Home Self Esteem Seasonal affective disorder: when winter brings us down.

Seasonal affective disorder: when winter brings us down.


Autumn is coming, the bright days are ending , the trips to the beach or the countryside and sitting on a terrace to have a drink. The shorter days arrive the return to work , the rains and the cold . This change generally produces a change of mood in all of us until we adjust to the routine . But this situation produces a devastating change in mood for some people.

This seasonal change in mood is called seasonal affective disorder , although it is also known as seasonal depression or winter depression .

This disorder is characterized by the presence of symptoms:

General depression Specific to this type of depression
  • Hopelessness
  • Lack of energy
  • Concentration difficulties
  • Sadness
  • Irritability
  • Weight gain, caused by an increase in appetite, especially carbohydrates and sweets.
  • Drowsiness, due to increased secretion of melatonin.

All these symptoms begin to manifest themselves in autumn and become more acute in winter, disappearing at the beginning of spring.


The causes of seasonal depression are not entirely clear , but studies reveal that it is associated with changes in melatonin and serotonin levels .

Our biological clock is governed by changes associated with sunlight. When sunlight decreases, our biological clock senses that it is time to sleep and secretes melatonin, a hormone that helps us fall asleep and stay asleep at night. When sunlight is sufficient again, the biological clock stops the production of melatonin and we begin to wake up.

This is why one of the characteristic symptoms of this type of depression is drowsiness . People with seasonal affective disorder seem to have a biological clock that tells their brain that in winter there is never enough sunlight and therefore they secrete more melatonin.

Other studies reveal that this type of depression is more common in high latitudes , countries such as Finland, Denmark, Sweden or Norway maintain a high index of seasonal depression. These countries have very long nights in winter. For example, Helsinki capital of Finland has an average of 7 hours of light on winter days and in Lapland the sun does not set all winter.

On the other hand, seasonal affective disorder has also been related to the lack of sunlight in buildings . Many of the buildings in which we live or work, do not have sources of sunlight, but it is artificial light. Few people like this type of light to work, it is uncomfortable and tires us more. People with seasonal depression show symptoms of depression much more in these environments than in those with natural light.

Serotonin is a neurotransmitter that is produced in the brain and that is involved in the regulation of mood , it is synthesized from  tryptophan , an amino acid that we incorporate into our body through our diet.

The available serotonin contents are lower during the fall and winter months. This is a consequence of the increased activity in the elimination of this neurotransmitter. This elimination process increases when there is less sunlight. People with seasonal affective disorder are more sensitive to this serotonin removal process.

Serotonin, apart from being one of the neurotransmitters that regulate mood, is also involved in the regulation of appetite and satisfaction . This mechanism could explain why people with seasonal affective disorder have a greater  craving for carbohydrates and sweets in the autumn and winter periods. We could see it as a kind of “self-medication”, increasing carbohydrate intake would increase the level of tryptophan intake and therefore the precursor of serotonin synthesis.


This therapy consists of exposing the person affected by seasonal depression to a 10,000 lux light bulb for 30 minutes at the beginning of their day.


In this way, the biological clock is synchronized and melatonin is stopped secreting.


Sometimes this problem has to be reinforced with  psychological therapy to help the person regain their lost routines and habits.



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