What is the science behind seasonal depression?

With the end of summer and the return to the autumn routine, between 5 and 25% of the population may suffer depressive symptoms with greater or less intensity or severity. Normally, these subside when the days begin to lengthen in spring.

These symptoms, such as melancholy, feelings of weakness or fatigue, changes in appetite, or difficulty maintaining attention and concentrating, have been given different names. For example, autumnal asthenia, seasonal affective disorder, or winter blues.

The prevalence of these conditions can vary depending on sociodemographic variables such as age, sex or latitude of residence, which can affect between 1 and 10% of the general population.

The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) collects it as the “seasonal pattern recurrent major depressive disorder.” This disorder is characterized by the existence of a regular temporal relationship between the appearance and remission of depressive symptoms at specific times of the year without the existence of psychosocial stressors.

To be classified within this type of disorder, these episodes must be consistent over time and overcome possible non-seasonal depressive episodes in the individual’s life.

The International Classification of Diseases also includes “asthenia” within the diseases related to malaise and fatigue. This symptomatological picture characterized by a feeling of weakness, lack of energy and both physical and emotional fatigue has a multicausal origin. Its course is usually adaptive in nature, that is, it responds to the body’s effort to adapt to some change of relative importance.

Why does seasonal depression appear?

In humans, some physiological processes are linked to environmental factors such as sunlight or the alternation between activity and rest. This explains that when we travel and change the time zone, for example, we have difficulties to adapt to the new schedule and we suffer from the known jet lag. The secretion of hormones or the synthesis of some vitamins such as Vitamin D are some of these processes.

The ritmos circadianos They are known as the internal clock of the human being, since they mark our level of activation throughout the 24 hours of the day. The light that the brain receives activates brain structures such as the hypothalamus or the suprachiasmatic nucleus. These regulate the secretion of hormones and neurotransmitters responsible for regulating energy throughout the day. These rhythms are closely related to the metabolism and synthesis of melatonin, body temperature and pattern of sleep.

Usually, during the night our energy is very low, especially between 3 and 7 in the morning. This allows our sleep to remain stable and deep in that time frame.

Around 10 in the morning, our body temperature is increased, which allows our energy and activation level to be at the highest point of the day. It is common that after this activation rise, we identify the afternoon “slump” (just after eating).

The increase in melatonin secretion that occurs with the decrease in light received by the brain favors that we experience a state of drowsiness before midnight. It is the process that allows us to fall asleep until the next day.

Some working hypotheses have led researchers to consider that the delay in the phases of circadian rhythms could be responsible for the development of this psychopathological picture.

In addition, both circadian rhythms and melatonin synthesis are directly influenced by the amount of light we receive, with autumn and winter being the seasons with the fewest hours of sunlight of the year.

How to prevent autumn from changing our mood

Apart from the use of antidepressant psychotropic drugs and beta-blockers, numerous scientific studies praise the phototherapy as a possible treatment for depressive symptoms, especially of a seasonal nature.

However, in recent studies no differences have been found in the melatonin levels of people with seasonal depression, refuting the true usefulness of phototherapy in these pathologies.

There is great agreement in the scientific community of the importance of ruling out the presence of a depressive picture that requires attention in itself. That is to say, we should not confuse major depressive disorders (throughout the year and that can be aggravated in autumn) with exclusively seasonal disorders (which occur only in autumn and winter).

Therefore, the psychological assessment it may be more than advisable. In any case, the psychotherapeutic contributions aimed at addressing depressive symptoms will favor less dysfunction of the picture.

On the other hand, the physical exercise It has proven to be a fundamental tool for the improvement of the depressive picture. This favors not only the general mood, but also contributes to the recovery of the social sphere of the person affected by this disorder.

Being such a multifactorial condition, the need to carry out a multidisciplinary therapeutic approach for the correct remission of symptoms and the prevention of their reappearance seems evident.

Monica Moreno Aguilera, Professor in Degree of Psychology. Health and Forensic Psychologist, Nebrija University

This article was originally published on The Conversation. read the original.

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