SAD, Seasonal Affective Disorder

By Cristiano Antonino Last updated Feb 23, 2023

Hippocrates was the first, in 400 BC, to describe a depressive disorder linked to seasonality and, in the 2nd century BC, Greco-Roman doctors used to treat depression with exposure to sunlight directly in the eyes

Pinel and his student Esquirol (1845) were instead the first to distinguish the subtypes of winter and summer depression, but only in 1984 Rosenthal and colleagues described the diagnostic criteria of the so-called “Seasonal Affective Disorder” (SAD), characterized by depression in autumn and winter and periods of well-being in spring and summer.

SAD is a chronic disease that presents cyclical depressive episodes. Its most common symptoms are:

hypersomnia or insomnia
hyperphagia (with a particular preference for carbohydrates), with consequent weight gain
mental and physical tiredness
lack of energy
difficulty concentrating
general sense of confusion
irritability.

Seasonal affective disorder in DSM-IV

Although seasonal affective disorder has been widely recognized by the scientific community, however in the DSM-IV it did not appear as an autonomous nosographic category, but rather as a modality of course of mood disorders; from a clinical point of view, the symptoms that characterize patients with SAD are among the depressive manifestations that the DSM-IV described as “atypical”.

In fact, in patients with SAD, the mood, despite being depressed, is reactive (i.e. those affected are able to cheer up when faced with positive events, see DSM-IV).

Furthermore, the deflection of the tone of mood is typically accentuated in the evening hours; other “atypical” depressive symptoms found in patients with this pathology are hyperphagia, weight gain, hypersomnia, anergy and lethargy.

Based on the course, two forms of SAD (Seasonal Affective Syndrome) are distinguished: the “winter form” and the “summer form”

In the “winter form”, which represents the prevailing presentation, the depressive symptoms begin during the autumn season, reach their maximum intensity during the winter season and partially or totally resolve at the beginning of the spring season.

In the “summer form”, instead, the depressive episodes occur at the beginning of the spring season, reach their peak in the summer period and are resolved at the beginning of the autumn season.

As previously mentioned, until the last edition of the DSM, this disorder was not classified as a specific nosographic entity, but as a simple form of depression with a cyclical and regular trend.

In the most recent edition of the Manual (DSM-5), however, Seasonal Affective Disorder is described as a real diagnostic category and treated as such.

Several theoretical models have been developed that can explain the pathophysiology of SAD, but only recently has the question arisen as to what really can be the cause of moodiness, sadness, melancholy or depression in some people, precisely during these times of the year .

Perhaps researchers at the University of Copenhagen managed to answer the question, with a study whose results were presented at the XII International Conference on Neuropsychopharmacology in London.

The problem, according to what emerged from the studies of Dr. Brenda Mc Mahon and colleagues, would be to be found in the levels of serotonin production, which would change according to the seasons and the amount of light present.

People who develop SAD would therefore have a problem with serotonin and levels of SERT, the transporter of this neurotransmitter, not coincidentally also called the good mood hormone.

To look at what happens in people’s brains, the researchers recruited 11 people with SAD and 23 healthy volunteers for comparison.

Using Positron Emission Tomography (PET), they performed brain scans and were able to observe significant summer-to-winter differences in SERT levels in patients suffering from SAD.

Notably, volunteers with SAD had higher levels of SERT in winter months, which correspond to greater serotonin removal in winter, whereas this was not the case with healthy volunteers.

According to the researchers, these findings confirm what others have previously suspected.

“We believe we have found the way the brain transforms when it has to regulate serotonin as the seasons change,” explained Dr. Mc Mahon. “The serotonin transporter (SERT) carries serotonin back into nerve cells where it is not active, so that the higher the SERT activity, the lower the serotonin activity.

“Sunlight keeps this setting naturally low,” adds the researcher, “but as the nights lengthen during autumn, SERT levels rise, resulting in a decrease in active serotonin levels.

Many people are not really affected by SAD, and we have found that these people do not have this increase in SERT activity, so their active serotonin levels remain elevated throughout the winter.”

However, Seasonal Affective Disorder is quite common

About 20% of the American population suffers from it and about 12 million people in Northern Europe alone.

«We know that a balanced diet, reducing caffeine intake and getting some physical exercise can help, as well as spending as much time as possible outdoors, because even when it’s cloudy the light is always higher than indoors .

It is certainly a disorder that should not be underestimated and should also be treated with the support of trained and competent specialists», concludes Dr. Mc Mahon.