Do you find yourself feeling sad, irritable and downright depressed during the winter months? Chances are, your mood can be linked to seasonal affective disorder (SAD) – a type of depression triggered by the change in seasons. During the winter – in the northern climates, at least – there is little exposure to natural light. You go to work when it’s dark and go home when it’s dark; sometimes you’re in an office with no windows and little natural light, and between all those things, it can affect your body’s chemistry, metabolism, and in some cases, your mood.

There’s a subset of people who are more sensitive to the change in seasons. It’s estimated one to three percent of the U.S. population is affected by SAD. According to Dr. Michael Murphy, national director for HCA’s Behavioral Health, psychiatrists have recognized SAD as a pattern in patients for many decades.

Words cannot do SAD justice, so we’ve created this video to explain. Take a look: