Hi everyone, this is John, continuing last week's topic.

What causes seasonal affective disorder (SAD)?

Researchers don`t know exactly what causes seasonal depression. The lack of sunlight may trigger the condition in people who are prone to getting it. The theories suggest:

Biological clock change: When someone has less exposure to sunlight, their biological clock shifts. This internal clock regulates mood, sleep and hormones. When it changes, people may have trouble regulating their moods.

Brain chemical imbalance: Brain chemicals called neurotransmitters send communications between nerves. These chemicals include serotonin, which contributes to feelings of happiness. People at risk of SAD may already have less serotonin activity. Since sunlight helps regulate serotonin, the lack of winter sun can make the situation worse. Serotonin levels can fall further, leading to mood changes.

Vitamin D deficit: Serotonin also gets a boost from vitamin D. Since sunlight helps us produce vitamin D, less sun in the winter can lead to a vitamin D deficiency. That change can affect serotonin and mood.

Melatonin boost: Melatonin is a chemical that affects sleep patterns. The lack of sunlight may stimulate an overproduction of melatonin in some people. They may feel sluggish and sleepy during the winter.

Negative thoughts: People with SAD often have stress, anxiety and negative thoughts about the winter. Researchers aren`t sure if these negative thoughts are a cause or effect of seasonal depression.

From the above factors, the most simple and effective way to improve the symptoms of SAD is to get enough sunlight.This is simply not realistic in cold and very short sunshine conditions,Now the arrival of SAD lamp solves this trouble for most people.SAD lamps can emit full-spectrum simulated sunlight, which can directly stimulate human eyeballs and promote brain chemical balance.Irradiate the SAD lamp for about 30 minutes at a fixed time every day, which can make the brain receive the signal of bathing in sunlight,So as to achieve the effect of alleviating changes in the biological clock. SAD symptoms will also improve relatively