Seasonal depression, also known as seasonal affective disorder (SAD), is a type of depression that occurs in a seasonal pattern, usually during winter months.

Researchers have long known that SAD is related to the lack of sunlight, but until recently, they didn’t know how this lack of sunlight could affect our mood. Now, scientists have found that a part of the brain called the suprachiasmatic nucleus (SCN) might be the key to understanding SAD.

What is the Suprachiasmatic Nucleus (SCN)?

The SCN is a small area within the hypothalamus, located in the center of the brain, just above the optic chiasm. It is known as the body’s master clock, as it controls the circadian rhythm, which is our internal 24-hour clock.

The SCN receives information about the day and night cycles from the eyes, which then synchronize the body’s biological functions, such as sleep-wake cycles, hormone secretion, and body temperature.

How Does the SCN Affect Mood?

Scientists have found that the SCN also plays a role in regulating mood. When the days get shorter, and there is less daylight, the SCN sends signals to the brain to produce more melatonin, a hormone that regulates sleep.

However, an excess of melatonin can cause feelings of lethargy, depression, and anxiety.

The Link Between the SCN and Seasonal Depression

Researchers believe that SAD occurs when the SCN, in response to the decreased sunlight, produces too much melatonin, which can lead to feelings of depression and lethargy.

This is why many people with SAD report feeling sleepy, moody, and have difficulty getting out of bed during the winter months.

How Researchers Discovered the Link Between the SCN and SAD?

Scientists have used a technique called functional magnetic resonance imaging (fMRI) to study the brains of people with SAD during different seasons.

They found that during the winter months, the activity in the SCN was much higher than in the summer months. They also found that people with SAD had less activity in the front part of their brain, which is involved in mood regulation. These findings support the hypothesis that the SCN plays a crucial role in the development of SAD.

Treatment for SAD

The most effective treatment for SAD is light therapy. Light therapy involves exposure to bright light, usually from a lightbox that simulates natural sunlight.

The lightbox provides a bright light that mimics natural sunlight, which can help regulate the circadian rhythm, reduce melatonin production, and improve mood.

Other treatments for SAD include cognitive-behavioral therapy (CBT), which helps people with SAD identify negative patterns of thinking and behaviors and replace them with positive ones.

Medications such as antidepressants may also be prescribed, but they are usually not as effective as light therapy for SAD.

Conclusion

SAD is a type of depression that affects many people during the winter months. Researchers have found that the SCN, which controls the body’s circadian rhythm, also plays a crucial role in regulating mood.

When the days get shorter, and there is less sunlight, the SCN produces excess melatonin, which can cause feelings of lethargy, depression, and anxiety. Light therapy is the most effective treatment for SAD, as it helps regulate the circadian rhythm and reduce melatonin production. Other treatments, such as CBT and medication, may also be helpful.