activity and regular outings in the daylight. The superiority of this method over antidepressants (especially fluoxetine) has been demonstrated by large-scale comparative studies.

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