Light exposure

Seasonal Affective Disorder: Longer days or nights can change your behavior

Seasonal affective disorder (SAD) is known as a type of depression that comes and goes in a seasonal pattern, characterized by feelings of sadness or depression in relation to seasonal changes.

It is also called “winter depression”. This is because SAD symptoms occur when the days are short and the nights are longer in the winter.

Bright light therapy has been shown to be an effective treatment for SAD, as well as non-seasonal depression, postpartum depression, and bipolar depression. However, the specific impact of seasonal changes in terms of day length and the brain’s exposure to light, at least at the cellular level, remains a mystery to the scientific community.

Now, a new study led by researchers in the United States has discovered the neurological mechanism behind this mysterious mental illness. The research team investigated the effects of SAD on the so-called suprachiasmatic nucleus or SCN, a small structure inside the hypothalamus of the human brain.

The team also found that SAD changes neurons in the paraventricular nucleus or PVN, an area of ​​the brain that is responsible for various bodily functions such as controlling metabolism, stress, growth, reproduction, the immune system, and other autonomic functions. These functions are generally involuntary, meaning that biological processes operate regardless of whether the living organism intends it to or not.

Seasonal affective disorder

(Photo: Photo by CHANDAN KHANNA/AFP via Getty Images)

In a new paper published in the journal Scientific advances on Friday, September 2, to confirm seasonal changes in the length of the day or photoperiod they affect many physiological functions. The groundbreaking study also supports the long-held notion that longer days or nights in summer and winter also have an impact on humans.

Conventional terminology has led to terms such as “gloomy weather” or “cold nights” that are associated with emotions or feelings associated with seasonal depression.

Also read: Antarctic fish change their behavior to adapt to changes in water temperature

SCN-PVN network

The most significant new finding brought forth by the new research is the discovery that the SCN-PVN network can be artificially manipulated. In particular, it changed the activity of some SCN neurons and successfully increased dopamine expression in the hypothalamic PVN network, according to David Dulcis, an associate professor at UC San Diego, as cited by News Medical.

Specifically, researchers at UC San Diego used a mouse model to show the process that affects neurons and neurotransmitters in response to day length, which triggers the aforementioned behavioral changes. Because mouse brains function almost similarly to humans, the researchers said that altered SCN neurons also affect brain activity and subsequent daily behavior.

A new mechanism

The authors of the study reportedly believe their findings provide a new mechanism to explain how the brain adapts to seasonal changes during exposure to light. Currently, early identification and diagnosis of SAD is a key medical best practice that physicians can perform.

According to the UK’s National Health Service (NHS), SAD can be difficult to diagnose because there are other types of depression that look like it.

However, the NHS says that a diagnosis of SAD can typically be confirmed when a person’s depression occurs at the same time or period every year for at least two years. In addition, the mentioned periods of depression are followed by periods without depression.

Related article: Bizarre ‘behavioral change’ observed in birds linked to climate change

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