Seasonal Affective Disorder (SAD): When the Lack of Light Causes Depression

It is a fact that some people’s mood turns gray in the winter because of the lack of light. A phenomenon that has been intensified this year by the coronavirus pandemic.



Serotonin production declines in the winter

Without explanation, in some people, the lack of light seems to reduce the production of serotonin, a chemical messenger in the brain that regulates mood.

Read Also: Depression: A Gene May Explain Why Women Are Most Affected

The mechanism of depression then kicks in: permanent sadness, especially in the morning; mood disorders (irritability, tendency to burst into tears…); intense and unexplained fatigue; weight change; persistent dark thoughts…

Not always taken seriously, Seasonal affective disorder (SAD) is highly disabling. The psychological distress and discomfort it causes are not without consequences for the emotional and professional lives of those affected.

Certain populations are more at risk of winter depression

Women in 75% of cases are the most affected by SAD. A large study published in 2018 confirmed this finding. More generally, this form of depression most easily affects people that are already suffering from mood band depressive disorders.  This complicates diagnosis because the seasonal episode is not always recognized as such when it occurs.

Seasonal depression mainly affects people who live in the northern hemisphere and have a lifestyle that exposes them less to daylight.

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Inuit populations, who live in the Arctic and are therefore exposed to the polar night for several weeks, do not seem to be affected in the same way as Europeans or Americans. Several hypotheses have been put forward: their bodies have adapted to the lack of light over the centuries; their consumption of oily fish (rich in omega-3 fatty acids) ensures that their brains function well despite the lack of light.

Why coronavirus may exacerbate the seasonal affective disorder

The health context of winter 2020-2021 with the epidemic associated with the new coronavirus can only accentuate this pattern of winter depression. The lack of light is felt all the more as we are encouraged to stay home as much as possible because of lockdowns which also creates social isolation that can make those most susceptible to this disorder more vulnerable.

The international COH-FIT survey, the first results of which were published in November 2020, found that states of stress, loneliness, and anger had increased among 20 to 25% of those surveyed. Women were more worried: 27% said they felt more stress (compared to 14% of men) and 23% reported greater feelings of loneliness (compared to 12% of men).

Read Also: Chinese Study Shows a Connection Between the Intestinal Flora and Depression

Recognizing Seasonal Depression

Two symptoms are specific to Seasonal Affective Disorder:

  • Bulimia episodes that can lead to weight gain.
  • Hypersomnia, an uncontrollable desire to sleep that leads to long nights of sleep but does not prevent you from feeling tired.

We all feel somewhat a little down during the winter season, probably also linked to the lack of light. But SAD is still a real mood disorder that should not be taken lightly

SAD can only be diagnosed after two consecutive years if the same symptoms recur but only if no other depressive events took place. This is not easy, as people with dysthymia (mood disorders) are also more easily affected by SAD.
It is also important not to confuse annual recurrent seasonal depression with the cyclical depressive episodes of bipolar disorder.

Read Also: University of Alabama: Depression Increases the Risk of Stroke

Light therapy for seasonal depression

The solution for this form of depression is natural light for at least 30 minutes a day. Otherwise, the standard treatment for Seasonal Affective Disorder (SAD) is light therapy (or phototherapy). When the person affected by SAD wakes they must be exposed for half an hour every day to a 10,000-lux lamp that mimics natural sunlight. This treatment can be done at home with special lamps available on the market: Make sure the model is medical grade.

Highly effective phototherapy (between 70 and 80% of cases) must be accompanied by an increase in physical activity (although this is more difficult this year due to the pandemic) and regular outings in daylight. In cases where bright light therapy is not effective, the use of short-acting antidepressants may be helpful.

Read Also: The COVID-19 Epidemic Tripled the Number of Cases of Depression in the US


Seasonality of depressive symptoms in women but not in men: A cross-sectional study in the UK Biobank cohort




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