If you find your energy and focus level decrease with the amount of sunlight in winter, but your appetite and anxiety grow as the snow piles up, you might be experiencing seasonal affective disorder, or SAD.

SAD is a type of depression that follows a seasonal pattern. Although there is no confirmed cause, the condition is thought to be related to the effect seasonal variations have on our sensitive biological clock.

According to Canadian Mental Health Association, research in Ontario suggests that SAD affects about 2 to 3 per cent of the population. Another 15 per cent have a mild form of SAD known as the “winter blues.”

However, the term "winter blues" can be misleading, according to CMHA, because some experience SAD in the summer with symptoms like poor appetite, weight loss and sleeping troubles.

Take a look at CBC's interactive to find out more about the symptoms, diagnosis, cause and treatment of SAD.