Seasonal affective disorder (SAD) is a type of depression that comes and goes in a seasonal pattern. SAD is sometimes known as “winter depression” because the symptoms are usually more apparent and more severe during the winter. Some people with SAD may have symptoms during the summer and feel better during the winter.

The exact cause of SAD is not fully understood, but it’s often linked to reduced exposure to sunlight during the shorter autumn and winter days.

The main theory is that a lack of sunlight might stop a part of the brain called the hypothalamus working properly, which may affect the:

production of melatonin

production of serotonin

body’s internal clock (circadian rhythm)

Click the link below for more information….

Overview – Seasonal affective disorder (SAD) – NHS (www.nhs.uk)