Seasonal affective disorder is a form of depression that increases in severity during the winter months. Many people might feel a little low as the days start to shorten and the weather turns colder but with SAD sufferers these feelings affect their functioning. They could feel very moody for a long period, become extremely irritable and seem to lose interest in their lives. Sometimes this makes it very hard for them to get out of bed in the morning to face the challenges of the day ahead. They also tend to eat more than normal with a, particularly strong desire to increase their intake of carbohydrates. This easily leads to weight fluctuation and other health issues.
Scientists are unsure over what exactly triggers SAD, but its association with the winters leads them to suspect that lower exposure to sunlight has an adverse effect on hormones. Also, it is possible that hereditary factors make certain individuals more susceptible to SAD.